From f7c9fe2ee7db171e56966b56cb303145e596f8e7 Mon Sep 17 00:00:00 2001
From: Sergej Nikolaev <kinolaev@gmail.com>
Date: Tue, 4 Dec 2018 01:47:37 +0300
Subject: [PATCH 1/8] Allow undefined for nullable graphql types

---
 packages/graphqlgen/src/generators/common.ts  |  39 +-
 packages/graphqlgen/src/source-helper.ts      |  11 +-
 .../flow/__snapshots__/basic.test.ts.snap     | 130 +++++--
 .../__snapshots__/large-schema.test.ts.snap   | 348 +++++++++++------
 .../__snapshots__/basic.test.ts.snap          | 208 ++++++----
 .../__snapshots__/large-schema.test.ts.snap   | 356 ++++++++++++------
 6 files changed, 730 insertions(+), 362 deletions(-)

diff --git a/packages/graphqlgen/src/generators/common.ts b/packages/graphqlgen/src/generators/common.ts
index 6d6ba078..9fef4c9a 100644
--- a/packages/graphqlgen/src/generators/common.ts
+++ b/packages/graphqlgen/src/generators/common.ts
@@ -193,25 +193,26 @@ export function printFieldLikeType(
   field: GraphQLTypeField,
   modelMap: ModelMap,
 ) {
-  const isNullable =
-    field.defaultValue === null ||
-    (!field.type.isRequired && field.defaultValue === undefined)
-
-  if (field.type.isScalar) {
-    return `${getTypeFromGraphQLType(field.type.name)}${
-      field.type.isArray ? '[]' : ''
-    }${isNullable ? '| null' : ''}`
-  }
-
-  if (field.type.isInput || field.type.isEnum) {
-    return `${field.type.name}${field.type.isArray ? '[]' : ''}${
-      isNullable ? '| null' : ''
-    }`
-  }
-
-  return `${getModelName(field.type, modelMap)}${
-    field.type.isArray ? '[]' : ''
-  }${isNullable ? '| null' : ''}`
+  const name = field.type.isScalar
+    ? getTypeFromGraphQLType(field.type.name)
+    : field.type.isInput || field.type.isEnum
+    ? field.type.name
+    : getModelName(field.type, modelMap)
+
+  const isRequired = field.type.isArray
+    ? field.type.isArrayRequired
+    : field.type.isRequired
+  const suffix = isRequired
+    ? ''
+    : field.defaultValue === null
+    ? ' | null'
+    : field.defaultValue === undefined
+    ? ' | null | undefined'
+    : ''
+  const type = field.type.isArray
+    ? name + (field.type.isRequired ? '' : ' | null | undefined')
+    : name + suffix
+  return field.type.isArray ? `Array<${type}>${suffix}` : type
 }
 
 export function getTypeFromGraphQLType(
diff --git a/packages/graphqlgen/src/source-helper.ts b/packages/graphqlgen/src/source-helper.ts
index 467541b7..4e14d1fe 100644
--- a/packages/graphqlgen/src/source-helper.ts
+++ b/packages/graphqlgen/src/source-helper.ts
@@ -46,6 +46,7 @@ type GraphQLTypeDefinition = {
 
 export type GraphQLType = GraphQLTypeDefinition & {
   isArray: boolean
+  isArrayRequired: boolean
   isRequired: boolean
 }
 
@@ -83,6 +84,7 @@ export type GraphQLUnionObject = {
 interface FinalType {
   isRequired: boolean
   isArray: boolean
+  isArrayRequired: boolean
   type: GraphQLInputType | GraphQLOutputType
 }
 
@@ -130,13 +132,15 @@ function extractTypeDefinition(
 
 const getFinalType = (
   type: GraphQLInputType | GraphQLOutputType,
-  acc: FinalType = { isArray: false, isRequired: false, type },
+  acc: FinalType = { isArray: false, isArrayRequired: false, isRequired: false, type },
 ): FinalType => {
   if (type instanceof GraphQLNonNull) {
     acc.isRequired = true
   }
   if (type instanceof GraphQLList) {
     acc.isArray = true
+    acc.isArrayRequired = acc.isRequired
+    acc.isRequired = false
   }
 
   if (type instanceof GraphQLNonNull || type instanceof GraphQLList) {
@@ -157,13 +161,16 @@ function extractTypeLike(
   type: GraphQLInputType | GraphQLOutputType,
 ): GraphQLType {
   const typeLike: GraphQLType = {} as GraphQLType
-  const { isArray, isRequired, type: finalType } = getFinalType(type)
+  const { isArray, isArrayRequired, isRequired, type: finalType } = getFinalType(type)
   if (isRequired) {
     typeLike.isRequired = true
   }
   if (isArray) {
     typeLike.isArray = true
   }
+  if (isArrayRequired) {
+    typeLike.isArrayRequired = true
+  }
   if (
     finalType instanceof GraphQLObjectType ||
     finalType instanceof GraphQLInterfaceType ||
diff --git a/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap b/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
index 124e009d..7d8f2a07 100644
--- a/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
+++ b/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
@@ -24,7 +24,7 @@ export type Query_CreateUser_Resolver = (
   args: Query_Args_CreateUser,
   ctx: Context,
   info: GraphQLResolveInfo
-) => User | null | Promise<User | null>;
+) => User | null | undefined | Promise<User | null | undefined>;
 
 export interface Query_Resolvers {
   createUser: (
@@ -32,7 +32,7 @@ export interface Query_Resolvers {
     args: Query_Args_CreateUser,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => User | null | Promise<User | null>;
+  ) => User | null | undefined | Promise<User | null | undefined>;
 }
 
 // Types for User
@@ -172,7 +172,7 @@ export const Mutation_defaultResolvers = {};
 
 export interface Mutation_AddMemberData {
   email: string;
-  projects: string[];
+  projects: Array<string>;
 }
 
 export interface Mutation_Args_AddMember {
@@ -205,7 +205,7 @@ export type AddMemberPayload_Json_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | Promise<string | null>;
+) => string | null | undefined | Promise<string | null | undefined>;
 
 export interface AddMemberPayload_Resolvers {
   json: (
@@ -213,7 +213,7 @@ export interface AddMemberPayload_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 }
 
 export interface Resolvers {
@@ -317,21 +317,27 @@ export type Query_Custom_nullable_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Number | null | Promise<Number | null>;
+) => Number | null | undefined | Promise<Number | null | undefined>;
 
 export type Query_Custom_array_nullable_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Number[] | null | Promise<Number[] | null>;
+) =>
+  | Array<Number | null | undefined>
+  | null
+  | undefined
+  | Promise<Array<Number | null | undefined> | null | undefined>;
 
 export type Query_Custom_array_required_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Number[] | Promise<Number[]>;
+) =>
+  | Array<Number | null | undefined>
+  | Promise<Array<Number | null | undefined>>;
 
 export type Query_Custom_with_arg_Resolver = (
   parent: {},
@@ -359,21 +365,27 @@ export type Query_Scalar_nullable_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | Promise<boolean | null>;
+) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
 export type Query_Scalar_array_nullable_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean[] | null | Promise<boolean[] | null>;
+) =>
+  | Array<boolean | null | undefined>
+  | null
+  | undefined
+  | Promise<Array<boolean | null | undefined> | null | undefined>;
 
 export type Query_Scalar_array_required_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean[] | Promise<boolean[]>;
+) =>
+  | Array<boolean | null | undefined>
+  | Promise<Array<boolean | null | undefined>>;
 
 export type Query_Scalar_with_arg_Resolver = (
   parent: {},
@@ -409,21 +421,27 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number | null | Promise<Number | null>;
+  ) => Number | null | undefined | Promise<Number | null | undefined>;
 
   custom_array_nullable: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number[] | null | Promise<Number[] | null>;
+  ) =>
+    | Array<Number | null | undefined>
+    | null
+    | undefined
+    | Promise<Array<Number | null | undefined> | null | undefined>;
 
   custom_array_required: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number[] | Promise<Number[]>;
+  ) =>
+    | Array<Number | null | undefined>
+    | Promise<Array<Number | null | undefined>>;
 
   custom_with_arg: (
     parent: {},
@@ -451,21 +469,27 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   scalar_array_nullable: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean[] | null | Promise<boolean[] | null>;
+  ) =>
+    | Array<boolean | null | undefined>
+    | null
+    | undefined
+    | Promise<Array<boolean | null | undefined> | null | undefined>;
 
   scalar_array_required: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean[] | Promise<boolean[]>;
+  ) =>
+    | Array<boolean | null | undefined>
+    | Promise<Array<boolean | null | undefined>>;
 
   scalar_with_arg: (
     parent: {},
@@ -493,14 +517,14 @@ export type Number_Id_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | Promise<string | null>;
+) => string | null | undefined | Promise<string | null | undefined>;
 
 export type Number_Value_Resolver = (
   parent: Number,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | Promise<number | null>;
+) => number | null | undefined | Promise<number | null | undefined>;
 
 export interface Number_Resolvers {
   id: (
@@ -508,14 +532,14 @@ export interface Number_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   value: (
     parent: Number,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 }
 
 export interface Resolvers {
@@ -702,7 +726,7 @@ export type Professor_Degree_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | Promise<string | null>;
+) => string | null | undefined | Promise<string | null | undefined>;
 
 export interface Professor_Resolvers {
   degree: (
@@ -710,7 +734,7 @@ export interface Professor_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 }
 
 export interface Resolvers {
@@ -802,7 +826,7 @@ export type Query_CreateUser_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => User | null | Promise<User | null>;
+) => User | null | undefined | Promise<User | null | undefined>;
 
 export interface Query_Resolvers {
   createUser: (
@@ -810,7 +834,7 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => User | null | Promise<User | null>;
+  ) => User | null | undefined | Promise<User | null | undefined>;
 }
 
 // Types for User
@@ -935,21 +959,27 @@ export type Query_Custom_nullable_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => NumberNode | null | Promise<NumberNode | null>;
+) => NumberNode | null | undefined | Promise<NumberNode | null | undefined>;
 
 export type Query_Custom_array_nullable_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => NumberNode[] | null | Promise<NumberNode[] | null>;
+) =>
+  | Array<NumberNode | null | undefined>
+  | null
+  | undefined
+  | Promise<Array<NumberNode | null | undefined> | null | undefined>;
 
 export type Query_Custom_array_required_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => NumberNode[] | Promise<NumberNode[]>;
+) =>
+  | Array<NumberNode | null | undefined>
+  | Promise<Array<NumberNode | null | undefined>>;
 
 export type Query_Custom_with_arg_Resolver = (
   parent: {},
@@ -977,21 +1007,27 @@ export type Query_Scalar_nullable_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | Promise<boolean | null>;
+) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
 export type Query_Scalar_array_nullable_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean[] | null | Promise<boolean[] | null>;
+) =>
+  | Array<boolean | null | undefined>
+  | null
+  | undefined
+  | Promise<Array<boolean | null | undefined> | null | undefined>;
 
 export type Query_Scalar_array_required_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean[] | Promise<boolean[]>;
+) =>
+  | Array<boolean | null | undefined>
+  | Promise<Array<boolean | null | undefined>>;
 
 export type Query_Scalar_with_arg_Resolver = (
   parent: {},
@@ -1027,21 +1063,27 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => NumberNode | null | Promise<NumberNode | null>;
+  ) => NumberNode | null | undefined | Promise<NumberNode | null | undefined>;
 
   custom_array_nullable: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => NumberNode[] | null | Promise<NumberNode[] | null>;
+  ) =>
+    | Array<NumberNode | null | undefined>
+    | null
+    | undefined
+    | Promise<Array<NumberNode | null | undefined> | null | undefined>;
 
   custom_array_required: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => NumberNode[] | Promise<NumberNode[]>;
+  ) =>
+    | Array<NumberNode | null | undefined>
+    | Promise<Array<NumberNode | null | undefined>>;
 
   custom_with_arg: (
     parent: {},
@@ -1069,21 +1111,27 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   scalar_array_nullable: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean[] | null | Promise<boolean[] | null>;
+  ) =>
+    | Array<boolean | null | undefined>
+    | null
+    | undefined
+    | Promise<Array<boolean | null | undefined> | null | undefined>;
 
   scalar_array_required: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean[] | Promise<boolean[]>;
+  ) =>
+    | Array<boolean | null | undefined>
+    | Promise<Array<boolean | null | undefined>>;
 
   scalar_with_arg: (
     parent: {},
@@ -1111,14 +1159,14 @@ export type Number_Id_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | Promise<string | null>;
+) => string | null | undefined | Promise<string | null | undefined>;
 
 export type Number_Value_Resolver = (
   parent: NumberNode,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | Promise<number | null>;
+) => number | null | undefined | Promise<number | null | undefined>;
 
 export interface Number_Resolvers {
   id: (
@@ -1126,14 +1174,14 @@ export interface Number_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   value: (
     parent: NumberNode,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 }
 
 export interface Resolvers {
diff --git a/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap b/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
index 58d2d337..11acad8b 100644
--- a/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
+++ b/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
@@ -64,7 +64,7 @@ export interface Query_Args_HomesInPriceRange {
 }
 
 export interface Query_Args_ExperiencesByCity {
-  cities: string[];
+  cities: Array<string>;
 }
 
 export type Query_TopExperiences_Resolver = (
@@ -72,56 +72,56 @@ export type Query_TopExperiences_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Experience[] | Promise<Experience[]>;
+) => Array<Experience> | Promise<Array<Experience>>;
 
 export type Query_TopHomes_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Home[] | Promise<Home[]>;
+) => Array<Home> | Promise<Array<Home>>;
 
 export type Query_HomesInPriceRange_Resolver = (
   parent: {},
   args: Query_Args_HomesInPriceRange,
   ctx: Context,
   info: GraphQLResolveInfo
-) => Home[] | Promise<Home[]>;
+) => Array<Home> | Promise<Array<Home>>;
 
 export type Query_TopReservations_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Reservation[] | Promise<Reservation[]>;
+) => Array<Reservation> | Promise<Array<Reservation>>;
 
 export type Query_FeaturedDestinations_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Neighbourhood[] | Promise<Neighbourhood[]>;
+) => Array<Neighbourhood> | Promise<Array<Neighbourhood>>;
 
 export type Query_ExperiencesByCity_Resolver = (
   parent: {},
   args: Query_Args_ExperiencesByCity,
   ctx: Context,
   info: GraphQLResolveInfo
-) => ExperiencesByCity[] | Promise<ExperiencesByCity[]>;
+) => Array<ExperiencesByCity> | Promise<Array<ExperiencesByCity>>;
 
 export type Query_Viewer_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Viewer | null | Promise<Viewer | null>;
+) => Viewer | null | undefined | Promise<Viewer | null | undefined>;
 
 export type Query_MyLocation_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Location | null | Promise<Location | null>;
+) => Location | null | undefined | Promise<Location | null | undefined>;
 
 export interface Query_Resolvers {
   topExperiences: (
@@ -129,56 +129,56 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Experience[] | Promise<Experience[]>;
+  ) => Array<Experience> | Promise<Array<Experience>>;
 
   topHomes: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Home[] | Promise<Home[]>;
+  ) => Array<Home> | Promise<Array<Home>>;
 
   homesInPriceRange: (
     parent: {},
     args: Query_Args_HomesInPriceRange,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Home[] | Promise<Home[]>;
+  ) => Array<Home> | Promise<Array<Home>>;
 
   topReservations: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Reservation[] | Promise<Reservation[]>;
+  ) => Array<Reservation> | Promise<Array<Reservation>>;
 
   featuredDestinations: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Neighbourhood[] | Promise<Neighbourhood[]>;
+  ) => Array<Neighbourhood> | Promise<Array<Neighbourhood>>;
 
   experiencesByCity: (
     parent: {},
     args: Query_Args_ExperiencesByCity,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => ExperiencesByCity[] | Promise<ExperiencesByCity[]>;
+  ) => Array<ExperiencesByCity> | Promise<Array<ExperiencesByCity>>;
 
   viewer: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Viewer | null | Promise<Viewer | null>;
+  ) => Viewer | null | undefined | Promise<Viewer | null | undefined>;
 
   myLocation: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Location | null | Promise<Location | null>;
+  ) => Location | null | undefined | Promise<Location | null | undefined>;
 }
 
 // Types for Experience
@@ -206,7 +206,11 @@ export type Experience_Category_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => ExperienceCategory | null | Promise<ExperienceCategory | null>;
+) =>
+  | ExperienceCategory
+  | null
+  | undefined
+  | Promise<ExperienceCategory | null | undefined>;
 
 export type Experience_Title_Resolver = (
   parent: Experience,
@@ -234,7 +238,7 @@ export type Experience_Reviews_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Review[] | Promise<Review[]>;
+) => Array<Review> | Promise<Array<Review>>;
 
 export type Experience_Preview_Resolver = (
   parent: Experience,
@@ -263,7 +267,11 @@ export interface Experience_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => ExperienceCategory | null | Promise<ExperienceCategory | null>;
+  ) =>
+    | ExperienceCategory
+    | null
+    | undefined
+    | Promise<ExperienceCategory | null | undefined>;
 
   title: (
     parent: Experience,
@@ -291,7 +299,7 @@ export interface Experience_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Review[] | Promise<Review[]>;
+  ) => Array<Review> | Promise<Array<Review>>;
 
   preview: (
     parent: Experience,
@@ -343,7 +351,7 @@ export type ExperienceCategory_Experience_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Experience | null | Promise<Experience | null>;
+) => Experience | null | undefined | Promise<Experience | null | undefined>;
 
 export interface ExperienceCategory_Resolvers {
   id: (
@@ -372,7 +380,7 @@ export interface ExperienceCategory_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Experience | null | Promise<Experience | null>;
+  ) => Experience | null | undefined | Promise<Experience | null | undefined>;
 }
 
 // Types for Location
@@ -412,14 +420,14 @@ export type Location_Address_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | Promise<string | null>;
+) => string | null | undefined | Promise<string | null | undefined>;
 
 export type Location_Directions_Resolver = (
   parent: Location,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | Promise<string | null>;
+) => string | null | undefined | Promise<string | null | undefined>;
 
 export interface Location_Resolvers {
   id: (
@@ -448,14 +456,14 @@ export interface Location_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   directions: (
     parent: Location,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 }
 
 // Types for Review
@@ -663,7 +671,7 @@ export const Home_defaultResolvers = {
 };
 
 export interface Home_Args_Pictures {
-  first: number | null;
+  first: number | null | undefined;
 }
 
 export type Home_Id_Resolver = (
@@ -678,7 +686,7 @@ export type Home_Name_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | Promise<string | null>;
+) => string | null | undefined | Promise<string | null | undefined>;
 
 export type Home_Description_Resolver = (
   parent: Home,
@@ -699,14 +707,14 @@ export type Home_AvgRating_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | Promise<number | null>;
+) => number | null | undefined | Promise<number | null | undefined>;
 
 export type Home_Pictures_Resolver = (
   parent: Home,
   args: Home_Args_Pictures,
   ctx: Context,
   info: GraphQLResolveInfo
-) => Picture[] | Promise<Picture[]>;
+) => Array<Picture> | Promise<Array<Picture>>;
 
 export type Home_PerNight_Resolver = (
   parent: Home,
@@ -728,7 +736,7 @@ export interface Home_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   description: (
     parent: Home,
@@ -749,14 +757,14 @@ export interface Home_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   pictures: (
     parent: Home,
     args: Home_Args_Pictures,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture[] | Promise<Picture[]>;
+  ) => Array<Picture> | Promise<Array<Picture>>;
 
   perNight: (
     parent: Home,
@@ -804,7 +812,7 @@ export type Reservation_Pictures_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Picture[] | Promise<Picture[]>;
+) => Array<Picture> | Promise<Array<Picture>>;
 
 export type Reservation_Location_Resolver = (
   parent: Reservation,
@@ -861,7 +869,7 @@ export interface Reservation_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture[] | Promise<Picture[]>;
+  ) => Array<Picture> | Promise<Array<Picture>>;
 
   location: (
     parent: Reservation,
@@ -930,7 +938,7 @@ export type Neighbourhood_HomePreview_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Picture | null | Promise<Picture | null>;
+) => Picture | null | undefined | Promise<Picture | null | undefined>;
 
 export type Neighbourhood_City_Resolver = (
   parent: Neighbourhood,
@@ -980,7 +988,7 @@ export interface Neighbourhood_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture | null | Promise<Picture | null>;
+  ) => Picture | null | undefined | Promise<Picture | null | undefined>;
 
   city: (
     parent: Neighbourhood,
@@ -1051,7 +1059,7 @@ export type ExperiencesByCity_Experiences_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Experience[] | Promise<Experience[]>;
+) => Array<Experience> | Promise<Array<Experience>>;
 
 export type ExperiencesByCity_City_Resolver = (
   parent: ExperiencesByCity,
@@ -1066,7 +1074,7 @@ export interface ExperiencesByCity_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Experience[] | Promise<Experience[]>;
+  ) => Array<Experience> | Promise<Array<Experience>>;
 
   city: (
     parent: ExperiencesByCity,
@@ -1094,7 +1102,7 @@ export type Viewer_Bookings_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Booking[] | Promise<Booking[]>;
+) => Array<Booking> | Promise<Array<Booking>>;
 
 export interface Viewer_Resolvers {
   me: (
@@ -1109,7 +1117,7 @@ export interface Viewer_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Booking[] | Promise<Booking[]>;
+  ) => Array<Booking> | Promise<Array<Booking>>;
 }
 
 // Types for User
@@ -1141,7 +1149,11 @@ export type User_Bookings_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Booking[] | Promise<Booking[]>;
+) =>
+  | Array<Booking>
+  | null
+  | undefined
+  | Promise<Array<Booking> | null | undefined>;
 
 export type User_CreatedAt_Resolver = (
   parent: User,
@@ -1169,7 +1181,11 @@ export type User_HostingExperiences_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Experience[] | Promise<Experience[]>;
+) =>
+  | Array<Experience>
+  | null
+  | undefined
+  | Promise<Array<Experience> | null | undefined>;
 
 export type User_Id_Resolver = (
   parent: User,
@@ -1204,21 +1220,29 @@ export type User_Notifications_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Notification[] | Promise<Notification[]>;
+) =>
+  | Array<Notification>
+  | null
+  | undefined
+  | Promise<Array<Notification> | null | undefined>;
 
 export type User_OwnedPlaces_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Place[] | Promise<Place[]>;
+) => Array<Place> | null | undefined | Promise<Array<Place> | null | undefined>;
 
 export type User_PaymentAccount_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => PaymentAccount[] | Promise<PaymentAccount[]>;
+) =>
+  | Array<PaymentAccount>
+  | null
+  | undefined
+  | Promise<Array<PaymentAccount> | null | undefined>;
 
 export type User_Phone_Resolver = (
   parent: User,
@@ -1232,35 +1256,43 @@ export type User_ProfilePicture_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Picture | null | Promise<Picture | null>;
+) => Picture | null | undefined | Promise<Picture | null | undefined>;
 
 export type User_ReceivedMessages_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Message[] | Promise<Message[]>;
+) =>
+  | Array<Message>
+  | null
+  | undefined
+  | Promise<Array<Message> | null | undefined>;
 
 export type User_ResponseRate_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | Promise<number | null>;
+) => number | null | undefined | Promise<number | null | undefined>;
 
 export type User_ResponseTime_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | Promise<number | null>;
+) => number | null | undefined | Promise<number | null | undefined>;
 
 export type User_SentMessages_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Message[] | Promise<Message[]>;
+) =>
+  | Array<Message>
+  | null
+  | undefined
+  | Promise<Array<Message> | null | undefined>;
 
 export type User_UpdatedAt_Resolver = (
   parent: User,
@@ -1282,7 +1314,11 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Booking[] | Promise<Booking[]>;
+  ) =>
+    | Array<Booking>
+    | null
+    | undefined
+    | Promise<Array<Booking> | null | undefined>;
 
   createdAt: (
     parent: User,
@@ -1310,7 +1346,11 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Experience[] | Promise<Experience[]>;
+  ) =>
+    | Array<Experience>
+    | null
+    | undefined
+    | Promise<Array<Experience> | null | undefined>;
 
   id: (
     parent: User,
@@ -1345,21 +1385,33 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Notification[] | Promise<Notification[]>;
+  ) =>
+    | Array<Notification>
+    | null
+    | undefined
+    | Promise<Array<Notification> | null | undefined>;
 
   ownedPlaces: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Place[] | Promise<Place[]>;
+  ) =>
+    | Array<Place>
+    | null
+    | undefined
+    | Promise<Array<Place> | null | undefined>;
 
   paymentAccount: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PaymentAccount[] | Promise<PaymentAccount[]>;
+  ) =>
+    | Array<PaymentAccount>
+    | null
+    | undefined
+    | Promise<Array<PaymentAccount> | null | undefined>;
 
   phone: (
     parent: User,
@@ -1373,35 +1425,43 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture | null | Promise<Picture | null>;
+  ) => Picture | null | undefined | Promise<Picture | null | undefined>;
 
   receivedMessages: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Message[] | Promise<Message[]>;
+  ) =>
+    | Array<Message>
+    | null
+    | undefined
+    | Promise<Array<Message> | null | undefined>;
 
   responseRate: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   responseTime: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   sentMessages: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Message[] | Promise<Message[]>;
+  ) =>
+    | Array<Message>
+    | null
+    | undefined
+    | Promise<Array<Message> | null | undefined>;
 
   updatedAt: (
     parent: User,
@@ -1570,14 +1630,14 @@ export type Place_Name_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | Promise<string | null>;
+) => string | null | undefined | Promise<string | null | undefined>;
 
 export type Place_Size_Resolver = (
   parent: Place,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => PLACE_SIZES | null | Promise<PLACE_SIZES | null>;
+) => PLACE_SIZES | null | undefined | Promise<PLACE_SIZES | null | undefined>;
 
 export type Place_ShortDescription_Resolver = (
   parent: Place,
@@ -1633,7 +1693,7 @@ export type Place_Reviews_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Review[] | Promise<Review[]>;
+) => Array<Review> | Promise<Array<Review>>;
 
 export type Place_Amenities_Resolver = (
   parent: Place,
@@ -1675,35 +1735,43 @@ export type Place_GuestRequirements_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => GuestRequirements | null | Promise<GuestRequirements | null>;
+) =>
+  | GuestRequirements
+  | null
+  | undefined
+  | Promise<GuestRequirements | null | undefined>;
 
 export type Place_Policies_Resolver = (
   parent: Place,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Policies | null | Promise<Policies | null>;
+) => Policies | null | undefined | Promise<Policies | null | undefined>;
 
 export type Place_HouseRules_Resolver = (
   parent: Place,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => HouseRules | null | Promise<HouseRules | null>;
+) => HouseRules | null | undefined | Promise<HouseRules | null | undefined>;
 
 export type Place_Bookings_Resolver = (
   parent: Place,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Booking[] | Promise<Booking[]>;
+) => Array<Booking> | Promise<Array<Booking>>;
 
 export type Place_Pictures_Resolver = (
   parent: Place,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Picture[] | Promise<Picture[]>;
+) =>
+  | Array<Picture>
+  | null
+  | undefined
+  | Promise<Array<Picture> | null | undefined>;
 
 export type Place_Popularity_Resolver = (
   parent: Place,
@@ -1725,14 +1793,14 @@ export interface Place_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   size: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PLACE_SIZES | null | Promise<PLACE_SIZES | null>;
+  ) => PLACE_SIZES | null | undefined | Promise<PLACE_SIZES | null | undefined>;
 
   shortDescription: (
     parent: Place,
@@ -1788,7 +1856,7 @@ export interface Place_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Review[] | Promise<Review[]>;
+  ) => Array<Review> | Promise<Array<Review>>;
 
   amenities: (
     parent: Place,
@@ -1830,35 +1898,43 @@ export interface Place_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => GuestRequirements | null | Promise<GuestRequirements | null>;
+  ) =>
+    | GuestRequirements
+    | null
+    | undefined
+    | Promise<GuestRequirements | null | undefined>;
 
   policies: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Policies | null | Promise<Policies | null>;
+  ) => Policies | null | undefined | Promise<Policies | null | undefined>;
 
   houseRules: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => HouseRules | null | Promise<HouseRules | null>;
+  ) => HouseRules | null | undefined | Promise<HouseRules | null | undefined>;
 
   bookings: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Booking[] | Promise<Booking[]>;
+  ) => Array<Booking> | Promise<Array<Booking>>;
 
   pictures: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture[] | Promise<Picture[]>;
+  ) =>
+    | Array<Picture>
+    | null
+    | undefined
+    | Promise<Array<Picture> | null | undefined>;
 
   popularity: (
     parent: Place,
@@ -2541,21 +2617,21 @@ export type Pricing_CleaningFee_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | Promise<number | null>;
+) => number | null | undefined | Promise<number | null | undefined>;
 
 export type Pricing_Currency_Resolver = (
   parent: Pricing,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => CURRENCY | null | Promise<CURRENCY | null>;
+) => CURRENCY | null | undefined | Promise<CURRENCY | null | undefined>;
 
 export type Pricing_ExtraGuests_Resolver = (
   parent: Pricing,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | Promise<number | null>;
+) => number | null | undefined | Promise<number | null | undefined>;
 
 export type Pricing_Id_Resolver = (
   parent: Pricing,
@@ -2569,7 +2645,7 @@ export type Pricing_MonthlyDiscount_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | Promise<number | null>;
+) => number | null | undefined | Promise<number | null | undefined>;
 
 export type Pricing_PerNight_Resolver = (
   parent: Pricing,
@@ -2583,7 +2659,7 @@ export type Pricing_SecurityDeposit_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | Promise<number | null>;
+) => number | null | undefined | Promise<number | null | undefined>;
 
 export type Pricing_SmartPricing_Resolver = (
   parent: Pricing,
@@ -2597,14 +2673,14 @@ export type Pricing_WeekendPricing_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | Promise<number | null>;
+) => number | null | undefined | Promise<number | null | undefined>;
 
 export type Pricing_WeeklyDiscount_Resolver = (
   parent: Pricing,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | Promise<number | null>;
+) => number | null | undefined | Promise<number | null | undefined>;
 
 export interface Pricing_Resolvers {
   averageMonthly: (
@@ -2633,21 +2709,21 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   currency: (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => CURRENCY | null | Promise<CURRENCY | null>;
+  ) => CURRENCY | null | undefined | Promise<CURRENCY | null | undefined>;
 
   extraGuests: (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   id: (
     parent: Pricing,
@@ -2661,7 +2737,7 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   perNight: (
     parent: Pricing,
@@ -2675,7 +2751,7 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   smartPricing: (
     parent: Pricing,
@@ -2689,14 +2765,14 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   weeklyDiscount: (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 }
 
 // Types for PlaceViews
@@ -2927,7 +3003,7 @@ export type HouseRules_AdditionalRules_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | Promise<string | null>;
+) => string | null | undefined | Promise<string | null | undefined>;
 
 export type HouseRules_CreatedAt_Resolver = (
   parent: HouseRules,
@@ -2948,35 +3024,35 @@ export type HouseRules_PartiesAndEventsAllowed_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | Promise<boolean | null>;
+) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
 export type HouseRules_PetsAllowed_Resolver = (
   parent: HouseRules,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | Promise<boolean | null>;
+) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
 export type HouseRules_SmokingAllowed_Resolver = (
   parent: HouseRules,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | Promise<boolean | null>;
+) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
 export type HouseRules_SuitableForChildren_Resolver = (
   parent: HouseRules,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | Promise<boolean | null>;
+) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
 export type HouseRules_SuitableForInfants_Resolver = (
   parent: HouseRules,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | Promise<boolean | null>;
+) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
 export type HouseRules_UpdatedAt_Resolver = (
   parent: HouseRules,
@@ -2991,7 +3067,7 @@ export interface HouseRules_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   createdAt: (
     parent: HouseRules,
@@ -3012,35 +3088,35 @@ export interface HouseRules_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   petsAllowed: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   smokingAllowed: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   suitableForChildren: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   suitableForInfants: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   updatedAt: (
     parent: HouseRules,
@@ -3164,7 +3240,11 @@ export type PaymentAccount_Type_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => PAYMENT_PROVIDER | null | Promise<PAYMENT_PROVIDER | null>;
+) =>
+  | PAYMENT_PROVIDER
+  | null
+  | undefined
+  | Promise<PAYMENT_PROVIDER | null | undefined>;
 
 export type PaymentAccount_User_Resolver = (
   parent: PaymentAccount,
@@ -3178,21 +3258,29 @@ export type PaymentAccount_Payments_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Payment[] | Promise<Payment[]>;
+) => Array<Payment> | Promise<Array<Payment>>;
 
 export type PaymentAccount_Paypal_Resolver = (
   parent: PaymentAccount,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => PaypalInformation | null | Promise<PaypalInformation | null>;
+) =>
+  | PaypalInformation
+  | null
+  | undefined
+  | Promise<PaypalInformation | null | undefined>;
 
 export type PaymentAccount_Creditcard_Resolver = (
   parent: PaymentAccount,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => CreditCardInformation | null | Promise<CreditCardInformation | null>;
+) =>
+  | CreditCardInformation
+  | null
+  | undefined
+  | Promise<CreditCardInformation | null | undefined>;
 
 export interface PaymentAccount_Resolvers {
   id: (
@@ -3214,7 +3302,11 @@ export interface PaymentAccount_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PAYMENT_PROVIDER | null | Promise<PAYMENT_PROVIDER | null>;
+  ) =>
+    | PAYMENT_PROVIDER
+    | null
+    | undefined
+    | Promise<PAYMENT_PROVIDER | null | undefined>;
 
   user: (
     parent: PaymentAccount,
@@ -3228,21 +3320,29 @@ export interface PaymentAccount_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Payment[] | Promise<Payment[]>;
+  ) => Array<Payment> | Promise<Array<Payment>>;
 
   paypal: (
     parent: PaymentAccount,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PaypalInformation | null | Promise<PaypalInformation | null>;
+  ) =>
+    | PaypalInformation
+    | null
+    | undefined
+    | Promise<PaypalInformation | null | undefined>;
 
   creditcard: (
     parent: PaymentAccount,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => CreditCardInformation | null | Promise<CreditCardInformation | null>;
+  ) =>
+    | CreditCardInformation
+    | null
+    | undefined
+    | Promise<CreditCardInformation | null | undefined>;
 }
 
 // Types for PaypalInformation
@@ -3388,7 +3488,11 @@ export type CreditCardInformation_PaymentAccount_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => PaymentAccount | null | Promise<PaymentAccount | null>;
+) =>
+  | PaymentAccount
+  | null
+  | undefined
+  | Promise<PaymentAccount | null | undefined>;
 
 export type CreditCardInformation_PostalCode_Resolver = (
   parent: CreditCardInformation,
@@ -3466,7 +3570,11 @@ export interface CreditCardInformation_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PaymentAccount | null | Promise<PaymentAccount | null>;
+  ) =>
+    | PaymentAccount
+    | null
+    | undefined
+    | Promise<PaymentAccount | null | undefined>;
 
   postalCode: (
     parent: CreditCardInformation,
@@ -3527,7 +3635,11 @@ export type Notification_Type_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => NOTIFICATION_TYPE | null | Promise<NOTIFICATION_TYPE | null>;
+) =>
+  | NOTIFICATION_TYPE
+  | null
+  | undefined
+  | Promise<NOTIFICATION_TYPE | null | undefined>;
 
 export type Notification_User_Resolver = (
   parent: Notification,
@@ -3570,7 +3682,11 @@ export interface Notification_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => NOTIFICATION_TYPE | null | Promise<NOTIFICATION_TYPE | null>;
+  ) =>
+    | NOTIFICATION_TYPE
+    | null
+    | undefined
+    | Promise<NOTIFICATION_TYPE | null | undefined>;
 
   user: (
     parent: Notification,
diff --git a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
index b9d6ba47..3f4f187e 100644
--- a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
+++ b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
@@ -23,7 +23,7 @@ export namespace QueryResolvers {
     args: ArgsCreateUser,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => User | null | Promise<User | null>;
+  ) => User | null | undefined | Promise<User | null | undefined>;
 
   export interface Type {
     createUser: (
@@ -31,7 +31,7 @@ export namespace QueryResolvers {
       args: ArgsCreateUser,
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => User | null | Promise<User | null>;
+    ) => User | null | undefined | Promise<User | null | undefined>;
   }
 }
 
@@ -175,16 +175,16 @@ export namespace MutationResolvers {
 
   export interface AddMemberData {
     email: string;
-    projects: string[];
-    sideProjects: string[] | null;
+    projects: Array<string>;
+    sideProjects: Array<string | null | undefined> | null | undefined;
     profile: ProfileData | null;
-    phones: PhoneData[];
+    phones: Array<PhoneData | null | undefined>;
     isVIP: boolean;
   }
   export interface ProfileData {
-    firstName: string | null;
-    lastName: string | null;
-    photo: Photo | null;
+    firstName: string | null | undefined;
+    lastName: string | null | undefined;
+    photo: Photo | null | undefined;
   }
   export interface Photo {
     title: string;
@@ -201,7 +201,7 @@ export namespace MutationResolvers {
   }
 
   export interface ArgsAddMembers {
-    data: AddMemberData[];
+    data: Array<AddMemberData>;
   }
 
   export type AddMemberResolver = (
@@ -245,14 +245,14 @@ export namespace AddMemberPayloadResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   export type ExistingUserInviteSentResolver = (
     parent: AddMemberPayload,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   export interface Type {
     newUserId: (
@@ -260,14 +260,14 @@ export namespace AddMemberPayloadResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | Promise<string | null>;
+    ) => string | null | undefined | Promise<string | null | undefined>;
 
     existingUserInviteSent: (
       parent: AddMemberPayload,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | Promise<boolean | null>;
+    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
   }
 }
 
@@ -348,7 +348,7 @@ export namespace MutationResolvers {
 
   export interface AddMemberData {
     email: string;
-    projects: string[];
+    projects: Array<string>;
   }
 
   export interface ArgsAddMember {
@@ -382,7 +382,7 @@ export namespace AddMemberPayloadResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   export interface Type {
     json: (
@@ -390,7 +390,7 @@ export namespace AddMemberPayloadResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | Promise<string | null>;
+    ) => string | null | undefined | Promise<string | null | undefined>;
   }
 }
 
@@ -497,21 +497,27 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number | null | Promise<Number | null>;
+  ) => Number | null | undefined | Promise<Number | null | undefined>;
 
   export type Custom_array_nullableResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number[] | null | Promise<Number[] | null>;
+  ) =>
+    | Array<Number | null | undefined>
+    | null
+    | undefined
+    | Promise<Array<Number | null | undefined> | null | undefined>;
 
   export type Custom_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number[] | Promise<Number[]>;
+  ) =>
+    | Array<Number | null | undefined>
+    | Promise<Array<Number | null | undefined>>;
 
   export type Custom_with_argResolver = (
     parent: undefined,
@@ -539,21 +545,27 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   export type Scalar_array_nullableResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean[] | null | Promise<boolean[] | null>;
+  ) =>
+    | Array<boolean | null | undefined>
+    | null
+    | undefined
+    | Promise<Array<boolean | null | undefined> | null | undefined>;
 
   export type Scalar_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean[] | Promise<boolean[]>;
+  ) =>
+    | Array<boolean | null | undefined>
+    | Promise<Array<boolean | null | undefined>>;
 
   export type Scalar_with_argResolver = (
     parent: undefined,
@@ -589,21 +601,27 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Number | null | Promise<Number | null>;
+    ) => Number | null | undefined | Promise<Number | null | undefined>;
 
     custom_array_nullable: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Number[] | null | Promise<Number[] | null>;
+    ) =>
+      | Array<Number | null | undefined>
+      | null
+      | undefined
+      | Promise<Array<Number | null | undefined> | null | undefined>;
 
     custom_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Number[] | Promise<Number[]>;
+    ) =>
+      | Array<Number | null | undefined>
+      | Promise<Array<Number | null | undefined>>;
 
     custom_with_arg: (
       parent: undefined,
@@ -631,21 +649,27 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | Promise<boolean | null>;
+    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
     scalar_array_nullable: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean[] | null | Promise<boolean[] | null>;
+    ) =>
+      | Array<boolean | null | undefined>
+      | null
+      | undefined
+      | Promise<Array<boolean | null | undefined> | null | undefined>;
 
     scalar_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean[] | Promise<boolean[]>;
+    ) =>
+      | Array<boolean | null | undefined>
+      | Promise<Array<boolean | null | undefined>>;
 
     scalar_with_arg: (
       parent: undefined,
@@ -674,14 +698,14 @@ export namespace NumberResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   export type ValueResolver = (
     parent: Number,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export interface Type {
     id: (
@@ -689,14 +713,14 @@ export namespace NumberResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | Promise<string | null>;
+    ) => string | null | undefined | Promise<string | null | undefined>;
 
     value: (
       parent: Number,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
   }
 }
 
@@ -884,7 +908,7 @@ export namespace ProfessorResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   export interface Type {
     degree: (
@@ -892,7 +916,7 @@ export namespace ProfessorResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | Promise<string | null>;
+    ) => string | null | undefined | Promise<string | null | undefined>;
   }
 }
 
@@ -986,7 +1010,7 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => User | null | Promise<User | null>;
+  ) => User | null | undefined | Promise<User | null | undefined>;
 
   export interface Type {
     createUser: (
@@ -994,7 +1018,7 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => User | null | Promise<User | null>;
+    ) => User | null | undefined | Promise<User | null | undefined>;
   }
 }
 
@@ -1123,21 +1147,27 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => NumberNode | null | Promise<NumberNode | null>;
+  ) => NumberNode | null | undefined | Promise<NumberNode | null | undefined>;
 
   export type Custom_array_nullableResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => NumberNode[] | null | Promise<NumberNode[] | null>;
+  ) =>
+    | Array<NumberNode | null | undefined>
+    | null
+    | undefined
+    | Promise<Array<NumberNode | null | undefined> | null | undefined>;
 
   export type Custom_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => NumberNode[] | Promise<NumberNode[]>;
+  ) =>
+    | Array<NumberNode | null | undefined>
+    | Promise<Array<NumberNode | null | undefined>>;
 
   export type Custom_with_argResolver = (
     parent: undefined,
@@ -1165,21 +1195,27 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   export type Scalar_array_nullableResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean[] | null | Promise<boolean[] | null>;
+  ) =>
+    | Array<boolean | null | undefined>
+    | null
+    | undefined
+    | Promise<Array<boolean | null | undefined> | null | undefined>;
 
   export type Scalar_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean[] | Promise<boolean[]>;
+  ) =>
+    | Array<boolean | null | undefined>
+    | Promise<Array<boolean | null | undefined>>;
 
   export type Scalar_with_argResolver = (
     parent: undefined,
@@ -1215,21 +1251,27 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => NumberNode | null | Promise<NumberNode | null>;
+    ) => NumberNode | null | undefined | Promise<NumberNode | null | undefined>;
 
     custom_array_nullable: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => NumberNode[] | null | Promise<NumberNode[] | null>;
+    ) =>
+      | Array<NumberNode | null | undefined>
+      | null
+      | undefined
+      | Promise<Array<NumberNode | null | undefined> | null | undefined>;
 
     custom_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => NumberNode[] | Promise<NumberNode[]>;
+    ) =>
+      | Array<NumberNode | null | undefined>
+      | Promise<Array<NumberNode | null | undefined>>;
 
     custom_with_arg: (
       parent: undefined,
@@ -1257,21 +1299,27 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | Promise<boolean | null>;
+    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
     scalar_array_nullable: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean[] | null | Promise<boolean[] | null>;
+    ) =>
+      | Array<boolean | null | undefined>
+      | null
+      | undefined
+      | Promise<Array<boolean | null | undefined> | null | undefined>;
 
     scalar_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean[] | Promise<boolean[]>;
+    ) =>
+      | Array<boolean | null | undefined>
+      | Promise<Array<boolean | null | undefined>>;
 
     scalar_with_arg: (
       parent: undefined,
@@ -1300,14 +1348,14 @@ export namespace NumberResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   export type ValueResolver = (
     parent: NumberNode,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export interface Type {
     id: (
@@ -1315,14 +1363,14 @@ export namespace NumberResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | Promise<string | null>;
+    ) => string | null | undefined | Promise<string | null | undefined>;
 
     value: (
       parent: NumberNode,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
   }
 }
 
@@ -1465,21 +1513,27 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number | null | Promise<Number | null>;
+  ) => Number | null | undefined | Promise<Number | null | undefined>;
 
   export type Custom_array_nullableResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number[] | null | Promise<Number[] | null>;
+  ) =>
+    | Array<Number | null | undefined>
+    | null
+    | undefined
+    | Promise<Array<Number | null | undefined> | null | undefined>;
 
   export type Custom_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number[] | Promise<Number[]>;
+  ) =>
+    | Array<Number | null | undefined>
+    | Promise<Array<Number | null | undefined>>;
 
   export type Custom_with_argResolver = (
     parent: undefined,
@@ -1507,21 +1561,27 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   export type Scalar_array_nullableResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean[] | null | Promise<boolean[] | null>;
+  ) =>
+    | Array<boolean | null | undefined>
+    | null
+    | undefined
+    | Promise<Array<boolean | null | undefined> | null | undefined>;
 
   export type Scalar_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean[] | Promise<boolean[]>;
+  ) =>
+    | Array<boolean | null | undefined>
+    | Promise<Array<boolean | null | undefined>>;
 
   export type Scalar_with_argResolver = (
     parent: undefined,
@@ -1557,21 +1617,27 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Number | null | Promise<Number | null>;
+    ) => Number | null | undefined | Promise<Number | null | undefined>;
 
     custom_array_nullable: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Number[] | null | Promise<Number[] | null>;
+    ) =>
+      | Array<Number | null | undefined>
+      | null
+      | undefined
+      | Promise<Array<Number | null | undefined> | null | undefined>;
 
     custom_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Number[] | Promise<Number[]>;
+    ) =>
+      | Array<Number | null | undefined>
+      | Promise<Array<Number | null | undefined>>;
 
     custom_with_arg: (
       parent: undefined,
@@ -1599,21 +1665,27 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | Promise<boolean | null>;
+    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
     scalar_array_nullable: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean[] | null | Promise<boolean[] | null>;
+    ) =>
+      | Array<boolean | null | undefined>
+      | null
+      | undefined
+      | Promise<Array<boolean | null | undefined> | null | undefined>;
 
     scalar_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean[] | Promise<boolean[]>;
+    ) =>
+      | Array<boolean | null | undefined>
+      | Promise<Array<boolean | null | undefined>>;
 
     scalar_with_arg: (
       parent: undefined,
@@ -1642,14 +1714,14 @@ export namespace NumberResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   export type ValueResolver = (
     parent: Number,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export interface Type {
     id: (
@@ -1657,14 +1729,14 @@ export namespace NumberResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | Promise<string | null>;
+    ) => string | null | undefined | Promise<string | null | undefined>;
 
     value: (
       parent: Number,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
   }
 }
 
diff --git a/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap b/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
index a217cfa8..8189423a 100644
--- a/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
+++ b/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
@@ -63,7 +63,7 @@ export namespace QueryResolvers {
   }
 
   export interface ArgsExperiencesByCity {
-    cities: string[];
+    cities: Array<string>;
   }
 
   export type TopExperiencesResolver = (
@@ -71,56 +71,56 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Experience[] | Promise<Experience[]>;
+  ) => Array<Experience> | Promise<Array<Experience>>;
 
   export type TopHomesResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Home[] | Promise<Home[]>;
+  ) => Array<Home> | Promise<Array<Home>>;
 
   export type HomesInPriceRangeResolver = (
     parent: undefined,
     args: ArgsHomesInPriceRange,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Home[] | Promise<Home[]>;
+  ) => Array<Home> | Promise<Array<Home>>;
 
   export type TopReservationsResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Reservation[] | Promise<Reservation[]>;
+  ) => Array<Reservation> | Promise<Array<Reservation>>;
 
   export type FeaturedDestinationsResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Neighbourhood[] | Promise<Neighbourhood[]>;
+  ) => Array<Neighbourhood> | Promise<Array<Neighbourhood>>;
 
   export type ExperiencesByCityResolver = (
     parent: undefined,
     args: ArgsExperiencesByCity,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => ExperiencesByCity[] | Promise<ExperiencesByCity[]>;
+  ) => Array<ExperiencesByCity> | Promise<Array<ExperiencesByCity>>;
 
   export type ViewerResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Viewer | null | Promise<Viewer | null>;
+  ) => Viewer | null | undefined | Promise<Viewer | null | undefined>;
 
   export type MyLocationResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Location | null | Promise<Location | null>;
+  ) => Location | null | undefined | Promise<Location | null | undefined>;
 
   export interface Type {
     topExperiences: (
@@ -128,56 +128,56 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Experience[] | Promise<Experience[]>;
+    ) => Array<Experience> | Promise<Array<Experience>>;
 
     topHomes: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Home[] | Promise<Home[]>;
+    ) => Array<Home> | Promise<Array<Home>>;
 
     homesInPriceRange: (
       parent: undefined,
       args: ArgsHomesInPriceRange,
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Home[] | Promise<Home[]>;
+    ) => Array<Home> | Promise<Array<Home>>;
 
     topReservations: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Reservation[] | Promise<Reservation[]>;
+    ) => Array<Reservation> | Promise<Array<Reservation>>;
 
     featuredDestinations: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Neighbourhood[] | Promise<Neighbourhood[]>;
+    ) => Array<Neighbourhood> | Promise<Array<Neighbourhood>>;
 
     experiencesByCity: (
       parent: undefined,
       args: ArgsExperiencesByCity,
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => ExperiencesByCity[] | Promise<ExperiencesByCity[]>;
+    ) => Array<ExperiencesByCity> | Promise<Array<ExperiencesByCity>>;
 
     viewer: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Viewer | null | Promise<Viewer | null>;
+    ) => Viewer | null | undefined | Promise<Viewer | null | undefined>;
 
     myLocation: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Location | null | Promise<Location | null>;
+    ) => Location | null | undefined | Promise<Location | null | undefined>;
   }
 }
 
@@ -206,7 +206,11 @@ export namespace ExperienceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => ExperienceCategory | null | Promise<ExperienceCategory | null>;
+  ) =>
+    | ExperienceCategory
+    | null
+    | undefined
+    | Promise<ExperienceCategory | null | undefined>;
 
   export type TitleResolver = (
     parent: Experience,
@@ -234,7 +238,7 @@ export namespace ExperienceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Review[] | Promise<Review[]>;
+  ) => Array<Review> | Promise<Array<Review>>;
 
   export type PreviewResolver = (
     parent: Experience,
@@ -263,7 +267,11 @@ export namespace ExperienceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => ExperienceCategory | null | Promise<ExperienceCategory | null>;
+    ) =>
+      | ExperienceCategory
+      | null
+      | undefined
+      | Promise<ExperienceCategory | null | undefined>;
 
     title: (
       parent: Experience,
@@ -291,7 +299,7 @@ export namespace ExperienceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Review[] | Promise<Review[]>;
+    ) => Array<Review> | Promise<Array<Review>>;
 
     preview: (
       parent: Experience,
@@ -344,7 +352,7 @@ export namespace ExperienceCategoryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Experience | null | Promise<Experience | null>;
+  ) => Experience | null | undefined | Promise<Experience | null | undefined>;
 
   export interface Type {
     id: (
@@ -373,7 +381,7 @@ export namespace ExperienceCategoryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Experience | null | Promise<Experience | null>;
+    ) => Experience | null | undefined | Promise<Experience | null | undefined>;
   }
 }
 
@@ -414,14 +422,14 @@ export namespace LocationResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   export type DirectionsResolver = (
     parent: Location,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   export interface Type {
     id: (
@@ -450,14 +458,14 @@ export namespace LocationResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | Promise<string | null>;
+    ) => string | null | undefined | Promise<string | null | undefined>;
 
     directions: (
       parent: Location,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | Promise<string | null>;
+    ) => string | null | undefined | Promise<string | null | undefined>;
   }
 }
 
@@ -668,7 +676,7 @@ export namespace HomeResolvers {
   };
 
   export interface ArgsPictures {
-    first: number | null;
+    first: number | null | undefined;
   }
 
   export type IdResolver = (
@@ -683,7 +691,7 @@ export namespace HomeResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   export type DescriptionResolver = (
     parent: Home,
@@ -704,14 +712,14 @@ export namespace HomeResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export type PicturesResolver = (
     parent: Home,
     args: ArgsPictures,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture[] | Promise<Picture[]>;
+  ) => Array<Picture> | Promise<Array<Picture>>;
 
   export type PerNightResolver = (
     parent: Home,
@@ -733,7 +741,7 @@ export namespace HomeResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | Promise<string | null>;
+    ) => string | null | undefined | Promise<string | null | undefined>;
 
     description: (
       parent: Home,
@@ -754,14 +762,14 @@ export namespace HomeResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
 
     pictures: (
       parent: Home,
       args: ArgsPictures,
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Picture[] | Promise<Picture[]>;
+    ) => Array<Picture> | Promise<Array<Picture>>;
 
     perNight: (
       parent: Home,
@@ -810,7 +818,7 @@ export namespace ReservationResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture[] | Promise<Picture[]>;
+  ) => Array<Picture> | Promise<Array<Picture>>;
 
   export type LocationResolver = (
     parent: Reservation,
@@ -867,7 +875,7 @@ export namespace ReservationResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Picture[] | Promise<Picture[]>;
+    ) => Array<Picture> | Promise<Array<Picture>>;
 
     location: (
       parent: Reservation,
@@ -937,7 +945,7 @@ export namespace NeighbourhoodResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture | null | Promise<Picture | null>;
+  ) => Picture | null | undefined | Promise<Picture | null | undefined>;
 
   export type CityResolver = (
     parent: Neighbourhood,
@@ -987,7 +995,7 @@ export namespace NeighbourhoodResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Picture | null | Promise<Picture | null>;
+    ) => Picture | null | undefined | Promise<Picture | null | undefined>;
 
     city: (
       parent: Neighbourhood,
@@ -1060,7 +1068,7 @@ export namespace ExperiencesByCityResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Experience[] | Promise<Experience[]>;
+  ) => Array<Experience> | Promise<Array<Experience>>;
 
   export type CityResolver = (
     parent: ExperiencesByCity,
@@ -1075,7 +1083,7 @@ export namespace ExperiencesByCityResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Experience[] | Promise<Experience[]>;
+    ) => Array<Experience> | Promise<Array<Experience>>;
 
     city: (
       parent: ExperiencesByCity,
@@ -1104,7 +1112,7 @@ export namespace ViewerResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Booking[] | Promise<Booking[]>;
+  ) => Array<Booking> | Promise<Array<Booking>>;
 
   export interface Type {
     me: (
@@ -1119,7 +1127,7 @@ export namespace ViewerResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Booking[] | Promise<Booking[]>;
+    ) => Array<Booking> | Promise<Array<Booking>>;
   }
 }
 
@@ -1152,7 +1160,11 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Booking[] | Promise<Booking[]>;
+  ) =>
+    | Array<Booking>
+    | null
+    | undefined
+    | Promise<Array<Booking> | null | undefined>;
 
   export type CreatedAtResolver = (
     parent: User,
@@ -1180,7 +1192,11 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Experience[] | Promise<Experience[]>;
+  ) =>
+    | Array<Experience>
+    | null
+    | undefined
+    | Promise<Array<Experience> | null | undefined>;
 
   export type IdResolver = (
     parent: User,
@@ -1215,21 +1231,33 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Notification[] | Promise<Notification[]>;
+  ) =>
+    | Array<Notification>
+    | null
+    | undefined
+    | Promise<Array<Notification> | null | undefined>;
 
   export type OwnedPlacesResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Place[] | Promise<Place[]>;
+  ) =>
+    | Array<Place>
+    | null
+    | undefined
+    | Promise<Array<Place> | null | undefined>;
 
   export type PaymentAccountResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PaymentAccount[] | Promise<PaymentAccount[]>;
+  ) =>
+    | Array<PaymentAccount>
+    | null
+    | undefined
+    | Promise<Array<PaymentAccount> | null | undefined>;
 
   export type PhoneResolver = (
     parent: User,
@@ -1243,35 +1271,43 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture | null | Promise<Picture | null>;
+  ) => Picture | null | undefined | Promise<Picture | null | undefined>;
 
   export type ReceivedMessagesResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Message[] | Promise<Message[]>;
+  ) =>
+    | Array<Message>
+    | null
+    | undefined
+    | Promise<Array<Message> | null | undefined>;
 
   export type ResponseRateResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export type ResponseTimeResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export type SentMessagesResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Message[] | Promise<Message[]>;
+  ) =>
+    | Array<Message>
+    | null
+    | undefined
+    | Promise<Array<Message> | null | undefined>;
 
   export type UpdatedAtResolver = (
     parent: User,
@@ -1293,7 +1329,11 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Booking[] | Promise<Booking[]>;
+    ) =>
+      | Array<Booking>
+      | null
+      | undefined
+      | Promise<Array<Booking> | null | undefined>;
 
     createdAt: (
       parent: User,
@@ -1321,7 +1361,11 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Experience[] | Promise<Experience[]>;
+    ) =>
+      | Array<Experience>
+      | null
+      | undefined
+      | Promise<Array<Experience> | null | undefined>;
 
     id: (
       parent: User,
@@ -1356,21 +1400,33 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Notification[] | Promise<Notification[]>;
+    ) =>
+      | Array<Notification>
+      | null
+      | undefined
+      | Promise<Array<Notification> | null | undefined>;
 
     ownedPlaces: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Place[] | Promise<Place[]>;
+    ) =>
+      | Array<Place>
+      | null
+      | undefined
+      | Promise<Array<Place> | null | undefined>;
 
     paymentAccount: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => PaymentAccount[] | Promise<PaymentAccount[]>;
+    ) =>
+      | Array<PaymentAccount>
+      | null
+      | undefined
+      | Promise<Array<PaymentAccount> | null | undefined>;
 
     phone: (
       parent: User,
@@ -1384,35 +1440,43 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Picture | null | Promise<Picture | null>;
+    ) => Picture | null | undefined | Promise<Picture | null | undefined>;
 
     receivedMessages: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Message[] | Promise<Message[]>;
+    ) =>
+      | Array<Message>
+      | null
+      | undefined
+      | Promise<Array<Message> | null | undefined>;
 
     responseRate: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
 
     responseTime: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
 
     sentMessages: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Message[] | Promise<Message[]>;
+    ) =>
+      | Array<Message>
+      | null
+      | undefined
+      | Promise<Array<Message> | null | undefined>;
 
     updatedAt: (
       parent: User,
@@ -1583,14 +1647,14 @@ export namespace PlaceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   export type SizeResolver = (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PLACE_SIZES | null | Promise<PLACE_SIZES | null>;
+  ) => PLACE_SIZES | null | undefined | Promise<PLACE_SIZES | null | undefined>;
 
   export type ShortDescriptionResolver = (
     parent: Place,
@@ -1646,7 +1710,7 @@ export namespace PlaceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Review[] | Promise<Review[]>;
+  ) => Array<Review> | Promise<Array<Review>>;
 
   export type AmenitiesResolver = (
     parent: Place,
@@ -1688,35 +1752,43 @@ export namespace PlaceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => GuestRequirements | null | Promise<GuestRequirements | null>;
+  ) =>
+    | GuestRequirements
+    | null
+    | undefined
+    | Promise<GuestRequirements | null | undefined>;
 
   export type PoliciesResolver = (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Policies | null | Promise<Policies | null>;
+  ) => Policies | null | undefined | Promise<Policies | null | undefined>;
 
   export type HouseRulesResolver = (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => HouseRules | null | Promise<HouseRules | null>;
+  ) => HouseRules | null | undefined | Promise<HouseRules | null | undefined>;
 
   export type BookingsResolver = (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Booking[] | Promise<Booking[]>;
+  ) => Array<Booking> | Promise<Array<Booking>>;
 
   export type PicturesResolver = (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture[] | Promise<Picture[]>;
+  ) =>
+    | Array<Picture>
+    | null
+    | undefined
+    | Promise<Array<Picture> | null | undefined>;
 
   export type PopularityResolver = (
     parent: Place,
@@ -1738,14 +1810,18 @@ export namespace PlaceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | Promise<string | null>;
+    ) => string | null | undefined | Promise<string | null | undefined>;
 
     size: (
       parent: Place,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => PLACE_SIZES | null | Promise<PLACE_SIZES | null>;
+    ) =>
+      | PLACE_SIZES
+      | null
+      | undefined
+      | Promise<PLACE_SIZES | null | undefined>;
 
     shortDescription: (
       parent: Place,
@@ -1801,7 +1877,7 @@ export namespace PlaceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Review[] | Promise<Review[]>;
+    ) => Array<Review> | Promise<Array<Review>>;
 
     amenities: (
       parent: Place,
@@ -1843,35 +1919,43 @@ export namespace PlaceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => GuestRequirements | null | Promise<GuestRequirements | null>;
+    ) =>
+      | GuestRequirements
+      | null
+      | undefined
+      | Promise<GuestRequirements | null | undefined>;
 
     policies: (
       parent: Place,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Policies | null | Promise<Policies | null>;
+    ) => Policies | null | undefined | Promise<Policies | null | undefined>;
 
     houseRules: (
       parent: Place,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => HouseRules | null | Promise<HouseRules | null>;
+    ) => HouseRules | null | undefined | Promise<HouseRules | null | undefined>;
 
     bookings: (
       parent: Place,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Booking[] | Promise<Booking[]>;
+    ) => Array<Booking> | Promise<Array<Booking>>;
 
     pictures: (
       parent: Place,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Picture[] | Promise<Picture[]>;
+    ) =>
+      | Array<Picture>
+      | null
+      | undefined
+      | Promise<Array<Picture> | null | undefined>;
 
     popularity: (
       parent: Place,
@@ -2558,21 +2642,21 @@ export namespace PricingResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export type CurrencyResolver = (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => CURRENCY | null | Promise<CURRENCY | null>;
+  ) => CURRENCY | null | undefined | Promise<CURRENCY | null | undefined>;
 
   export type ExtraGuestsResolver = (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export type IdResolver = (
     parent: Pricing,
@@ -2586,7 +2670,7 @@ export namespace PricingResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export type PerNightResolver = (
     parent: Pricing,
@@ -2600,7 +2684,7 @@ export namespace PricingResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export type SmartPricingResolver = (
     parent: Pricing,
@@ -2614,14 +2698,14 @@ export namespace PricingResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export type WeeklyDiscountResolver = (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | Promise<number | null>;
+  ) => number | null | undefined | Promise<number | null | undefined>;
 
   export interface Type {
     averageMonthly: (
@@ -2650,21 +2734,21 @@ export namespace PricingResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
 
     currency: (
       parent: Pricing,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => CURRENCY | null | Promise<CURRENCY | null>;
+    ) => CURRENCY | null | undefined | Promise<CURRENCY | null | undefined>;
 
     extraGuests: (
       parent: Pricing,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
 
     id: (
       parent: Pricing,
@@ -2678,7 +2762,7 @@ export namespace PricingResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
 
     perNight: (
       parent: Pricing,
@@ -2692,7 +2776,7 @@ export namespace PricingResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
 
     smartPricing: (
       parent: Pricing,
@@ -2706,14 +2790,14 @@ export namespace PricingResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
 
     weeklyDiscount: (
       parent: Pricing,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | Promise<number | null>;
+    ) => number | null | undefined | Promise<number | null | undefined>;
   }
 }
 
@@ -2950,7 +3034,7 @@ export namespace HouseRulesResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | Promise<string | null>;
+  ) => string | null | undefined | Promise<string | null | undefined>;
 
   export type CreatedAtResolver = (
     parent: HouseRules,
@@ -2971,35 +3055,35 @@ export namespace HouseRulesResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   export type PetsAllowedResolver = (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   export type SmokingAllowedResolver = (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   export type SuitableForChildrenResolver = (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   export type SuitableForInfantsResolver = (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | Promise<boolean | null>;
+  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
   export type UpdatedAtResolver = (
     parent: HouseRules,
@@ -3014,7 +3098,7 @@ export namespace HouseRulesResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | Promise<string | null>;
+    ) => string | null | undefined | Promise<string | null | undefined>;
 
     createdAt: (
       parent: HouseRules,
@@ -3035,35 +3119,35 @@ export namespace HouseRulesResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | Promise<boolean | null>;
+    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
     petsAllowed: (
       parent: HouseRules,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | Promise<boolean | null>;
+    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
     smokingAllowed: (
       parent: HouseRules,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | Promise<boolean | null>;
+    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
     suitableForChildren: (
       parent: HouseRules,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | Promise<boolean | null>;
+    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
     suitableForInfants: (
       parent: HouseRules,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | Promise<boolean | null>;
+    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
 
     updatedAt: (
       parent: HouseRules,
@@ -3189,7 +3273,11 @@ export namespace PaymentAccountResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PAYMENT_PROVIDER | null | Promise<PAYMENT_PROVIDER | null>;
+  ) =>
+    | PAYMENT_PROVIDER
+    | null
+    | undefined
+    | Promise<PAYMENT_PROVIDER | null | undefined>;
 
   export type UserResolver = (
     parent: PaymentAccount,
@@ -3203,21 +3291,29 @@ export namespace PaymentAccountResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Payment[] | Promise<Payment[]>;
+  ) => Array<Payment> | Promise<Array<Payment>>;
 
   export type PaypalResolver = (
     parent: PaymentAccount,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PaypalInformation | null | Promise<PaypalInformation | null>;
+  ) =>
+    | PaypalInformation
+    | null
+    | undefined
+    | Promise<PaypalInformation | null | undefined>;
 
   export type CreditcardResolver = (
     parent: PaymentAccount,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => CreditCardInformation | null | Promise<CreditCardInformation | null>;
+  ) =>
+    | CreditCardInformation
+    | null
+    | undefined
+    | Promise<CreditCardInformation | null | undefined>;
 
   export interface Type {
     id: (
@@ -3239,7 +3335,11 @@ export namespace PaymentAccountResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => PAYMENT_PROVIDER | null | Promise<PAYMENT_PROVIDER | null>;
+    ) =>
+      | PAYMENT_PROVIDER
+      | null
+      | undefined
+      | Promise<PAYMENT_PROVIDER | null | undefined>;
 
     user: (
       parent: PaymentAccount,
@@ -3253,21 +3353,29 @@ export namespace PaymentAccountResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Payment[] | Promise<Payment[]>;
+    ) => Array<Payment> | Promise<Array<Payment>>;
 
     paypal: (
       parent: PaymentAccount,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => PaypalInformation | null | Promise<PaypalInformation | null>;
+    ) =>
+      | PaypalInformation
+      | null
+      | undefined
+      | Promise<PaypalInformation | null | undefined>;
 
     creditcard: (
       parent: PaymentAccount,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => CreditCardInformation | null | Promise<CreditCardInformation | null>;
+    ) =>
+      | CreditCardInformation
+      | null
+      | undefined
+      | Promise<CreditCardInformation | null | undefined>;
   }
 }
 
@@ -3415,7 +3523,11 @@ export namespace CreditCardInformationResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PaymentAccount | null | Promise<PaymentAccount | null>;
+  ) =>
+    | PaymentAccount
+    | null
+    | undefined
+    | Promise<PaymentAccount | null | undefined>;
 
   export type PostalCodeResolver = (
     parent: CreditCardInformation,
@@ -3493,7 +3605,11 @@ export namespace CreditCardInformationResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => PaymentAccount | null | Promise<PaymentAccount | null>;
+    ) =>
+      | PaymentAccount
+      | null
+      | undefined
+      | Promise<PaymentAccount | null | undefined>;
 
     postalCode: (
       parent: CreditCardInformation,
@@ -3555,7 +3671,11 @@ export namespace NotificationResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => NOTIFICATION_TYPE | null | Promise<NOTIFICATION_TYPE | null>;
+  ) =>
+    | NOTIFICATION_TYPE
+    | null
+    | undefined
+    | Promise<NOTIFICATION_TYPE | null | undefined>;
 
   export type UserResolver = (
     parent: Notification,
@@ -3598,7 +3718,11 @@ export namespace NotificationResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => NOTIFICATION_TYPE | null | Promise<NOTIFICATION_TYPE | null>;
+    ) =>
+      | NOTIFICATION_TYPE
+      | null
+      | undefined
+      | Promise<NOTIFICATION_TYPE | null | undefined>;
 
     user: (
       parent: Notification,

From 5db2c8685e9555136c6469208afd933c108cf8c9 Mon Sep 17 00:00:00 2001
From: Jason Kuhrt <jasonkuhrt@me.com>
Date: Wed, 2 Jan 2019 21:27:43 -0500
Subject: [PATCH 2/8] chore: formatting

---
 packages/graphqlgen/src/generators/common.ts |  3 +++
 packages/graphqlgen/src/source-helper.ts     | 14 ++++++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/packages/graphqlgen/src/generators/common.ts b/packages/graphqlgen/src/generators/common.ts
index 9ab32353..6d084f49 100644
--- a/packages/graphqlgen/src/generators/common.ts
+++ b/packages/graphqlgen/src/generators/common.ts
@@ -201,6 +201,7 @@ export function printFieldLikeType(
   const isRequired = field.type.isArray
     ? field.type.isArrayRequired
     : field.type.isRequired
+
   const suffix = isRequired
     ? ''
     : field.defaultValue === null
@@ -208,9 +209,11 @@ export function printFieldLikeType(
     : field.defaultValue === undefined
     ? ' | null | undefined'
     : ''
+
   const type = field.type.isArray
     ? name + (field.type.isRequired ? '' : ' | null | undefined')
     : name + suffix
+
   return field.type.isArray ? `Array<${type}>${suffix}` : type
 }
 
diff --git a/packages/graphqlgen/src/source-helper.ts b/packages/graphqlgen/src/source-helper.ts
index bf953606..e383f663 100644
--- a/packages/graphqlgen/src/source-helper.ts
+++ b/packages/graphqlgen/src/source-helper.ts
@@ -132,7 +132,12 @@ function extractTypeDefinition(
 
 const getFinalType = (
   type: GraphQLInputType | GraphQLOutputType,
-  acc: FinalType = { isArray: false, isArrayRequired: false, isRequired: false, type },
+  acc: FinalType = {
+    isArray: false,
+    isArrayRequired: false,
+    isRequired: false,
+    type,
+  },
 ): FinalType => {
   if (type instanceof GraphQLNonNull) {
     acc.isRequired = true
@@ -161,7 +166,12 @@ function extractTypeLike(
   type: GraphQLInputType | GraphQLOutputType,
 ): GraphQLType {
   const typeLike: GraphQLType = {} as GraphQLType
-  const { isArray, isArrayRequired, isRequired, type: finalType } = getFinalType(type)
+  const {
+    isArray,
+    isArrayRequired,
+    isRequired,
+    type: finalType,
+  } = getFinalType(type)
   if (isRequired) {
     typeLike.isRequired = true
   }

From 5316bbee54e8be87c995ab3455754f4f9da48633 Mon Sep 17 00:00:00 2001
From: Jason Kuhrt <jasonkuhrt@me.com>
Date: Wed, 2 Jan 2019 22:12:07 -0500
Subject: [PATCH 3/8] feat: do not allow undefined in resolver return types

---
 .../graphqlgen/src/generators/common.spec.ts  |   5 +
 packages/graphqlgen/src/generators/common.ts  |  58 ++++
 .../src/generators/flow-generator.ts          |  12 +-
 .../graphqlgen/src/generators/ts-generator.ts |   4 +-
 .../flow/__snapshots__/basic.test.ts.snap     | 128 ++++----
 .../__snapshots__/large-schema.test.ts.snap   | 274 ++++++------------
 .../__snapshots__/basic.test.ts.snap          |  95 ++----
 .../__snapshots__/large-schema.test.ts.snap   | 146 +++-------
 8 files changed, 291 insertions(+), 431 deletions(-)

diff --git a/packages/graphqlgen/src/generators/common.spec.ts b/packages/graphqlgen/src/generators/common.spec.ts
index 03ccadcc..7935b95e 100644
--- a/packages/graphqlgen/src/generators/common.spec.ts
+++ b/packages/graphqlgen/src/generators/common.spec.ts
@@ -41,6 +41,7 @@ it('getDistinctInputTypes', () => {
             isUnion: false,
             isRequired: false,
             isArray: false,
+            isArrayRequired: false,
           },
         },
         {
@@ -56,6 +57,7 @@ it('getDistinctInputTypes', () => {
             isUnion: false,
             isRequired: false,
             isArray: false,
+            isArrayRequired: false,
           },
         },
       ],
@@ -85,6 +87,7 @@ it('getDistinctInputTypes', () => {
             isUnion: false,
             isRequired: false,
             isArray: false,
+            isArrayRequired: false,
           },
         },
       ],
@@ -114,6 +117,7 @@ it('getDistinctInputTypes', () => {
             isUnion: false,
             isRequired: false,
             isArray: false,
+            isArrayRequired: false,
           },
         },
       ],
@@ -143,6 +147,7 @@ it('getDistinctInputTypes', () => {
             isUnion: false,
             isRequired: false,
             isArray: false,
+            isArrayRequired: false,
           },
         },
       ],
diff --git a/packages/graphqlgen/src/generators/common.ts b/packages/graphqlgen/src/generators/common.ts
index 6d084f49..bf781ac4 100644
--- a/packages/graphqlgen/src/generators/common.ts
+++ b/packages/graphqlgen/src/generators/common.ts
@@ -217,6 +217,64 @@ export function printFieldLikeType(
   return field.type.isArray ? `Array<${type}>${suffix}` : type
 }
 
+export function printFieldLikeFlowType(
+  field: GraphQLTypeField,
+  modelMap: ModelMap,
+) {
+  const name = field.type.isScalar
+    ? getTypeFromGraphQLType(field.type.name)
+    : field.type.isInput || field.type.isEnum
+    ? field.type.name
+    : getModelName(field.type, modelMap)
+
+  const isRequired = field.type.isArray
+    ? field.type.isArrayRequired
+    : field.type.isRequired
+
+  const suffix = isRequired
+    ? ''
+    : field.defaultValue === null
+    ? ' | null'
+    : field.defaultValue === undefined
+    ? ' | null | void'
+    : ''
+
+  const type = field.type.isArray
+    ? name + (field.type.isRequired ? '' : ' | null | void')
+    : name + suffix
+
+  return field.type.isArray ? `Array<${type}>${suffix}` : type
+}
+
+export function printFieldLikeReturnType(
+  field: GraphQLTypeField,
+  modelMap: ModelMap,
+) {
+  const name = field.type.isScalar
+    ? getTypeFromGraphQLType(field.type.name)
+    : field.type.isInput || field.type.isEnum
+    ? field.type.name
+    : getModelName(field.type, modelMap)
+
+  const isRequired = field.type.isArray
+    ? field.type.isArrayRequired
+    : field.type.isRequired
+
+  const suffix = isRequired
+    ? ''
+    : field.defaultValue === null
+    ? ' | null'
+    : field.defaultValue === undefined
+    ? ' | null'
+    : ''
+
+  const type = field.type.isArray
+    ? name + (field.type.isRequired ? '' : ' | null')
+    : name + suffix
+
+  return field.type.isArray ? `Array<${type}>${suffix}` : type
+}
+
 export function getTypeFromGraphQLType(
   type: string,
 ): SpecificGraphQLScalarType {
diff --git a/packages/graphqlgen/src/generators/flow-generator.ts b/packages/graphqlgen/src/generators/flow-generator.ts
index 3c733b7c..6226c8e0 100644
--- a/packages/graphqlgen/src/generators/flow-generator.ts
+++ b/packages/graphqlgen/src/generators/flow-generator.ts
@@ -14,7 +14,8 @@ import {
   getModelName,
   groupModelsNameByImportPath,
   InputTypesMap,
-  printFieldLikeType,
+  printFieldLikeFlowType,
+  printFieldLikeReturnType,
   renderDefaultResolvers,
   renderEnums,
   TypeToInputTypeAssociation,
@@ -171,7 +172,7 @@ function renderInputTypeInterfaces(
         inputTypesMap[typeAssociation].name,
       )} {
       ${inputTypesMap[typeAssociation].fields.map(
-        field => `${field.name}: ${printFieldLikeType(field, modelMap)}`,
+        field => `${field.name}: ${printFieldLikeFlowType(field, modelMap)}`,
       )}
     }`
     })
@@ -201,7 +202,7 @@ function renderInputArgInterface(
     ${field.arguments
       .map(
         arg =>
-          `${arg.name}: ${getArgTypePrefix(type, arg)}${printFieldLikeType(
+          `${arg.name}: ${getArgTypePrefix(type, arg)}${printFieldLikeFlowType(
             arg as GraphQLTypeField,
             modelMap,
           )}`,
@@ -254,7 +255,8 @@ function renderResolverFunctionInterface(
     info: GraphQLResolveInfo,
   )
   `
-  const returnType = printFieldLikeType(field, modelMap)
+
+  const returnType = printFieldLikeReturnType(field, modelMap)
 
   if (type.name === 'Subscription') {
     return `
@@ -299,7 +301,7 @@ function renderResolverTypeInterfaceFunction(
     ctx: ${getContextName(context)},
     info: GraphQLResolveInfo,
   )`
-  const returnType = printFieldLikeType(field, modelMap)
+  const returnType = printFieldLikeFlowType(field, modelMap)
 
   if (type.name === 'Subscription') {
     return `
diff --git a/packages/graphqlgen/src/generators/ts-generator.ts b/packages/graphqlgen/src/generators/ts-generator.ts
index 02ff90b7..0fa3f2f3 100644
--- a/packages/graphqlgen/src/generators/ts-generator.ts
+++ b/packages/graphqlgen/src/generators/ts-generator.ts
@@ -10,6 +10,7 @@ import {
   TypeToInputTypeAssociation,
   InputTypesMap,
   printFieldLikeType,
+  printFieldLikeReturnType,
   getDistinctInputTypes,
   renderEnums,
   groupModelsNameByImportPath,
@@ -263,7 +264,8 @@ function renderResolverFunctionInterface(
     info: GraphQLResolveInfo,
   )
   `
-  const returnType = printFieldLikeType(field, modelMap)
+
+  const returnType = printFieldLikeReturnType(field, modelMap)
 
   if (type.name === 'Subscription') {
     return `
diff --git a/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap b/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
index a462ac6a..fba90ebf 100644
--- a/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
+++ b/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
@@ -24,7 +24,7 @@ export type Query_CreateUser_Resolver = (
   args: Query_Args_CreateUser,
   ctx: Context,
   info: GraphQLResolveInfo
-) => User | null | undefined | Promise<User | null | undefined>;
+) => User | null | Promise<User | null>;
 
 export interface Query_Resolvers {
   createUser: (
@@ -32,7 +32,7 @@ export interface Query_Resolvers {
     args: Query_Args_CreateUser,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => User | null | undefined | Promise<User | null | undefined>;
+  ) => User | null | void | Promise<User | null | void>;
 }
 
 // Types for User
@@ -205,7 +205,7 @@ export type AddMemberPayload_Json_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | undefined | Promise<string | null | undefined>;
+) => string | null | Promise<string | null>;
 
 export interface AddMemberPayload_Resolvers {
   json: (
@@ -213,7 +213,7 @@ export interface AddMemberPayload_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | void | Promise<string | null | void>;
 }
 
 export interface Resolvers {
@@ -317,27 +317,21 @@ export type Query_Custom_nullable_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Number | null | undefined | Promise<Number | null | undefined>;
+) => Number | null | Promise<Number | null>;
 
 export type Query_Custom_array_nullable_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<Number | null | undefined>
-  | null
-  | undefined
-  | Promise<Array<Number | null | undefined> | null | undefined>;
+) => Array<Number | null> | null | Promise<Array<Number | null> | null>;
 
 export type Query_Custom_array_required_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<Number | null | undefined>
-  | Promise<Array<Number | null | undefined>>;
+) => Array<Number | null> | Promise<Array<Number | null>>;
 
 export type Query_Custom_with_arg_Resolver = (
   parent: {},
@@ -365,27 +359,21 @@ export type Query_Scalar_nullable_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | undefined | Promise<boolean | null | undefined>;
+) => boolean | null | Promise<boolean | null>;
 
 export type Query_Scalar_array_nullable_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<boolean | null | undefined>
-  | null
-  | undefined
-  | Promise<Array<boolean | null | undefined> | null | undefined>;
+) => Array<boolean | null> | null | Promise<Array<boolean | null> | null>;
 
 export type Query_Scalar_array_required_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<boolean | null | undefined>
-  | Promise<Array<boolean | null | undefined>>;
+) => Array<boolean | null> | Promise<Array<boolean | null>>;
 
 export type Query_Scalar_with_arg_Resolver = (
   parent: {},
@@ -421,7 +409,7 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number | null | undefined | Promise<Number | null | undefined>;
+  ) => Number | null | void | Promise<Number | null | void>;
 
   custom_array_nullable: (
     parent: {},
@@ -429,19 +417,17 @@ export interface Query_Resolvers {
     ctx: Context,
     info: GraphQLResolveInfo
   ) =>
-    | Array<Number | null | undefined>
+    | Array<Number | null | void>
     | null
-    | undefined
-    | Promise<Array<Number | null | undefined> | null | undefined>;
+    | void
+    | Promise<Array<Number | null | void> | null | void>;
 
   custom_array_required: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Number | null | undefined>
-    | Promise<Array<Number | null | undefined>>;
+  ) => Array<Number | null | void> | Promise<Array<Number | null | void>>;
 
   custom_with_arg: (
     parent: {},
@@ -469,7 +455,7 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | void | Promise<boolean | null | void>;
 
   scalar_array_nullable: (
     parent: {},
@@ -477,19 +463,17 @@ export interface Query_Resolvers {
     ctx: Context,
     info: GraphQLResolveInfo
   ) =>
-    | Array<boolean | null | undefined>
+    | Array<boolean | null | void>
     | null
-    | undefined
-    | Promise<Array<boolean | null | undefined> | null | undefined>;
+    | void
+    | Promise<Array<boolean | null | void> | null | void>;
 
   scalar_array_required: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<boolean | null | undefined>
-    | Promise<Array<boolean | null | undefined>>;
+  ) => Array<boolean | null | void> | Promise<Array<boolean | null | void>>;
 
   scalar_with_arg: (
     parent: {},
@@ -517,14 +501,14 @@ export type Number_Id_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | undefined | Promise<string | null | undefined>;
+) => string | null | Promise<string | null>;
 
 export type Number_Value_Resolver = (
   parent: Number,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | undefined | Promise<number | null | undefined>;
+) => number | null | Promise<number | null>;
 
 export interface Number_Resolvers {
   id: (
@@ -532,14 +516,14 @@ export interface Number_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | void | Promise<string | null | void>;
 
   value: (
     parent: Number,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | void | Promise<number | null | void>;
 }
 
 export interface Resolvers {
@@ -722,7 +706,7 @@ export type Professor_Degree_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | undefined | Promise<string | null | undefined>;
+) => string | null | Promise<string | null>;
 
 export interface Professor_Resolvers {
   degree: (
@@ -730,7 +714,7 @@ export interface Professor_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | void | Promise<string | null | void>;
 }
 
 export interface Resolvers {
@@ -822,7 +806,7 @@ export type Query_CreateUser_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => User | null | undefined | Promise<User | null | undefined>;
+) => User | null | Promise<User | null>;
 
 export interface Query_Resolvers {
   createUser: (
@@ -830,7 +814,7 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => User | null | undefined | Promise<User | null | undefined>;
+  ) => User | null | void | Promise<User | null | void>;
 }
 
 // Types for User
@@ -955,27 +939,21 @@ export type Query_Custom_nullable_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => NumberNode | null | undefined | Promise<NumberNode | null | undefined>;
+) => NumberNode | null | Promise<NumberNode | null>;
 
 export type Query_Custom_array_nullable_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<NumberNode | null | undefined>
-  | null
-  | undefined
-  | Promise<Array<NumberNode | null | undefined> | null | undefined>;
+) => Array<NumberNode | null> | null | Promise<Array<NumberNode | null> | null>;
 
 export type Query_Custom_array_required_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<NumberNode | null | undefined>
-  | Promise<Array<NumberNode | null | undefined>>;
+) => Array<NumberNode | null> | Promise<Array<NumberNode | null>>;
 
 export type Query_Custom_with_arg_Resolver = (
   parent: {},
@@ -1003,27 +981,21 @@ export type Query_Scalar_nullable_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | undefined | Promise<boolean | null | undefined>;
+) => boolean | null | Promise<boolean | null>;
 
 export type Query_Scalar_array_nullable_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<boolean | null | undefined>
-  | null
-  | undefined
-  | Promise<Array<boolean | null | undefined> | null | undefined>;
+) => Array<boolean | null> | null | Promise<Array<boolean | null> | null>;
 
 export type Query_Scalar_array_required_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<boolean | null | undefined>
-  | Promise<Array<boolean | null | undefined>>;
+) => Array<boolean | null> | Promise<Array<boolean | null>>;
 
 export type Query_Scalar_with_arg_Resolver = (
   parent: {},
@@ -1059,7 +1031,7 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => NumberNode | null | undefined | Promise<NumberNode | null | undefined>;
+  ) => NumberNode | null | void | Promise<NumberNode | null | void>;
 
   custom_array_nullable: (
     parent: {},
@@ -1067,10 +1039,10 @@ export interface Query_Resolvers {
     ctx: Context,
     info: GraphQLResolveInfo
   ) =>
-    | Array<NumberNode | null | undefined>
+    | Array<NumberNode | null | void>
     | null
-    | undefined
-    | Promise<Array<NumberNode | null | undefined> | null | undefined>;
+    | void
+    | Promise<Array<NumberNode | null | void> | null | void>;
 
   custom_array_required: (
     parent: {},
@@ -1078,8 +1050,8 @@ export interface Query_Resolvers {
     ctx: Context,
     info: GraphQLResolveInfo
   ) =>
-    | Array<NumberNode | null | undefined>
-    | Promise<Array<NumberNode | null | undefined>>;
+    | Array<NumberNode | null | void>
+    | Promise<Array<NumberNode | null | void>>;
 
   custom_with_arg: (
     parent: {},
@@ -1107,7 +1079,7 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | void | Promise<boolean | null | void>;
 
   scalar_array_nullable: (
     parent: {},
@@ -1115,19 +1087,17 @@ export interface Query_Resolvers {
     ctx: Context,
     info: GraphQLResolveInfo
   ) =>
-    | Array<boolean | null | undefined>
+    | Array<boolean | null | void>
     | null
-    | undefined
-    | Promise<Array<boolean | null | undefined> | null | undefined>;
+    | void
+    | Promise<Array<boolean | null | void> | null | void>;
 
   scalar_array_required: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<boolean | null | undefined>
-    | Promise<Array<boolean | null | undefined>>;
+  ) => Array<boolean | null | void> | Promise<Array<boolean | null | void>>;
 
   scalar_with_arg: (
     parent: {},
@@ -1155,14 +1125,14 @@ export type Number_Id_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | undefined | Promise<string | null | undefined>;
+) => string | null | Promise<string | null>;
 
 export type Number_Value_Resolver = (
   parent: NumberNode,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | undefined | Promise<number | null | undefined>;
+) => number | null | Promise<number | null>;
 
 export interface Number_Resolvers {
   id: (
@@ -1170,14 +1140,14 @@ export interface Number_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | void | Promise<string | null | void>;
 
   value: (
     parent: NumberNode,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | void | Promise<number | null | void>;
 }
 
 export interface Resolvers {
diff --git a/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap b/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
index 16657ca1..ca8e370d 100644
--- a/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
+++ b/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
@@ -114,14 +114,14 @@ export type Query_Viewer_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Viewer | null | undefined | Promise<Viewer | null | undefined>;
+) => Viewer | null | Promise<Viewer | null>;
 
 export type Query_MyLocation_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Location | null | undefined | Promise<Location | null | undefined>;
+) => Location | null | Promise<Location | null>;
 
 export interface Query_Resolvers {
   topExperiences: (
@@ -171,14 +171,14 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Viewer | null | undefined | Promise<Viewer | null | undefined>;
+  ) => Viewer | null | void | Promise<Viewer | null | void>;
 
   myLocation: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Location | null | undefined | Promise<Location | null | undefined>;
+  ) => Location | null | void | Promise<Location | null | void>;
 }
 
 // Types for Experience
@@ -206,11 +206,7 @@ export type Experience_Category_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | ExperienceCategory
-  | null
-  | undefined
-  | Promise<ExperienceCategory | null | undefined>;
+) => ExperienceCategory | null | Promise<ExperienceCategory | null>;
 
 export type Experience_Title_Resolver = (
   parent: Experience,
@@ -270,8 +266,8 @@ export interface Experience_Resolvers {
   ) =>
     | ExperienceCategory
     | null
-    | undefined
-    | Promise<ExperienceCategory | null | undefined>;
+    | void
+    | Promise<ExperienceCategory | null | void>;
 
   title: (
     parent: Experience,
@@ -351,7 +347,7 @@ export type ExperienceCategory_Experience_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Experience | null | undefined | Promise<Experience | null | undefined>;
+) => Experience | null | Promise<Experience | null>;
 
 export interface ExperienceCategory_Resolvers {
   id: (
@@ -380,7 +376,7 @@ export interface ExperienceCategory_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Experience | null | undefined | Promise<Experience | null | undefined>;
+  ) => Experience | null | void | Promise<Experience | null | void>;
 }
 
 // Types for Location
@@ -420,14 +416,14 @@ export type Location_Address_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | undefined | Promise<string | null | undefined>;
+) => string | null | Promise<string | null>;
 
 export type Location_Directions_Resolver = (
   parent: Location,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | undefined | Promise<string | null | undefined>;
+) => string | null | Promise<string | null>;
 
 export interface Location_Resolvers {
   id: (
@@ -456,14 +452,14 @@ export interface Location_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | void | Promise<string | null | void>;
 
   directions: (
     parent: Location,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | void | Promise<string | null | void>;
 }
 
 // Types for Review
@@ -671,7 +667,7 @@ export const Home_defaultResolvers = {
 };
 
 export interface Home_Args_Pictures {
-  first: number | null | undefined;
+  first: number | null | void;
 }
 
 export type Home_Id_Resolver = (
@@ -686,7 +682,7 @@ export type Home_Name_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | undefined | Promise<string | null | undefined>;
+) => string | null | Promise<string | null>;
 
 export type Home_Description_Resolver = (
   parent: Home,
@@ -707,7 +703,7 @@ export type Home_AvgRating_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | undefined | Promise<number | null | undefined>;
+) => number | null | Promise<number | null>;
 
 export type Home_Pictures_Resolver = (
   parent: Home,
@@ -736,7 +732,7 @@ export interface Home_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | void | Promise<string | null | void>;
 
   description: (
     parent: Home,
@@ -757,7 +753,7 @@ export interface Home_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | void | Promise<number | null | void>;
 
   pictures: (
     parent: Home,
@@ -938,7 +934,7 @@ export type Neighbourhood_HomePreview_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Picture | null | undefined | Promise<Picture | null | undefined>;
+) => Picture | null | Promise<Picture | null>;
 
 export type Neighbourhood_City_Resolver = (
   parent: Neighbourhood,
@@ -988,7 +984,7 @@ export interface Neighbourhood_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture | null | undefined | Promise<Picture | null | undefined>;
+  ) => Picture | null | void | Promise<Picture | null | void>;
 
   city: (
     parent: Neighbourhood,
@@ -1149,11 +1145,7 @@ export type User_Bookings_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<Booking>
-  | null
-  | undefined
-  | Promise<Array<Booking> | null | undefined>;
+) => Array<Booking> | null | Promise<Array<Booking> | null>;
 
 export type User_CreatedAt_Resolver = (
   parent: User,
@@ -1181,11 +1173,7 @@ export type User_HostingExperiences_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<Experience>
-  | null
-  | undefined
-  | Promise<Array<Experience> | null | undefined>;
+) => Array<Experience> | null | Promise<Array<Experience> | null>;
 
 export type User_Id_Resolver = (
   parent: User,
@@ -1220,29 +1208,21 @@ export type User_Notifications_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<Notification>
-  | null
-  | undefined
-  | Promise<Array<Notification> | null | undefined>;
+) => Array<Notification> | null | Promise<Array<Notification> | null>;
 
 export type User_OwnedPlaces_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Place> | null | undefined | Promise<Array<Place> | null | undefined>;
+) => Array<Place> | null | Promise<Array<Place> | null>;
 
 export type User_PaymentAccount_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<PaymentAccount>
-  | null
-  | undefined
-  | Promise<Array<PaymentAccount> | null | undefined>;
+) => Array<PaymentAccount> | null | Promise<Array<PaymentAccount> | null>;
 
 export type User_Phone_Resolver = (
   parent: User,
@@ -1256,43 +1236,35 @@ export type User_ProfilePicture_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Picture | null | undefined | Promise<Picture | null | undefined>;
+) => Picture | null | Promise<Picture | null>;
 
 export type User_ReceivedMessages_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<Message>
-  | null
-  | undefined
-  | Promise<Array<Message> | null | undefined>;
+) => Array<Message> | null | Promise<Array<Message> | null>;
 
 export type User_ResponseRate_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | undefined | Promise<number | null | undefined>;
+) => number | null | Promise<number | null>;
 
 export type User_ResponseTime_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | undefined | Promise<number | null | undefined>;
+) => number | null | Promise<number | null>;
 
 export type User_SentMessages_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<Message>
-  | null
-  | undefined
-  | Promise<Array<Message> | null | undefined>;
+) => Array<Message> | null | Promise<Array<Message> | null>;
 
 export type User_UpdatedAt_Resolver = (
   parent: User,
@@ -1314,11 +1286,7 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Booking>
-    | null
-    | undefined
-    | Promise<Array<Booking> | null | undefined>;
+  ) => Array<Booking> | null | void | Promise<Array<Booking> | null | void>;
 
   createdAt: (
     parent: User,
@@ -1349,8 +1317,8 @@ export interface User_Resolvers {
   ) =>
     | Array<Experience>
     | null
-    | undefined
-    | Promise<Array<Experience> | null | undefined>;
+    | void
+    | Promise<Array<Experience> | null | void>;
 
   id: (
     parent: User,
@@ -1388,19 +1356,15 @@ export interface User_Resolvers {
   ) =>
     | Array<Notification>
     | null
-    | undefined
-    | Promise<Array<Notification> | null | undefined>;
+    | void
+    | Promise<Array<Notification> | null | void>;
 
   ownedPlaces: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Place>
-    | null
-    | undefined
-    | Promise<Array<Place> | null | undefined>;
+  ) => Array<Place> | null | void | Promise<Array<Place> | null | void>;
 
   paymentAccount: (
     parent: User,
@@ -1410,8 +1374,8 @@ export interface User_Resolvers {
   ) =>
     | Array<PaymentAccount>
     | null
-    | undefined
-    | Promise<Array<PaymentAccount> | null | undefined>;
+    | void
+    | Promise<Array<PaymentAccount> | null | void>;
 
   phone: (
     parent: User,
@@ -1425,43 +1389,35 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture | null | undefined | Promise<Picture | null | undefined>;
+  ) => Picture | null | void | Promise<Picture | null | void>;
 
   receivedMessages: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Message>
-    | null
-    | undefined
-    | Promise<Array<Message> | null | undefined>;
+  ) => Array<Message> | null | void | Promise<Array<Message> | null | void>;
 
   responseRate: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | void | Promise<number | null | void>;
 
   responseTime: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | void | Promise<number | null | void>;
 
   sentMessages: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Message>
-    | null
-    | undefined
-    | Promise<Array<Message> | null | undefined>;
+  ) => Array<Message> | null | void | Promise<Array<Message> | null | void>;
 
   updatedAt: (
     parent: User,
@@ -1630,14 +1586,14 @@ export type Place_Name_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | undefined | Promise<string | null | undefined>;
+) => string | null | Promise<string | null>;
 
 export type Place_Size_Resolver = (
   parent: Place,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => PLACE_SIZES | null | undefined | Promise<PLACE_SIZES | null | undefined>;
+) => PLACE_SIZES | null | Promise<PLACE_SIZES | null>;
 
 export type Place_ShortDescription_Resolver = (
   parent: Place,
@@ -1735,25 +1691,21 @@ export type Place_GuestRequirements_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | GuestRequirements
-  | null
-  | undefined
-  | Promise<GuestRequirements | null | undefined>;
+) => GuestRequirements | null | Promise<GuestRequirements | null>;
 
 export type Place_Policies_Resolver = (
   parent: Place,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Policies | null | undefined | Promise<Policies | null | undefined>;
+) => Policies | null | Promise<Policies | null>;
 
 export type Place_HouseRules_Resolver = (
   parent: Place,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => HouseRules | null | undefined | Promise<HouseRules | null | undefined>;
+) => HouseRules | null | Promise<HouseRules | null>;
 
 export type Place_Bookings_Resolver = (
   parent: Place,
@@ -1767,11 +1719,7 @@ export type Place_Pictures_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | Array<Picture>
-  | null
-  | undefined
-  | Promise<Array<Picture> | null | undefined>;
+) => Array<Picture> | null | Promise<Array<Picture> | null>;
 
 export type Place_Popularity_Resolver = (
   parent: Place,
@@ -1793,14 +1741,14 @@ export interface Place_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | void | Promise<string | null | void>;
 
   size: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PLACE_SIZES | null | undefined | Promise<PLACE_SIZES | null | undefined>;
+  ) => PLACE_SIZES | null | void | Promise<PLACE_SIZES | null | void>;
 
   shortDescription: (
     parent: Place,
@@ -1901,22 +1849,22 @@ export interface Place_Resolvers {
   ) =>
     | GuestRequirements
     | null
-    | undefined
-    | Promise<GuestRequirements | null | undefined>;
+    | void
+    | Promise<GuestRequirements | null | void>;
 
   policies: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Policies | null | undefined | Promise<Policies | null | undefined>;
+  ) => Policies | null | void | Promise<Policies | null | void>;
 
   houseRules: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => HouseRules | null | undefined | Promise<HouseRules | null | undefined>;
+  ) => HouseRules | null | void | Promise<HouseRules | null | void>;
 
   bookings: (
     parent: Place,
@@ -1930,11 +1878,7 @@ export interface Place_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Picture>
-    | null
-    | undefined
-    | Promise<Array<Picture> | null | undefined>;
+  ) => Array<Picture> | null | void | Promise<Array<Picture> | null | void>;
 
   popularity: (
     parent: Place,
@@ -2617,21 +2561,21 @@ export type Pricing_CleaningFee_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | undefined | Promise<number | null | undefined>;
+) => number | null | Promise<number | null>;
 
 export type Pricing_Currency_Resolver = (
   parent: Pricing,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => CURRENCY | null | undefined | Promise<CURRENCY | null | undefined>;
+) => CURRENCY | null | Promise<CURRENCY | null>;
 
 export type Pricing_ExtraGuests_Resolver = (
   parent: Pricing,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | undefined | Promise<number | null | undefined>;
+) => number | null | Promise<number | null>;
 
 export type Pricing_Id_Resolver = (
   parent: Pricing,
@@ -2645,7 +2589,7 @@ export type Pricing_MonthlyDiscount_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | undefined | Promise<number | null | undefined>;
+) => number | null | Promise<number | null>;
 
 export type Pricing_PerNight_Resolver = (
   parent: Pricing,
@@ -2659,7 +2603,7 @@ export type Pricing_SecurityDeposit_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | undefined | Promise<number | null | undefined>;
+) => number | null | Promise<number | null>;
 
 export type Pricing_SmartPricing_Resolver = (
   parent: Pricing,
@@ -2673,14 +2617,14 @@ export type Pricing_WeekendPricing_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | undefined | Promise<number | null | undefined>;
+) => number | null | Promise<number | null>;
 
 export type Pricing_WeeklyDiscount_Resolver = (
   parent: Pricing,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => number | null | undefined | Promise<number | null | undefined>;
+) => number | null | Promise<number | null>;
 
 export interface Pricing_Resolvers {
   averageMonthly: (
@@ -2709,21 +2653,21 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | void | Promise<number | null | void>;
 
   currency: (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => CURRENCY | null | undefined | Promise<CURRENCY | null | undefined>;
+  ) => CURRENCY | null | void | Promise<CURRENCY | null | void>;
 
   extraGuests: (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | void | Promise<number | null | void>;
 
   id: (
     parent: Pricing,
@@ -2737,7 +2681,7 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | void | Promise<number | null | void>;
 
   perNight: (
     parent: Pricing,
@@ -2751,7 +2695,7 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | void | Promise<number | null | void>;
 
   smartPricing: (
     parent: Pricing,
@@ -2765,14 +2709,14 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | void | Promise<number | null | void>;
 
   weeklyDiscount: (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | void | Promise<number | null | void>;
 }
 
 // Types for PlaceViews
@@ -3003,7 +2947,7 @@ export type HouseRules_AdditionalRules_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => string | null | undefined | Promise<string | null | undefined>;
+) => string | null | Promise<string | null>;
 
 export type HouseRules_CreatedAt_Resolver = (
   parent: HouseRules,
@@ -3024,35 +2968,35 @@ export type HouseRules_PartiesAndEventsAllowed_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | undefined | Promise<boolean | null | undefined>;
+) => boolean | null | Promise<boolean | null>;
 
 export type HouseRules_PetsAllowed_Resolver = (
   parent: HouseRules,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | undefined | Promise<boolean | null | undefined>;
+) => boolean | null | Promise<boolean | null>;
 
 export type HouseRules_SmokingAllowed_Resolver = (
   parent: HouseRules,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | undefined | Promise<boolean | null | undefined>;
+) => boolean | null | Promise<boolean | null>;
 
 export type HouseRules_SuitableForChildren_Resolver = (
   parent: HouseRules,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | undefined | Promise<boolean | null | undefined>;
+) => boolean | null | Promise<boolean | null>;
 
 export type HouseRules_SuitableForInfants_Resolver = (
   parent: HouseRules,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => boolean | null | undefined | Promise<boolean | null | undefined>;
+) => boolean | null | Promise<boolean | null>;
 
 export type HouseRules_UpdatedAt_Resolver = (
   parent: HouseRules,
@@ -3067,7 +3011,7 @@ export interface HouseRules_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | void | Promise<string | null | void>;
 
   createdAt: (
     parent: HouseRules,
@@ -3088,35 +3032,35 @@ export interface HouseRules_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | void | Promise<boolean | null | void>;
 
   petsAllowed: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | void | Promise<boolean | null | void>;
 
   smokingAllowed: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | void | Promise<boolean | null | void>;
 
   suitableForChildren: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | void | Promise<boolean | null | void>;
 
   suitableForInfants: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | void | Promise<boolean | null | void>;
 
   updatedAt: (
     parent: HouseRules,
@@ -3240,11 +3184,7 @@ export type PaymentAccount_Type_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | PAYMENT_PROVIDER
-  | null
-  | undefined
-  | Promise<PAYMENT_PROVIDER | null | undefined>;
+) => PAYMENT_PROVIDER | null | Promise<PAYMENT_PROVIDER | null>;
 
 export type PaymentAccount_User_Resolver = (
   parent: PaymentAccount,
@@ -3265,22 +3205,14 @@ export type PaymentAccount_Paypal_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | PaypalInformation
-  | null
-  | undefined
-  | Promise<PaypalInformation | null | undefined>;
+) => PaypalInformation | null | Promise<PaypalInformation | null>;
 
 export type PaymentAccount_Creditcard_Resolver = (
   parent: PaymentAccount,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | CreditCardInformation
-  | null
-  | undefined
-  | Promise<CreditCardInformation | null | undefined>;
+) => CreditCardInformation | null | Promise<CreditCardInformation | null>;
 
 export interface PaymentAccount_Resolvers {
   id: (
@@ -3302,11 +3234,7 @@ export interface PaymentAccount_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | PAYMENT_PROVIDER
-    | null
-    | undefined
-    | Promise<PAYMENT_PROVIDER | null | undefined>;
+  ) => PAYMENT_PROVIDER | null | void | Promise<PAYMENT_PROVIDER | null | void>;
 
   user: (
     parent: PaymentAccount,
@@ -3330,8 +3258,8 @@ export interface PaymentAccount_Resolvers {
   ) =>
     | PaypalInformation
     | null
-    | undefined
-    | Promise<PaypalInformation | null | undefined>;
+    | void
+    | Promise<PaypalInformation | null | void>;
 
   creditcard: (
     parent: PaymentAccount,
@@ -3341,8 +3269,8 @@ export interface PaymentAccount_Resolvers {
   ) =>
     | CreditCardInformation
     | null
-    | undefined
-    | Promise<CreditCardInformation | null | undefined>;
+    | void
+    | Promise<CreditCardInformation | null | void>;
 }
 
 // Types for PaypalInformation
@@ -3488,11 +3416,7 @@ export type CreditCardInformation_PaymentAccount_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | PaymentAccount
-  | null
-  | undefined
-  | Promise<PaymentAccount | null | undefined>;
+) => PaymentAccount | null | Promise<PaymentAccount | null>;
 
 export type CreditCardInformation_PostalCode_Resolver = (
   parent: CreditCardInformation,
@@ -3570,11 +3494,7 @@ export interface CreditCardInformation_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | PaymentAccount
-    | null
-    | undefined
-    | Promise<PaymentAccount | null | undefined>;
+  ) => PaymentAccount | null | void | Promise<PaymentAccount | null | void>;
 
   postalCode: (
     parent: CreditCardInformation,
@@ -3635,11 +3555,7 @@ export type Notification_Type_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) =>
-  | NOTIFICATION_TYPE
-  | null
-  | undefined
-  | Promise<NOTIFICATION_TYPE | null | undefined>;
+) => NOTIFICATION_TYPE | null | Promise<NOTIFICATION_TYPE | null>;
 
 export type Notification_User_Resolver = (
   parent: Notification,
@@ -3685,8 +3601,8 @@ export interface Notification_Resolvers {
   ) =>
     | NOTIFICATION_TYPE
     | null
-    | undefined
-    | Promise<NOTIFICATION_TYPE | null | undefined>;
+    | void
+    | Promise<NOTIFICATION_TYPE | null | void>;
 
   user: (
     parent: Notification,
diff --git a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
index f86bf004..4a4e8e5b 100644
--- a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
+++ b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
@@ -23,7 +23,7 @@ export namespace QueryResolvers {
     args: ArgsCreateUser,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => User | null | undefined | Promise<User | null | undefined>;
+  ) => User | null | Promise<User | null>;
 
   export interface Type {
     createUser: (
@@ -245,14 +245,14 @@ export namespace AddMemberPayloadResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | Promise<string | null>;
 
   export type ExistingUserInviteSentResolver = (
     parent: AddMemberPayload,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | Promise<boolean | null>;
 
   export interface Type {
     newUserId: (
@@ -382,7 +382,7 @@ export namespace AddMemberPayloadResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | Promise<string | null>;
 
   export interface Type {
     json: (
@@ -497,27 +497,21 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number | null | undefined | Promise<Number | null | undefined>;
+  ) => Number | null | Promise<Number | null>;
 
   export type Custom_array_nullableResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Number | null | undefined>
-    | null
-    | undefined
-    | Promise<Array<Number | null | undefined> | null | undefined>;
+  ) => Array<Number | null> | null | Promise<Array<Number | null> | null>;
 
   export type Custom_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Number | null | undefined>
-    | Promise<Array<Number | null | undefined>>;
+  ) => Array<Number | null> | Promise<Array<Number | null>>;
 
   export type Custom_with_argResolver = (
     parent: undefined,
@@ -545,27 +539,21 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | Promise<boolean | null>;
 
   export type Scalar_array_nullableResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<boolean | null | undefined>
-    | null
-    | undefined
-    | Promise<Array<boolean | null | undefined> | null | undefined>;
+  ) => Array<boolean | null> | null | Promise<Array<boolean | null> | null>;
 
   export type Scalar_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<boolean | null | undefined>
-    | Promise<Array<boolean | null | undefined>>;
+  ) => Array<boolean | null> | Promise<Array<boolean | null>>;
 
   export type Scalar_with_argResolver = (
     parent: undefined,
@@ -698,14 +686,14 @@ export namespace NumberResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | Promise<string | null>;
 
   export type ValueResolver = (
     parent: Number,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export interface Type {
     id: (
@@ -908,7 +896,7 @@ export namespace ProfessorResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | Promise<string | null>;
 
   export interface Type {
     degree: (
@@ -1009,7 +997,7 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => User | null | undefined | Promise<User | null | undefined>;
+  ) => User | null | Promise<User | null>;
 
   export interface Type {
     createUser: (
@@ -1146,7 +1134,7 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => NumberNode | null | undefined | Promise<NumberNode | null | undefined>;
+  ) => NumberNode | null | Promise<NumberNode | null>;
 
   export type Custom_array_nullableResolver = (
     parent: undefined,
@@ -1154,19 +1142,16 @@ export namespace QueryResolvers {
     ctx: Context,
     info: GraphQLResolveInfo
   ) =>
-    | Array<NumberNode | null | undefined>
+    | Array<NumberNode | null>
     | null
-    | undefined
-    | Promise<Array<NumberNode | null | undefined> | null | undefined>;
+    | Promise<Array<NumberNode | null> | null>;
 
   export type Custom_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<NumberNode | null | undefined>
-    | Promise<Array<NumberNode | null | undefined>>;
+  ) => Array<NumberNode | null> | Promise<Array<NumberNode | null>>;
 
   export type Custom_with_argResolver = (
     parent: undefined,
@@ -1194,27 +1179,21 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | Promise<boolean | null>;
 
   export type Scalar_array_nullableResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<boolean | null | undefined>
-    | null
-    | undefined
-    | Promise<Array<boolean | null | undefined> | null | undefined>;
+  ) => Array<boolean | null> | null | Promise<Array<boolean | null> | null>;
 
   export type Scalar_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<boolean | null | undefined>
-    | Promise<Array<boolean | null | undefined>>;
+  ) => Array<boolean | null> | Promise<Array<boolean | null>>;
 
   export type Scalar_with_argResolver = (
     parent: undefined,
@@ -1347,14 +1326,14 @@ export namespace NumberResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | Promise<string | null>;
 
   export type ValueResolver = (
     parent: NumberNode,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export interface Type {
     id: (
@@ -1512,27 +1491,21 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number | null | undefined | Promise<Number | null | undefined>;
+  ) => Number | null | Promise<Number | null>;
 
   export type Custom_array_nullableResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Number | null | undefined>
-    | null
-    | undefined
-    | Promise<Array<Number | null | undefined> | null | undefined>;
+  ) => Array<Number | null> | null | Promise<Array<Number | null> | null>;
 
   export type Custom_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Number | null | undefined>
-    | Promise<Array<Number | null | undefined>>;
+  ) => Array<Number | null> | Promise<Array<Number | null>>;
 
   export type Custom_with_argResolver = (
     parent: undefined,
@@ -1560,27 +1533,21 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | Promise<boolean | null>;
 
   export type Scalar_array_nullableResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<boolean | null | undefined>
-    | null
-    | undefined
-    | Promise<Array<boolean | null | undefined> | null | undefined>;
+  ) => Array<boolean | null> | null | Promise<Array<boolean | null> | null>;
 
   export type Scalar_array_requiredResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<boolean | null | undefined>
-    | Promise<Array<boolean | null | undefined>>;
+  ) => Array<boolean | null> | Promise<Array<boolean | null>>;
 
   export type Scalar_with_argResolver = (
     parent: undefined,
@@ -1713,14 +1680,14 @@ export namespace NumberResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | Promise<string | null>;
 
   export type ValueResolver = (
     parent: Number,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export interface Type {
     id: (
diff --git a/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap b/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
index e15e8669..e992ff4a 100644
--- a/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
+++ b/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
@@ -113,14 +113,14 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Viewer | null | undefined | Promise<Viewer | null | undefined>;
+  ) => Viewer | null | Promise<Viewer | null>;
 
   export type MyLocationResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Location | null | undefined | Promise<Location | null | undefined>;
+  ) => Location | null | Promise<Location | null>;
 
   export interface Type {
     topExperiences: (
@@ -206,11 +206,7 @@ export namespace ExperienceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | ExperienceCategory
-    | null
-    | undefined
-    | Promise<ExperienceCategory | null | undefined>;
+  ) => ExperienceCategory | null | Promise<ExperienceCategory | null>;
 
   export type TitleResolver = (
     parent: Experience,
@@ -352,7 +348,7 @@ export namespace ExperienceCategoryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Experience | null | undefined | Promise<Experience | null | undefined>;
+  ) => Experience | null | Promise<Experience | null>;
 
   export interface Type {
     id: (
@@ -422,14 +418,14 @@ export namespace LocationResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | Promise<string | null>;
 
   export type DirectionsResolver = (
     parent: Location,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | Promise<string | null>;
 
   export interface Type {
     id: (
@@ -691,7 +687,7 @@ export namespace HomeResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | Promise<string | null>;
 
   export type DescriptionResolver = (
     parent: Home,
@@ -712,7 +708,7 @@ export namespace HomeResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export type PicturesResolver = (
     parent: Home,
@@ -945,7 +941,7 @@ export namespace NeighbourhoodResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture | null | undefined | Promise<Picture | null | undefined>;
+  ) => Picture | null | Promise<Picture | null>;
 
   export type CityResolver = (
     parent: Neighbourhood,
@@ -1160,11 +1156,7 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Booking>
-    | null
-    | undefined
-    | Promise<Array<Booking> | null | undefined>;
+  ) => Array<Booking> | null | Promise<Array<Booking> | null>;
 
   export type CreatedAtResolver = (
     parent: User,
@@ -1192,11 +1184,7 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Experience>
-    | null
-    | undefined
-    | Promise<Array<Experience> | null | undefined>;
+  ) => Array<Experience> | null | Promise<Array<Experience> | null>;
 
   export type IdResolver = (
     parent: User,
@@ -1231,33 +1219,21 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Notification>
-    | null
-    | undefined
-    | Promise<Array<Notification> | null | undefined>;
+  ) => Array<Notification> | null | Promise<Array<Notification> | null>;
 
   export type OwnedPlacesResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Place>
-    | null
-    | undefined
-    | Promise<Array<Place> | null | undefined>;
+  ) => Array<Place> | null | Promise<Array<Place> | null>;
 
   export type PaymentAccountResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<PaymentAccount>
-    | null
-    | undefined
-    | Promise<Array<PaymentAccount> | null | undefined>;
+  ) => Array<PaymentAccount> | null | Promise<Array<PaymentAccount> | null>;
 
   export type PhoneResolver = (
     parent: User,
@@ -1271,43 +1247,35 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture | null | undefined | Promise<Picture | null | undefined>;
+  ) => Picture | null | Promise<Picture | null>;
 
   export type ReceivedMessagesResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Message>
-    | null
-    | undefined
-    | Promise<Array<Message> | null | undefined>;
+  ) => Array<Message> | null | Promise<Array<Message> | null>;
 
   export type ResponseRateResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export type ResponseTimeResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export type SentMessagesResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Message>
-    | null
-    | undefined
-    | Promise<Array<Message> | null | undefined>;
+  ) => Array<Message> | null | Promise<Array<Message> | null>;
 
   export type UpdatedAtResolver = (
     parent: User,
@@ -1647,14 +1615,14 @@ export namespace PlaceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | Promise<string | null>;
 
   export type SizeResolver = (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PLACE_SIZES | null | undefined | Promise<PLACE_SIZES | null | undefined>;
+  ) => PLACE_SIZES | null | Promise<PLACE_SIZES | null>;
 
   export type ShortDescriptionResolver = (
     parent: Place,
@@ -1752,25 +1720,21 @@ export namespace PlaceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | GuestRequirements
-    | null
-    | undefined
-    | Promise<GuestRequirements | null | undefined>;
+  ) => GuestRequirements | null | Promise<GuestRequirements | null>;
 
   export type PoliciesResolver = (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Policies | null | undefined | Promise<Policies | null | undefined>;
+  ) => Policies | null | Promise<Policies | null>;
 
   export type HouseRulesResolver = (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => HouseRules | null | undefined | Promise<HouseRules | null | undefined>;
+  ) => HouseRules | null | Promise<HouseRules | null>;
 
   export type BookingsResolver = (
     parent: Place,
@@ -1784,11 +1748,7 @@ export namespace PlaceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Picture>
-    | null
-    | undefined
-    | Promise<Array<Picture> | null | undefined>;
+  ) => Array<Picture> | null | Promise<Array<Picture> | null>;
 
   export type PopularityResolver = (
     parent: Place,
@@ -2642,21 +2602,21 @@ export namespace PricingResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export type CurrencyResolver = (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => CURRENCY | null | undefined | Promise<CURRENCY | null | undefined>;
+  ) => CURRENCY | null | Promise<CURRENCY | null>;
 
   export type ExtraGuestsResolver = (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export type IdResolver = (
     parent: Pricing,
@@ -2670,7 +2630,7 @@ export namespace PricingResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export type PerNightResolver = (
     parent: Pricing,
@@ -2684,7 +2644,7 @@ export namespace PricingResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export type SmartPricingResolver = (
     parent: Pricing,
@@ -2698,14 +2658,14 @@ export namespace PricingResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export type WeeklyDiscountResolver = (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | undefined | Promise<number | null | undefined>;
+  ) => number | null | Promise<number | null>;
 
   export interface Type {
     averageMonthly: (
@@ -3034,7 +2994,7 @@ export namespace HouseRulesResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | undefined | Promise<string | null | undefined>;
+  ) => string | null | Promise<string | null>;
 
   export type CreatedAtResolver = (
     parent: HouseRules,
@@ -3055,35 +3015,35 @@ export namespace HouseRulesResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | Promise<boolean | null>;
 
   export type PetsAllowedResolver = (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | Promise<boolean | null>;
 
   export type SmokingAllowedResolver = (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | Promise<boolean | null>;
 
   export type SuitableForChildrenResolver = (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | Promise<boolean | null>;
 
   export type SuitableForInfantsResolver = (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+  ) => boolean | null | Promise<boolean | null>;
 
   export type UpdatedAtResolver = (
     parent: HouseRules,
@@ -3273,11 +3233,7 @@ export namespace PaymentAccountResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | PAYMENT_PROVIDER
-    | null
-    | undefined
-    | Promise<PAYMENT_PROVIDER | null | undefined>;
+  ) => PAYMENT_PROVIDER | null | Promise<PAYMENT_PROVIDER | null>;
 
   export type UserResolver = (
     parent: PaymentAccount,
@@ -3298,22 +3254,14 @@ export namespace PaymentAccountResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | PaypalInformation
-    | null
-    | undefined
-    | Promise<PaypalInformation | null | undefined>;
+  ) => PaypalInformation | null | Promise<PaypalInformation | null>;
 
   export type CreditcardResolver = (
     parent: PaymentAccount,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | CreditCardInformation
-    | null
-    | undefined
-    | Promise<CreditCardInformation | null | undefined>;
+  ) => CreditCardInformation | null | Promise<CreditCardInformation | null>;
 
   export interface Type {
     id: (
@@ -3523,11 +3471,7 @@ export namespace CreditCardInformationResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | PaymentAccount
-    | null
-    | undefined
-    | Promise<PaymentAccount | null | undefined>;
+  ) => PaymentAccount | null | Promise<PaymentAccount | null>;
 
   export type PostalCodeResolver = (
     parent: CreditCardInformation,
@@ -3671,11 +3615,7 @@ export namespace NotificationResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | NOTIFICATION_TYPE
-    | null
-    | undefined
-    | Promise<NOTIFICATION_TYPE | null | undefined>;
+  ) => NOTIFICATION_TYPE | null | Promise<NOTIFICATION_TYPE | null>;
 
   export type UserResolver = (
     parent: Notification,

From 4dadf861384235914fd7bdcd36a7682c994f1f36 Mon Sep 17 00:00:00 2001
From: Jason Kuhrt <jasonkuhrt@me.com>
Date: Wed, 2 Jan 2019 22:56:09 -0500
Subject: [PATCH 4/8] fix: other case of return type field generation

---
 .../src/generators/flow-generator.ts          |   2 +-
 .../graphqlgen/src/generators/ts-generator.ts |   2 +-
 .../flow/__snapshots__/basic.test.ts.snap     |  57 +++----
 .../__snapshots__/large-schema.test.ts.snap   | 118 +++++---------
 .../__snapshots__/basic.test.ts.snap          |  95 ++++-------
 .../__snapshots__/large-schema.test.ts.snap   | 150 +++++-------------
 6 files changed, 140 insertions(+), 284 deletions(-)

diff --git a/packages/graphqlgen/src/generators/flow-generator.ts b/packages/graphqlgen/src/generators/flow-generator.ts
index 6226c8e0..1d05495d 100644
--- a/packages/graphqlgen/src/generators/flow-generator.ts
+++ b/packages/graphqlgen/src/generators/flow-generator.ts
@@ -301,7 +301,7 @@ function renderResolverTypeInterfaceFunction(
     ctx: ${getContextName(context)},
     info: GraphQLResolveInfo,
   )`
-  const returnType = printFieldLikeFlowType(field, modelMap)
+  const returnType = printFieldLikeReturnType(field, modelMap)
 
   if (type.name === 'Subscription') {
     return `
diff --git a/packages/graphqlgen/src/generators/ts-generator.ts b/packages/graphqlgen/src/generators/ts-generator.ts
index 0fa3f2f3..3f7448ea 100644
--- a/packages/graphqlgen/src/generators/ts-generator.ts
+++ b/packages/graphqlgen/src/generators/ts-generator.ts
@@ -313,7 +313,7 @@ function renderResolverTypeInterfaceFunction(
     info: GraphQLResolveInfo,
   )
   `
-  const returnType = printFieldLikeType(field, modelMap)
+  const returnType = printFieldLikeReturnType(field, modelMap)
 
   if (type.name === 'Subscription') {
     return `
diff --git a/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap b/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
index fba90ebf..8f2ffc59 100644
--- a/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
+++ b/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
@@ -32,7 +32,7 @@ export interface Query_Resolvers {
     args: Query_Args_CreateUser,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => User | null | void | Promise<User | null | void>;
+  ) => User | null | Promise<User | null>;
 }
 
 // Types for User
@@ -213,7 +213,7 @@ export interface AddMemberPayload_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | void | Promise<string | null | void>;
+  ) => string | null | Promise<string | null>;
 }
 
 export interface Resolvers {
@@ -409,25 +409,21 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Number | null | void | Promise<Number | null | void>;
+  ) => Number | null | Promise<Number | null>;
 
   custom_array_nullable: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Number | null | void>
-    | null
-    | void
-    | Promise<Array<Number | null | void> | null | void>;
+  ) => Array<Number | null> | null | Promise<Array<Number | null> | null>;
 
   custom_array_required: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Number | null | void> | Promise<Array<Number | null | void>>;
+  ) => Array<Number | null> | Promise<Array<Number | null>>;
 
   custom_with_arg: (
     parent: {},
@@ -455,25 +451,21 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | void | Promise<boolean | null | void>;
+  ) => boolean | null | Promise<boolean | null>;
 
   scalar_array_nullable: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<boolean | null | void>
-    | null
-    | void
-    | Promise<Array<boolean | null | void> | null | void>;
+  ) => Array<boolean | null> | null | Promise<Array<boolean | null> | null>;
 
   scalar_array_required: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<boolean | null | void> | Promise<Array<boolean | null | void>>;
+  ) => Array<boolean | null> | Promise<Array<boolean | null>>;
 
   scalar_with_arg: (
     parent: {},
@@ -516,14 +508,14 @@ export interface Number_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | void | Promise<string | null | void>;
+  ) => string | null | Promise<string | null>;
 
   value: (
     parent: Number,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | void | Promise<number | null | void>;
+  ) => number | null | Promise<number | null>;
 }
 
 export interface Resolvers {
@@ -714,7 +706,7 @@ export interface Professor_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | void | Promise<string | null | void>;
+  ) => string | null | Promise<string | null>;
 }
 
 export interface Resolvers {
@@ -814,7 +806,7 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => User | null | void | Promise<User | null | void>;
+  ) => User | null | Promise<User | null>;
 }
 
 // Types for User
@@ -1031,7 +1023,7 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => NumberNode | null | void | Promise<NumberNode | null | void>;
+  ) => NumberNode | null | Promise<NumberNode | null>;
 
   custom_array_nullable: (
     parent: {},
@@ -1039,19 +1031,16 @@ export interface Query_Resolvers {
     ctx: Context,
     info: GraphQLResolveInfo
   ) =>
-    | Array<NumberNode | null | void>
+    | Array<NumberNode | null>
     | null
-    | void
-    | Promise<Array<NumberNode | null | void> | null | void>;
+    | Promise<Array<NumberNode | null> | null>;
 
   custom_array_required: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<NumberNode | null | void>
-    | Promise<Array<NumberNode | null | void>>;
+  ) => Array<NumberNode | null> | Promise<Array<NumberNode | null>>;
 
   custom_with_arg: (
     parent: {},
@@ -1079,25 +1068,21 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | void | Promise<boolean | null | void>;
+  ) => boolean | null | Promise<boolean | null>;
 
   scalar_array_nullable: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<boolean | null | void>
-    | null
-    | void
-    | Promise<Array<boolean | null | void> | null | void>;
+  ) => Array<boolean | null> | null | Promise<Array<boolean | null> | null>;
 
   scalar_array_required: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<boolean | null | void> | Promise<Array<boolean | null | void>>;
+  ) => Array<boolean | null> | Promise<Array<boolean | null>>;
 
   scalar_with_arg: (
     parent: {},
@@ -1140,14 +1125,14 @@ export interface Number_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | void | Promise<string | null | void>;
+  ) => string | null | Promise<string | null>;
 
   value: (
     parent: NumberNode,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | void | Promise<number | null | void>;
+  ) => number | null | Promise<number | null>;
 }
 
 export interface Resolvers {
diff --git a/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap b/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
index ca8e370d..28b78d34 100644
--- a/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
+++ b/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
@@ -171,14 +171,14 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Viewer | null | void | Promise<Viewer | null | void>;
+  ) => Viewer | null | Promise<Viewer | null>;
 
   myLocation: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Location | null | void | Promise<Location | null | void>;
+  ) => Location | null | Promise<Location | null>;
 }
 
 // Types for Experience
@@ -263,11 +263,7 @@ export interface Experience_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | ExperienceCategory
-    | null
-    | void
-    | Promise<ExperienceCategory | null | void>;
+  ) => ExperienceCategory | null | Promise<ExperienceCategory | null>;
 
   title: (
     parent: Experience,
@@ -376,7 +372,7 @@ export interface ExperienceCategory_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Experience | null | void | Promise<Experience | null | void>;
+  ) => Experience | null | Promise<Experience | null>;
 }
 
 // Types for Location
@@ -452,14 +448,14 @@ export interface Location_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | void | Promise<string | null | void>;
+  ) => string | null | Promise<string | null>;
 
   directions: (
     parent: Location,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | void | Promise<string | null | void>;
+  ) => string | null | Promise<string | null>;
 }
 
 // Types for Review
@@ -732,7 +728,7 @@ export interface Home_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | void | Promise<string | null | void>;
+  ) => string | null | Promise<string | null>;
 
   description: (
     parent: Home,
@@ -753,7 +749,7 @@ export interface Home_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | void | Promise<number | null | void>;
+  ) => number | null | Promise<number | null>;
 
   pictures: (
     parent: Home,
@@ -984,7 +980,7 @@ export interface Neighbourhood_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture | null | void | Promise<Picture | null | void>;
+  ) => Picture | null | Promise<Picture | null>;
 
   city: (
     parent: Neighbourhood,
@@ -1286,7 +1282,7 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Booking> | null | void | Promise<Array<Booking> | null | void>;
+  ) => Array<Booking> | null | Promise<Array<Booking> | null>;
 
   createdAt: (
     parent: User,
@@ -1314,11 +1310,7 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Experience>
-    | null
-    | void
-    | Promise<Array<Experience> | null | void>;
+  ) => Array<Experience> | null | Promise<Array<Experience> | null>;
 
   id: (
     parent: User,
@@ -1353,29 +1345,21 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<Notification>
-    | null
-    | void
-    | Promise<Array<Notification> | null | void>;
+  ) => Array<Notification> | null | Promise<Array<Notification> | null>;
 
   ownedPlaces: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Place> | null | void | Promise<Array<Place> | null | void>;
+  ) => Array<Place> | null | Promise<Array<Place> | null>;
 
   paymentAccount: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | Array<PaymentAccount>
-    | null
-    | void
-    | Promise<Array<PaymentAccount> | null | void>;
+  ) => Array<PaymentAccount> | null | Promise<Array<PaymentAccount> | null>;
 
   phone: (
     parent: User,
@@ -1389,35 +1373,35 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Picture | null | void | Promise<Picture | null | void>;
+  ) => Picture | null | Promise<Picture | null>;
 
   receivedMessages: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Message> | null | void | Promise<Array<Message> | null | void>;
+  ) => Array<Message> | null | Promise<Array<Message> | null>;
 
   responseRate: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | void | Promise<number | null | void>;
+  ) => number | null | Promise<number | null>;
 
   responseTime: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | void | Promise<number | null | void>;
+  ) => number | null | Promise<number | null>;
 
   sentMessages: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Message> | null | void | Promise<Array<Message> | null | void>;
+  ) => Array<Message> | null | Promise<Array<Message> | null>;
 
   updatedAt: (
     parent: User,
@@ -1741,14 +1725,14 @@ export interface Place_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | void | Promise<string | null | void>;
+  ) => string | null | Promise<string | null>;
 
   size: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PLACE_SIZES | null | void | Promise<PLACE_SIZES | null | void>;
+  ) => PLACE_SIZES | null | Promise<PLACE_SIZES | null>;
 
   shortDescription: (
     parent: Place,
@@ -1846,25 +1830,21 @@ export interface Place_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | GuestRequirements
-    | null
-    | void
-    | Promise<GuestRequirements | null | void>;
+  ) => GuestRequirements | null | Promise<GuestRequirements | null>;
 
   policies: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Policies | null | void | Promise<Policies | null | void>;
+  ) => Policies | null | Promise<Policies | null>;
 
   houseRules: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => HouseRules | null | void | Promise<HouseRules | null | void>;
+  ) => HouseRules | null | Promise<HouseRules | null>;
 
   bookings: (
     parent: Place,
@@ -1878,7 +1858,7 @@ export interface Place_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Picture> | null | void | Promise<Array<Picture> | null | void>;
+  ) => Array<Picture> | null | Promise<Array<Picture> | null>;
 
   popularity: (
     parent: Place,
@@ -2653,21 +2633,21 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | void | Promise<number | null | void>;
+  ) => number | null | Promise<number | null>;
 
   currency: (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => CURRENCY | null | void | Promise<CURRENCY | null | void>;
+  ) => CURRENCY | null | Promise<CURRENCY | null>;
 
   extraGuests: (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | void | Promise<number | null | void>;
+  ) => number | null | Promise<number | null>;
 
   id: (
     parent: Pricing,
@@ -2681,7 +2661,7 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | void | Promise<number | null | void>;
+  ) => number | null | Promise<number | null>;
 
   perNight: (
     parent: Pricing,
@@ -2695,7 +2675,7 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | void | Promise<number | null | void>;
+  ) => number | null | Promise<number | null>;
 
   smartPricing: (
     parent: Pricing,
@@ -2709,14 +2689,14 @@ export interface Pricing_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | void | Promise<number | null | void>;
+  ) => number | null | Promise<number | null>;
 
   weeklyDiscount: (
     parent: Pricing,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => number | null | void | Promise<number | null | void>;
+  ) => number | null | Promise<number | null>;
 }
 
 // Types for PlaceViews
@@ -3011,7 +2991,7 @@ export interface HouseRules_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => string | null | void | Promise<string | null | void>;
+  ) => string | null | Promise<string | null>;
 
   createdAt: (
     parent: HouseRules,
@@ -3032,35 +3012,35 @@ export interface HouseRules_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | void | Promise<boolean | null | void>;
+  ) => boolean | null | Promise<boolean | null>;
 
   petsAllowed: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | void | Promise<boolean | null | void>;
+  ) => boolean | null | Promise<boolean | null>;
 
   smokingAllowed: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | void | Promise<boolean | null | void>;
+  ) => boolean | null | Promise<boolean | null>;
 
   suitableForChildren: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | void | Promise<boolean | null | void>;
+  ) => boolean | null | Promise<boolean | null>;
 
   suitableForInfants: (
     parent: HouseRules,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => boolean | null | void | Promise<boolean | null | void>;
+  ) => boolean | null | Promise<boolean | null>;
 
   updatedAt: (
     parent: HouseRules,
@@ -3234,7 +3214,7 @@ export interface PaymentAccount_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PAYMENT_PROVIDER | null | void | Promise<PAYMENT_PROVIDER | null | void>;
+  ) => PAYMENT_PROVIDER | null | Promise<PAYMENT_PROVIDER | null>;
 
   user: (
     parent: PaymentAccount,
@@ -3255,22 +3235,14 @@ export interface PaymentAccount_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | PaypalInformation
-    | null
-    | void
-    | Promise<PaypalInformation | null | void>;
+  ) => PaypalInformation | null | Promise<PaypalInformation | null>;
 
   creditcard: (
     parent: PaymentAccount,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | CreditCardInformation
-    | null
-    | void
-    | Promise<CreditCardInformation | null | void>;
+  ) => CreditCardInformation | null | Promise<CreditCardInformation | null>;
 }
 
 // Types for PaypalInformation
@@ -3494,7 +3466,7 @@ export interface CreditCardInformation_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => PaymentAccount | null | void | Promise<PaymentAccount | null | void>;
+  ) => PaymentAccount | null | Promise<PaymentAccount | null>;
 
   postalCode: (
     parent: CreditCardInformation,
@@ -3598,11 +3570,7 @@ export interface Notification_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) =>
-    | NOTIFICATION_TYPE
-    | null
-    | void
-    | Promise<NOTIFICATION_TYPE | null | void>;
+  ) => NOTIFICATION_TYPE | null | Promise<NOTIFICATION_TYPE | null>;
 
   user: (
     parent: Notification,
diff --git a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
index 4a4e8e5b..a98aa78e 100644
--- a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
+++ b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
@@ -31,7 +31,7 @@ export namespace QueryResolvers {
       args: ArgsCreateUser,
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => User | null | undefined | Promise<User | null | undefined>;
+    ) => User | null | Promise<User | null>;
   }
 }
 
@@ -260,14 +260,14 @@ export namespace AddMemberPayloadResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | undefined | Promise<string | null | undefined>;
+    ) => string | null | Promise<string | null>;
 
     existingUserInviteSent: (
       parent: AddMemberPayload,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+    ) => boolean | null | Promise<boolean | null>;
   }
 }
 
@@ -390,7 +390,7 @@ export namespace AddMemberPayloadResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | undefined | Promise<string | null | undefined>;
+    ) => string | null | Promise<string | null>;
   }
 }
 
@@ -589,27 +589,21 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Number | null | undefined | Promise<Number | null | undefined>;
+    ) => Number | null | Promise<Number | null>;
 
     custom_array_nullable: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<Number | null | undefined>
-      | null
-      | undefined
-      | Promise<Array<Number | null | undefined> | null | undefined>;
+    ) => Array<Number | null> | null | Promise<Array<Number | null> | null>;
 
     custom_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<Number | null | undefined>
-      | Promise<Array<Number | null | undefined>>;
+    ) => Array<Number | null> | Promise<Array<Number | null>>;
 
     custom_with_arg: (
       parent: undefined,
@@ -637,27 +631,21 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+    ) => boolean | null | Promise<boolean | null>;
 
     scalar_array_nullable: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<boolean | null | undefined>
-      | null
-      | undefined
-      | Promise<Array<boolean | null | undefined> | null | undefined>;
+    ) => Array<boolean | null> | null | Promise<Array<boolean | null> | null>;
 
     scalar_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<boolean | null | undefined>
-      | Promise<Array<boolean | null | undefined>>;
+    ) => Array<boolean | null> | Promise<Array<boolean | null>>;
 
     scalar_with_arg: (
       parent: undefined,
@@ -701,14 +689,14 @@ export namespace NumberResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | undefined | Promise<string | null | undefined>;
+    ) => string | null | Promise<string | null>;
 
     value: (
       parent: Number,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
   }
 }
 
@@ -904,7 +892,7 @@ export namespace ProfessorResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | undefined | Promise<string | null | undefined>;
+    ) => string | null | Promise<string | null>;
   }
 }
 
@@ -1005,7 +993,7 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => User | null | undefined | Promise<User | null | undefined>;
+    ) => User | null | Promise<User | null>;
   }
 }
 
@@ -1229,7 +1217,7 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => NumberNode | null | undefined | Promise<NumberNode | null | undefined>;
+    ) => NumberNode | null | Promise<NumberNode | null>;
 
     custom_array_nullable: (
       parent: undefined,
@@ -1237,19 +1225,16 @@ export namespace QueryResolvers {
       ctx: Context,
       info: GraphQLResolveInfo
     ) =>
-      | Array<NumberNode | null | undefined>
+      | Array<NumberNode | null>
       | null
-      | undefined
-      | Promise<Array<NumberNode | null | undefined> | null | undefined>;
+      | Promise<Array<NumberNode | null> | null>;
 
     custom_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<NumberNode | null | undefined>
-      | Promise<Array<NumberNode | null | undefined>>;
+    ) => Array<NumberNode | null> | Promise<Array<NumberNode | null>>;
 
     custom_with_arg: (
       parent: undefined,
@@ -1277,27 +1262,21 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+    ) => boolean | null | Promise<boolean | null>;
 
     scalar_array_nullable: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<boolean | null | undefined>
-      | null
-      | undefined
-      | Promise<Array<boolean | null | undefined> | null | undefined>;
+    ) => Array<boolean | null> | null | Promise<Array<boolean | null> | null>;
 
     scalar_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<boolean | null | undefined>
-      | Promise<Array<boolean | null | undefined>>;
+    ) => Array<boolean | null> | Promise<Array<boolean | null>>;
 
     scalar_with_arg: (
       parent: undefined,
@@ -1341,14 +1320,14 @@ export namespace NumberResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | undefined | Promise<string | null | undefined>;
+    ) => string | null | Promise<string | null>;
 
     value: (
       parent: NumberNode,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
   }
 }
 
@@ -1583,27 +1562,21 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Number | null | undefined | Promise<Number | null | undefined>;
+    ) => Number | null | Promise<Number | null>;
 
     custom_array_nullable: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<Number | null | undefined>
-      | null
-      | undefined
-      | Promise<Array<Number | null | undefined> | null | undefined>;
+    ) => Array<Number | null> | null | Promise<Array<Number | null> | null>;
 
     custom_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<Number | null | undefined>
-      | Promise<Array<Number | null | undefined>>;
+    ) => Array<Number | null> | Promise<Array<Number | null>>;
 
     custom_with_arg: (
       parent: undefined,
@@ -1631,27 +1604,21 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+    ) => boolean | null | Promise<boolean | null>;
 
     scalar_array_nullable: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<boolean | null | undefined>
-      | null
-      | undefined
-      | Promise<Array<boolean | null | undefined> | null | undefined>;
+    ) => Array<boolean | null> | null | Promise<Array<boolean | null> | null>;
 
     scalar_array_required: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<boolean | null | undefined>
-      | Promise<Array<boolean | null | undefined>>;
+    ) => Array<boolean | null> | Promise<Array<boolean | null>>;
 
     scalar_with_arg: (
       parent: undefined,
@@ -1695,14 +1662,14 @@ export namespace NumberResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | undefined | Promise<string | null | undefined>;
+    ) => string | null | Promise<string | null>;
 
     value: (
       parent: Number,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
   }
 }
 
diff --git a/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap b/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
index e992ff4a..129c286c 100644
--- a/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
+++ b/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
@@ -170,14 +170,14 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Viewer | null | undefined | Promise<Viewer | null | undefined>;
+    ) => Viewer | null | Promise<Viewer | null>;
 
     myLocation: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Location | null | undefined | Promise<Location | null | undefined>;
+    ) => Location | null | Promise<Location | null>;
   }
 }
 
@@ -263,11 +263,7 @@ export namespace ExperienceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | ExperienceCategory
-      | null
-      | undefined
-      | Promise<ExperienceCategory | null | undefined>;
+    ) => ExperienceCategory | null | Promise<ExperienceCategory | null>;
 
     title: (
       parent: Experience,
@@ -377,7 +373,7 @@ export namespace ExperienceCategoryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Experience | null | undefined | Promise<Experience | null | undefined>;
+    ) => Experience | null | Promise<Experience | null>;
   }
 }
 
@@ -454,14 +450,14 @@ export namespace LocationResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | undefined | Promise<string | null | undefined>;
+    ) => string | null | Promise<string | null>;
 
     directions: (
       parent: Location,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | undefined | Promise<string | null | undefined>;
+    ) => string | null | Promise<string | null>;
   }
 }
 
@@ -737,7 +733,7 @@ export namespace HomeResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | undefined | Promise<string | null | undefined>;
+    ) => string | null | Promise<string | null>;
 
     description: (
       parent: Home,
@@ -758,7 +754,7 @@ export namespace HomeResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
 
     pictures: (
       parent: Home,
@@ -991,7 +987,7 @@ export namespace NeighbourhoodResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Picture | null | undefined | Promise<Picture | null | undefined>;
+    ) => Picture | null | Promise<Picture | null>;
 
     city: (
       parent: Neighbourhood,
@@ -1297,11 +1293,7 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<Booking>
-      | null
-      | undefined
-      | Promise<Array<Booking> | null | undefined>;
+    ) => Array<Booking> | null | Promise<Array<Booking> | null>;
 
     createdAt: (
       parent: User,
@@ -1329,11 +1321,7 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<Experience>
-      | null
-      | undefined
-      | Promise<Array<Experience> | null | undefined>;
+    ) => Array<Experience> | null | Promise<Array<Experience> | null>;
 
     id: (
       parent: User,
@@ -1368,33 +1356,21 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<Notification>
-      | null
-      | undefined
-      | Promise<Array<Notification> | null | undefined>;
+    ) => Array<Notification> | null | Promise<Array<Notification> | null>;
 
     ownedPlaces: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<Place>
-      | null
-      | undefined
-      | Promise<Array<Place> | null | undefined>;
+    ) => Array<Place> | null | Promise<Array<Place> | null>;
 
     paymentAccount: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<PaymentAccount>
-      | null
-      | undefined
-      | Promise<Array<PaymentAccount> | null | undefined>;
+    ) => Array<PaymentAccount> | null | Promise<Array<PaymentAccount> | null>;
 
     phone: (
       parent: User,
@@ -1408,43 +1384,35 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Picture | null | undefined | Promise<Picture | null | undefined>;
+    ) => Picture | null | Promise<Picture | null>;
 
     receivedMessages: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<Message>
-      | null
-      | undefined
-      | Promise<Array<Message> | null | undefined>;
+    ) => Array<Message> | null | Promise<Array<Message> | null>;
 
     responseRate: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
 
     responseTime: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
 
     sentMessages: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<Message>
-      | null
-      | undefined
-      | Promise<Array<Message> | null | undefined>;
+    ) => Array<Message> | null | Promise<Array<Message> | null>;
 
     updatedAt: (
       parent: User,
@@ -1770,18 +1738,14 @@ export namespace PlaceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | undefined | Promise<string | null | undefined>;
+    ) => string | null | Promise<string | null>;
 
     size: (
       parent: Place,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | PLACE_SIZES
-      | null
-      | undefined
-      | Promise<PLACE_SIZES | null | undefined>;
+    ) => PLACE_SIZES | null | Promise<PLACE_SIZES | null>;
 
     shortDescription: (
       parent: Place,
@@ -1879,25 +1843,21 @@ export namespace PlaceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | GuestRequirements
-      | null
-      | undefined
-      | Promise<GuestRequirements | null | undefined>;
+    ) => GuestRequirements | null | Promise<GuestRequirements | null>;
 
     policies: (
       parent: Place,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Policies | null | undefined | Promise<Policies | null | undefined>;
+    ) => Policies | null | Promise<Policies | null>;
 
     houseRules: (
       parent: Place,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => HouseRules | null | undefined | Promise<HouseRules | null | undefined>;
+    ) => HouseRules | null | Promise<HouseRules | null>;
 
     bookings: (
       parent: Place,
@@ -1911,11 +1871,7 @@ export namespace PlaceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | Array<Picture>
-      | null
-      | undefined
-      | Promise<Array<Picture> | null | undefined>;
+    ) => Array<Picture> | null | Promise<Array<Picture> | null>;
 
     popularity: (
       parent: Place,
@@ -2694,21 +2650,21 @@ export namespace PricingResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
 
     currency: (
       parent: Pricing,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => CURRENCY | null | undefined | Promise<CURRENCY | null | undefined>;
+    ) => CURRENCY | null | Promise<CURRENCY | null>;
 
     extraGuests: (
       parent: Pricing,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
 
     id: (
       parent: Pricing,
@@ -2722,7 +2678,7 @@ export namespace PricingResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
 
     perNight: (
       parent: Pricing,
@@ -2736,7 +2692,7 @@ export namespace PricingResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
 
     smartPricing: (
       parent: Pricing,
@@ -2750,14 +2706,14 @@ export namespace PricingResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
 
     weeklyDiscount: (
       parent: Pricing,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => number | null | undefined | Promise<number | null | undefined>;
+    ) => number | null | Promise<number | null>;
   }
 }
 
@@ -3058,7 +3014,7 @@ export namespace HouseRulesResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => string | null | undefined | Promise<string | null | undefined>;
+    ) => string | null | Promise<string | null>;
 
     createdAt: (
       parent: HouseRules,
@@ -3079,35 +3035,35 @@ export namespace HouseRulesResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+    ) => boolean | null | Promise<boolean | null>;
 
     petsAllowed: (
       parent: HouseRules,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+    ) => boolean | null | Promise<boolean | null>;
 
     smokingAllowed: (
       parent: HouseRules,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+    ) => boolean | null | Promise<boolean | null>;
 
     suitableForChildren: (
       parent: HouseRules,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+    ) => boolean | null | Promise<boolean | null>;
 
     suitableForInfants: (
       parent: HouseRules,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => boolean | null | undefined | Promise<boolean | null | undefined>;
+    ) => boolean | null | Promise<boolean | null>;
 
     updatedAt: (
       parent: HouseRules,
@@ -3283,11 +3239,7 @@ export namespace PaymentAccountResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | PAYMENT_PROVIDER
-      | null
-      | undefined
-      | Promise<PAYMENT_PROVIDER | null | undefined>;
+    ) => PAYMENT_PROVIDER | null | Promise<PAYMENT_PROVIDER | null>;
 
     user: (
       parent: PaymentAccount,
@@ -3308,22 +3260,14 @@ export namespace PaymentAccountResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | PaypalInformation
-      | null
-      | undefined
-      | Promise<PaypalInformation | null | undefined>;
+    ) => PaypalInformation | null | Promise<PaypalInformation | null>;
 
     creditcard: (
       parent: PaymentAccount,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | CreditCardInformation
-      | null
-      | undefined
-      | Promise<CreditCardInformation | null | undefined>;
+    ) => CreditCardInformation | null | Promise<CreditCardInformation | null>;
   }
 }
 
@@ -3549,11 +3493,7 @@ export namespace CreditCardInformationResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | PaymentAccount
-      | null
-      | undefined
-      | Promise<PaymentAccount | null | undefined>;
+    ) => PaymentAccount | null | Promise<PaymentAccount | null>;
 
     postalCode: (
       parent: CreditCardInformation,
@@ -3658,11 +3598,7 @@ export namespace NotificationResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) =>
-      | NOTIFICATION_TYPE
-      | null
-      | undefined
-      | Promise<NOTIFICATION_TYPE | null | undefined>;
+    ) => NOTIFICATION_TYPE | null | Promise<NOTIFICATION_TYPE | null>;
 
     user: (
       parent: Notification,

From 825054fc1d2009589b7ecdd7cd21eeeb83475393 Mon Sep 17 00:00:00 2001
From: Jason Kuhrt <jasonkuhrt@me.com>
Date: Wed, 2 Jan 2019 23:13:19 -0500
Subject: [PATCH 5/8] void is not possible within array members

---
 packages/graphqlgen/src/generators/common.ts  | 55 ++++++++++++-------
 .../__snapshots__/basic.test.ts.snap          |  4 +-
 2 files changed, 38 insertions(+), 21 deletions(-)

diff --git a/packages/graphqlgen/src/generators/common.ts b/packages/graphqlgen/src/generators/common.ts
index bf781ac4..a00fd0c7 100644
--- a/packages/graphqlgen/src/generators/common.ts
+++ b/packages/graphqlgen/src/generators/common.ts
@@ -188,33 +188,50 @@ export function shouldScaffoldFieldResolver(
   return !shouldRenderDefaultResolver(graphQLField, modelField, args)
 }
 
-export function printFieldLikeType(
+const voidable = (type: string): string => {
+  return `${type} | null | undefined`
+}
+
+const nullable = (type: string): string => {
+  return `${type} | null`
+}
+
+export const printFieldLikeType = (
   field: GraphQLTypeField,
   modelMap: ModelMap,
-) {
+): string => {
   const name = field.type.isScalar
     ? getTypeFromGraphQLType(field.type.name)
     : field.type.isInput || field.type.isEnum
     ? field.type.name
     : getModelName(field.type, modelMap)
 
-  const isRequired = field.type.isArray
-    ? field.type.isArrayRequired
-    : field.type.isRequired
-
-  const suffix = isRequired
-    ? ''
-    : field.defaultValue === null
-    ? ' | null'
-    : field.defaultValue === undefined
-    ? ' | null | undefined'
-    : ''
-
-  const type = field.type.isArray
-    ? name + (field.type.isRequired ? '' : ' | null | undefined')
-    : name + suffix
-
-  return field.type.isArray ? `Array<${type}>${suffix}` : type
+  if (field.type.isArray) {
+    // A void array member is not possible
+    const innerTypeRendering = field.type.isRequired ? name : nullable(name)
+
+    const typeRendering = field.type.isArrayRequired
+      ? `Array<${innerTypeRendering}>`
+      : field.defaultValue === null
+      ? nullable(`Array<${innerTypeRendering}>`)
+      : field.defaultValue === undefined
+      ? voidable(`Array<${innerTypeRendering}>`)
+      : // field.defaultValue has has been set to non-null in the schema
+        `Array<${innerTypeRendering}>`
+
+    return typeRendering
+  } else {
+    const typeRendering = field.type.isRequired
+      ? name
+      : field.defaultValue === null
+      ? nullable(name)
+      : field.defaultValue === undefined
+      ? voidable(name)
+      : // field.defaultValue has has been set to non-null in the schema
+        name
+
+    return typeRendering
+  }
 }
 
 export function printFieldLikeFlowType(
diff --git a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
index a98aa78e..312f5d45 100644
--- a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
+++ b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
@@ -176,9 +176,9 @@ export namespace MutationResolvers {
   export interface AddMemberData {
     email: string;
     projects: Array<string>;
-    sideProjects: Array<string | null | undefined> | null | undefined;
+    sideProjects: Array<string | null> | null | undefined;
     profile: ProfileData | null;
-    phones: Array<PhoneData | null | undefined>;
+    phones: Array<PhoneData | null>;
     isVIP: boolean;
   }
   export interface ProfileData {

From ec94881318a5074c3f8c2f18b1819e0d5ef9e8c3 Mon Sep 17 00:00:00 2001
From: Jason Kuhrt <jasonkuhrt@me.com>
Date: Wed, 2 Jan 2019 23:23:42 -0500
Subject: [PATCH 6/8] refactor

---
 packages/graphqlgen/src/generators/common.ts  | 82 +++++--------------
 .../src/generators/flow-generator.ts          | 21 +++--
 .../graphqlgen/src/generators/ts-generator.ts |  5 +-
 3 files changed, 37 insertions(+), 71 deletions(-)

diff --git a/packages/graphqlgen/src/generators/common.ts b/packages/graphqlgen/src/generators/common.ts
index a00fd0c7..ee507fae 100644
--- a/packages/graphqlgen/src/generators/common.ts
+++ b/packages/graphqlgen/src/generators/common.ts
@@ -188,8 +188,9 @@ export function shouldScaffoldFieldResolver(
   return !shouldRenderDefaultResolver(graphQLField, modelField, args)
 }
 
-const voidable = (type: string): string => {
-  return `${type} | null | undefined`
+const voidable = (type: string, isFlowtype: boolean = false): string => {
+  const voidType = isFlowtype ? 'void' : 'undefined'
+  return `${type} | null | ${voidType}`
 }
 
 const nullable = (type: string): string => {
@@ -199,6 +200,13 @@ const nullable = (type: string): string => {
 export const printFieldLikeType = (
   field: GraphQLTypeField,
   modelMap: ModelMap,
+  options: {
+    isReturn?: boolean
+    isFlowtype?: boolean
+  } = {
+    isReturn: false,
+    isFlowtype: false,
+  },
 ): string => {
   const name = field.type.isScalar
     ? getTypeFromGraphQLType(field.type.name)
@@ -215,7 +223,11 @@ export const printFieldLikeType = (
       : field.defaultValue === null
       ? nullable(`Array<${innerTypeRendering}>`)
       : field.defaultValue === undefined
-      ? voidable(`Array<${innerTypeRendering}>`)
+      ? // return type doesn't permit void return since that would allow
+        // resolvers to e.g. forget to return anything and that be considered OK.
+        options.isReturn
+        ? nullable(`Array<${innerTypeRendering}>`)
+        : voidable(`Array<${innerTypeRendering}>`, options.isFlowtype)
       : // field.defaultValue has has been set to non-null in the schema
         `Array<${innerTypeRendering}>`
 
@@ -226,7 +238,11 @@ export const printFieldLikeType = (
       : field.defaultValue === null
       ? nullable(name)
       : field.defaultValue === undefined
-      ? voidable(name)
+      ? // return type doesn't permit void return since that would allow
+        // resolvers to e.g. forget to return anything and that be considered OK.
+        options.isReturn
+        ? nullable(name)
+        : voidable(name, options.isFlowtype)
       : // field.defaultValue has has been set to non-null in the schema
         name
 
@@ -234,64 +250,6 @@ export const printFieldLikeType = (
   }
 }
 
-export function printFieldLikeFlowType(
-  field: GraphQLTypeField,
-  modelMap: ModelMap,
-) {
-  const name = field.type.isScalar
-    ? getTypeFromGraphQLType(field.type.name)
-    : field.type.isInput || field.type.isEnum
-    ? field.type.name
-    : getModelName(field.type, modelMap)
-
-  const isRequired = field.type.isArray
-    ? field.type.isArrayRequired
-    : field.type.isRequired
-
-  const suffix = isRequired
-    ? ''
-    : field.defaultValue === null
-    ? ' | null'
-    : field.defaultValue === undefined
-    ? ' | null | void'
-    : ''
-
-  const type = field.type.isArray
-    ? name + (field.type.isRequired ? '' : ' | null | void')
-    : name + suffix
-
-  return field.type.isArray ? `Array<${type}>${suffix}` : type
-}
-
-export function printFieldLikeReturnType(
-  field: GraphQLTypeField,
-  modelMap: ModelMap,
-) {
-  const name = field.type.isScalar
-    ? getTypeFromGraphQLType(field.type.name)
-    : field.type.isInput || field.type.isEnum
-    ? field.type.name
-    : getModelName(field.type, modelMap)
-
-  const isRequired = field.type.isArray
-    ? field.type.isArrayRequired
-    : field.type.isRequired
-
-  const suffix = isRequired
-    ? ''
-    : field.defaultValue === null
-    ? ' | null'
-    : field.defaultValue === undefined
-    ? ' | null'
-    : ''
-
-  const type = field.type.isArray
-    ? name + (field.type.isRequired ? '' : ' | null')
-    : name + suffix
-
-  return field.type.isArray ? `Array<${type}>${suffix}` : type
-}
-
 export function getTypeFromGraphQLType(
   type: string,
 ): SpecificGraphQLScalarType {
diff --git a/packages/graphqlgen/src/generators/flow-generator.ts b/packages/graphqlgen/src/generators/flow-generator.ts
index 1d05495d..bacdd4af 100644
--- a/packages/graphqlgen/src/generators/flow-generator.ts
+++ b/packages/graphqlgen/src/generators/flow-generator.ts
@@ -14,8 +14,7 @@ import {
   getModelName,
   groupModelsNameByImportPath,
   InputTypesMap,
-  printFieldLikeFlowType,
-  printFieldLikeReturnType,
+  printFieldLikeType,
   renderDefaultResolvers,
   renderEnums,
   TypeToInputTypeAssociation,
@@ -172,7 +171,10 @@ function renderInputTypeInterfaces(
         inputTypesMap[typeAssociation].name,
       )} {
       ${inputTypesMap[typeAssociation].fields.map(
-        field => `${field.name}: ${printFieldLikeFlowType(field, modelMap)}`,
+        field =>
+          `${field.name}: ${printFieldLikeType(field, modelMap, {
+            isFlowtype: true,
+          })}`,
       )}
     }`
     })
@@ -202,9 +204,10 @@ function renderInputArgInterface(
     ${field.arguments
       .map(
         arg =>
-          `${arg.name}: ${getArgTypePrefix(type, arg)}${printFieldLikeFlowType(
+          `${arg.name}: ${getArgTypePrefix(type, arg)}${printFieldLikeType(
             arg as GraphQLTypeField,
             modelMap,
+            { isFlowtype: true },
           )}`,
       )
       .join(',' + os.EOL)}
@@ -256,7 +259,10 @@ function renderResolverFunctionInterface(
   )
   `
 
-  const returnType = printFieldLikeReturnType(field, modelMap)
+  const returnType = printFieldLikeType(field, modelMap, {
+    isFlowtype: true,
+    isReturn: true,
+  })
 
   if (type.name === 'Subscription') {
     return `
@@ -301,7 +307,10 @@ function renderResolverTypeInterfaceFunction(
     ctx: ${getContextName(context)},
     info: GraphQLResolveInfo,
   )`
-  const returnType = printFieldLikeReturnType(field, modelMap)
+  const returnType = printFieldLikeType(field, modelMap, {
+    isFlowtype: true,
+    isReturn: true,
+  })
 
   if (type.name === 'Subscription') {
     return `
diff --git a/packages/graphqlgen/src/generators/ts-generator.ts b/packages/graphqlgen/src/generators/ts-generator.ts
index 3f7448ea..f61825d8 100644
--- a/packages/graphqlgen/src/generators/ts-generator.ts
+++ b/packages/graphqlgen/src/generators/ts-generator.ts
@@ -10,7 +10,6 @@ import {
   TypeToInputTypeAssociation,
   InputTypesMap,
   printFieldLikeType,
-  printFieldLikeReturnType,
   getDistinctInputTypes,
   renderEnums,
   groupModelsNameByImportPath,
@@ -265,7 +264,7 @@ function renderResolverFunctionInterface(
   )
   `
 
-  const returnType = printFieldLikeReturnType(field, modelMap)
+  const returnType = printFieldLikeType(field, modelMap, { isReturn: true })
 
   if (type.name === 'Subscription') {
     return `
@@ -313,7 +312,7 @@ function renderResolverTypeInterfaceFunction(
     info: GraphQLResolveInfo,
   )
   `
-  const returnType = printFieldLikeReturnType(field, modelMap)
+  const returnType = printFieldLikeType(field, modelMap, { isReturn: true })
 
   if (type.name === 'Subscription') {
     return `

From b9d714d6f124b97ec8aa12bc2a9d420533b9e932 Mon Sep 17 00:00:00 2001
From: Jason Kuhrt <jasonkuhrt@me.com>
Date: Wed, 2 Jan 2019 23:57:52 -0500
Subject: [PATCH 7/8] more idiomatic array rendering

---
 packages/graphqlgen/src/generators/common.ts  | 36 ++++----
 .../flow/__snapshots__/basic.test.ts.snap     |  2 +-
 .../__snapshots__/large-schema.test.ts.snap   | 90 +++++++++----------
 .../__snapshots__/basic.test.ts.snap          |  6 +-
 .../__snapshots__/large-schema.test.ts.snap   | 90 +++++++++----------
 5 files changed, 115 insertions(+), 109 deletions(-)

diff --git a/packages/graphqlgen/src/generators/common.ts b/packages/graphqlgen/src/generators/common.ts
index ee507fae..6f5f6420 100644
--- a/packages/graphqlgen/src/generators/common.ts
+++ b/packages/graphqlgen/src/generators/common.ts
@@ -197,6 +197,10 @@ const nullable = (type: string): string => {
   return `${type} | null`
 }
 
+const array = (innerType: string, config: { innerUnion?: boolean } = {}) => {
+  return config.innerUnion ? `${innerType}[]` : `Array<${innerType}>`
+}
+
 export const printFieldLikeType = (
   field: GraphQLTypeField,
   modelMap: ModelMap,
@@ -214,22 +218,27 @@ export const printFieldLikeType = (
     ? field.type.name
     : getModelName(field.type, modelMap)
 
+  /**
+   * 1. Return type doesn't permit void return since that would allow
+   *    resolvers to e.g. forget to return anything and that be considered OK.
+   */
   if (field.type.isArray) {
-    // A void array member is not possible
+    const innerUnion = field.type.isRequired
+    // Not voidable here because a void array member is not possible
     const innerTypeRendering = field.type.isRequired ? name : nullable(name)
 
     const typeRendering = field.type.isArrayRequired
-      ? `Array<${innerTypeRendering}>`
+      ? array(innerTypeRendering, { innerUnion })
       : field.defaultValue === null
-      ? nullable(`Array<${innerTypeRendering}>`)
+      ? nullable(array(innerTypeRendering, { innerUnion }))
       : field.defaultValue === undefined
-      ? // return type doesn't permit void return since that would allow
-        // resolvers to e.g. forget to return anything and that be considered OK.
-        options.isReturn
-        ? nullable(`Array<${innerTypeRendering}>`)
-        : voidable(`Array<${innerTypeRendering}>`, options.isFlowtype)
-      : // field.defaultValue has has been set to non-null in the schema
-        `Array<${innerTypeRendering}>`
+      ? options.isReturn // [1]
+        ? nullable(array(innerTypeRendering, { innerUnion }))
+        : voidable(
+            array(innerTypeRendering, { innerUnion }),
+            options.isFlowtype,
+          )
+      : array(innerTypeRendering, { innerUnion }) // schema has non-null default set
 
     return typeRendering
   } else {
@@ -238,13 +247,10 @@ export const printFieldLikeType = (
       : field.defaultValue === null
       ? nullable(name)
       : field.defaultValue === undefined
-      ? // return type doesn't permit void return since that would allow
-        // resolvers to e.g. forget to return anything and that be considered OK.
-        options.isReturn
+      ? options.isReturn // [1]
         ? nullable(name)
         : voidable(name, options.isFlowtype)
-      : // field.defaultValue has has been set to non-null in the schema
-        name
+      : name // schema has non-null default set
 
     return typeRendering
   }
diff --git a/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap b/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
index 8f2ffc59..c8554af3 100644
--- a/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
+++ b/packages/graphqlgen/src/tests/flow/__snapshots__/basic.test.ts.snap
@@ -172,7 +172,7 @@ export const Mutation_defaultResolvers = {};
 
 export interface Mutation_AddMemberData {
   email: string;
-  projects: Array<string>;
+  projects: string[];
 }
 
 export interface Mutation_Args_AddMember {
diff --git a/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap b/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
index 28b78d34..b3ec0170 100644
--- a/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
+++ b/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
@@ -64,7 +64,7 @@ export interface Query_Args_HomesInPriceRange {
 }
 
 export interface Query_Args_ExperiencesByCity {
-  cities: Array<string>;
+  cities: string[];
 }
 
 export type Query_TopExperiences_Resolver = (
@@ -72,42 +72,42 @@ export type Query_TopExperiences_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Experience> | Promise<Array<Experience>>;
+) => Experience[] | Promise<Experience[]>;
 
 export type Query_TopHomes_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Home> | Promise<Array<Home>>;
+) => Home[] | Promise<Home[]>;
 
 export type Query_HomesInPriceRange_Resolver = (
   parent: {},
   args: Query_Args_HomesInPriceRange,
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Home> | Promise<Array<Home>>;
+) => Home[] | Promise<Home[]>;
 
 export type Query_TopReservations_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Reservation> | Promise<Array<Reservation>>;
+) => Reservation[] | Promise<Reservation[]>;
 
 export type Query_FeaturedDestinations_Resolver = (
   parent: {},
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Neighbourhood> | Promise<Array<Neighbourhood>>;
+) => Neighbourhood[] | Promise<Neighbourhood[]>;
 
 export type Query_ExperiencesByCity_Resolver = (
   parent: {},
   args: Query_Args_ExperiencesByCity,
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<ExperiencesByCity> | Promise<Array<ExperiencesByCity>>;
+) => ExperiencesByCity[] | Promise<ExperiencesByCity[]>;
 
 export type Query_Viewer_Resolver = (
   parent: {},
@@ -129,42 +129,42 @@ export interface Query_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Experience> | Promise<Array<Experience>>;
+  ) => Experience[] | Promise<Experience[]>;
 
   topHomes: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Home> | Promise<Array<Home>>;
+  ) => Home[] | Promise<Home[]>;
 
   homesInPriceRange: (
     parent: {},
     args: Query_Args_HomesInPriceRange,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Home> | Promise<Array<Home>>;
+  ) => Home[] | Promise<Home[]>;
 
   topReservations: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Reservation> | Promise<Array<Reservation>>;
+  ) => Reservation[] | Promise<Reservation[]>;
 
   featuredDestinations: (
     parent: {},
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Neighbourhood> | Promise<Array<Neighbourhood>>;
+  ) => Neighbourhood[] | Promise<Neighbourhood[]>;
 
   experiencesByCity: (
     parent: {},
     args: Query_Args_ExperiencesByCity,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<ExperiencesByCity> | Promise<Array<ExperiencesByCity>>;
+  ) => ExperiencesByCity[] | Promise<ExperiencesByCity[]>;
 
   viewer: (
     parent: {},
@@ -234,7 +234,7 @@ export type Experience_Reviews_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Review> | Promise<Array<Review>>;
+) => Review[] | Promise<Review[]>;
 
 export type Experience_Preview_Resolver = (
   parent: Experience,
@@ -291,7 +291,7 @@ export interface Experience_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Review> | Promise<Array<Review>>;
+  ) => Review[] | Promise<Review[]>;
 
   preview: (
     parent: Experience,
@@ -706,7 +706,7 @@ export type Home_Pictures_Resolver = (
   args: Home_Args_Pictures,
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Picture> | Promise<Array<Picture>>;
+) => Picture[] | Promise<Picture[]>;
 
 export type Home_PerNight_Resolver = (
   parent: Home,
@@ -756,7 +756,7 @@ export interface Home_Resolvers {
     args: Home_Args_Pictures,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Picture> | Promise<Array<Picture>>;
+  ) => Picture[] | Promise<Picture[]>;
 
   perNight: (
     parent: Home,
@@ -804,7 +804,7 @@ export type Reservation_Pictures_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Picture> | Promise<Array<Picture>>;
+) => Picture[] | Promise<Picture[]>;
 
 export type Reservation_Location_Resolver = (
   parent: Reservation,
@@ -861,7 +861,7 @@ export interface Reservation_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Picture> | Promise<Array<Picture>>;
+  ) => Picture[] | Promise<Picture[]>;
 
   location: (
     parent: Reservation,
@@ -1051,7 +1051,7 @@ export type ExperiencesByCity_Experiences_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Experience> | Promise<Array<Experience>>;
+) => Experience[] | Promise<Experience[]>;
 
 export type ExperiencesByCity_City_Resolver = (
   parent: ExperiencesByCity,
@@ -1066,7 +1066,7 @@ export interface ExperiencesByCity_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Experience> | Promise<Array<Experience>>;
+  ) => Experience[] | Promise<Experience[]>;
 
   city: (
     parent: ExperiencesByCity,
@@ -1094,7 +1094,7 @@ export type Viewer_Bookings_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Booking> | Promise<Array<Booking>>;
+) => Booking[] | Promise<Booking[]>;
 
 export interface Viewer_Resolvers {
   me: (
@@ -1109,7 +1109,7 @@ export interface Viewer_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Booking> | Promise<Array<Booking>>;
+  ) => Booking[] | Promise<Booking[]>;
 }
 
 // Types for User
@@ -1141,7 +1141,7 @@ export type User_Bookings_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Booking> | null | Promise<Array<Booking> | null>;
+) => Booking[] | null | Promise<Booking[] | null>;
 
 export type User_CreatedAt_Resolver = (
   parent: User,
@@ -1169,7 +1169,7 @@ export type User_HostingExperiences_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Experience> | null | Promise<Array<Experience> | null>;
+) => Experience[] | null | Promise<Experience[] | null>;
 
 export type User_Id_Resolver = (
   parent: User,
@@ -1204,21 +1204,21 @@ export type User_Notifications_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Notification> | null | Promise<Array<Notification> | null>;
+) => Notification[] | null | Promise<Notification[] | null>;
 
 export type User_OwnedPlaces_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Place> | null | Promise<Array<Place> | null>;
+) => Place[] | null | Promise<Place[] | null>;
 
 export type User_PaymentAccount_Resolver = (
   parent: User,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<PaymentAccount> | null | Promise<Array<PaymentAccount> | null>;
+) => PaymentAccount[] | null | Promise<PaymentAccount[] | null>;
 
 export type User_Phone_Resolver = (
   parent: User,
@@ -1239,7 +1239,7 @@ export type User_ReceivedMessages_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Message> | null | Promise<Array<Message> | null>;
+) => Message[] | null | Promise<Message[] | null>;
 
 export type User_ResponseRate_Resolver = (
   parent: User,
@@ -1260,7 +1260,7 @@ export type User_SentMessages_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Message> | null | Promise<Array<Message> | null>;
+) => Message[] | null | Promise<Message[] | null>;
 
 export type User_UpdatedAt_Resolver = (
   parent: User,
@@ -1282,7 +1282,7 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Booking> | null | Promise<Array<Booking> | null>;
+  ) => Booking[] | null | Promise<Booking[] | null>;
 
   createdAt: (
     parent: User,
@@ -1310,7 +1310,7 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Experience> | null | Promise<Array<Experience> | null>;
+  ) => Experience[] | null | Promise<Experience[] | null>;
 
   id: (
     parent: User,
@@ -1345,21 +1345,21 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Notification> | null | Promise<Array<Notification> | null>;
+  ) => Notification[] | null | Promise<Notification[] | null>;
 
   ownedPlaces: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Place> | null | Promise<Array<Place> | null>;
+  ) => Place[] | null | Promise<Place[] | null>;
 
   paymentAccount: (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<PaymentAccount> | null | Promise<Array<PaymentAccount> | null>;
+  ) => PaymentAccount[] | null | Promise<PaymentAccount[] | null>;
 
   phone: (
     parent: User,
@@ -1380,7 +1380,7 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Message> | null | Promise<Array<Message> | null>;
+  ) => Message[] | null | Promise<Message[] | null>;
 
   responseRate: (
     parent: User,
@@ -1401,7 +1401,7 @@ export interface User_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Message> | null | Promise<Array<Message> | null>;
+  ) => Message[] | null | Promise<Message[] | null>;
 
   updatedAt: (
     parent: User,
@@ -1633,7 +1633,7 @@ export type Place_Reviews_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Review> | Promise<Array<Review>>;
+) => Review[] | Promise<Review[]>;
 
 export type Place_Amenities_Resolver = (
   parent: Place,
@@ -1696,14 +1696,14 @@ export type Place_Bookings_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Booking> | Promise<Array<Booking>>;
+) => Booking[] | Promise<Booking[]>;
 
 export type Place_Pictures_Resolver = (
   parent: Place,
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Picture> | null | Promise<Array<Picture> | null>;
+) => Picture[] | null | Promise<Picture[] | null>;
 
 export type Place_Popularity_Resolver = (
   parent: Place,
@@ -1788,7 +1788,7 @@ export interface Place_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Review> | Promise<Array<Review>>;
+  ) => Review[] | Promise<Review[]>;
 
   amenities: (
     parent: Place,
@@ -1851,14 +1851,14 @@ export interface Place_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Booking> | Promise<Array<Booking>>;
+  ) => Booking[] | Promise<Booking[]>;
 
   pictures: (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Picture> | null | Promise<Array<Picture> | null>;
+  ) => Picture[] | null | Promise<Picture[] | null>;
 
   popularity: (
     parent: Place,
@@ -3178,7 +3178,7 @@ export type PaymentAccount_Payments_Resolver = (
   args: {},
   ctx: Context,
   info: GraphQLResolveInfo
-) => Array<Payment> | Promise<Array<Payment>>;
+) => Payment[] | Promise<Payment[]>;
 
 export type PaymentAccount_Paypal_Resolver = (
   parent: PaymentAccount,
@@ -3228,7 +3228,7 @@ export interface PaymentAccount_Resolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Payment> | Promise<Array<Payment>>;
+  ) => Payment[] | Promise<Payment[]>;
 
   paypal: (
     parent: PaymentAccount,
diff --git a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
index 312f5d45..01cd59ce 100644
--- a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
+++ b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
@@ -175,7 +175,7 @@ export namespace MutationResolvers {
 
   export interface AddMemberData {
     email: string;
-    projects: Array<string>;
+    projects: string[];
     sideProjects: Array<string | null> | null | undefined;
     profile: ProfileData | null;
     phones: Array<PhoneData | null>;
@@ -201,7 +201,7 @@ export namespace MutationResolvers {
   }
 
   export interface ArgsAddMembers {
-    data: Array<AddMemberData>;
+    data: AddMemberData[];
   }
 
   export type AddMemberResolver = (
@@ -348,7 +348,7 @@ export namespace MutationResolvers {
 
   export interface AddMemberData {
     email: string;
-    projects: Array<string>;
+    projects: string[];
   }
 
   export interface ArgsAddMember {
diff --git a/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap b/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
index 129c286c..304d7ed3 100644
--- a/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
+++ b/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
@@ -63,7 +63,7 @@ export namespace QueryResolvers {
   }
 
   export interface ArgsExperiencesByCity {
-    cities: Array<string>;
+    cities: string[];
   }
 
   export type TopExperiencesResolver = (
@@ -71,42 +71,42 @@ export namespace QueryResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Experience> | Promise<Array<Experience>>;
+  ) => Experience[] | Promise<Experience[]>;
 
   export type TopHomesResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Home> | Promise<Array<Home>>;
+  ) => Home[] | Promise<Home[]>;
 
   export type HomesInPriceRangeResolver = (
     parent: undefined,
     args: ArgsHomesInPriceRange,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Home> | Promise<Array<Home>>;
+  ) => Home[] | Promise<Home[]>;
 
   export type TopReservationsResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Reservation> | Promise<Array<Reservation>>;
+  ) => Reservation[] | Promise<Reservation[]>;
 
   export type FeaturedDestinationsResolver = (
     parent: undefined,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Neighbourhood> | Promise<Array<Neighbourhood>>;
+  ) => Neighbourhood[] | Promise<Neighbourhood[]>;
 
   export type ExperiencesByCityResolver = (
     parent: undefined,
     args: ArgsExperiencesByCity,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<ExperiencesByCity> | Promise<Array<ExperiencesByCity>>;
+  ) => ExperiencesByCity[] | Promise<ExperiencesByCity[]>;
 
   export type ViewerResolver = (
     parent: undefined,
@@ -128,42 +128,42 @@ export namespace QueryResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Experience> | Promise<Array<Experience>>;
+    ) => Experience[] | Promise<Experience[]>;
 
     topHomes: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Home> | Promise<Array<Home>>;
+    ) => Home[] | Promise<Home[]>;
 
     homesInPriceRange: (
       parent: undefined,
       args: ArgsHomesInPriceRange,
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Home> | Promise<Array<Home>>;
+    ) => Home[] | Promise<Home[]>;
 
     topReservations: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Reservation> | Promise<Array<Reservation>>;
+    ) => Reservation[] | Promise<Reservation[]>;
 
     featuredDestinations: (
       parent: undefined,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Neighbourhood> | Promise<Array<Neighbourhood>>;
+    ) => Neighbourhood[] | Promise<Neighbourhood[]>;
 
     experiencesByCity: (
       parent: undefined,
       args: ArgsExperiencesByCity,
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<ExperiencesByCity> | Promise<Array<ExperiencesByCity>>;
+    ) => ExperiencesByCity[] | Promise<ExperiencesByCity[]>;
 
     viewer: (
       parent: undefined,
@@ -234,7 +234,7 @@ export namespace ExperienceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Review> | Promise<Array<Review>>;
+  ) => Review[] | Promise<Review[]>;
 
   export type PreviewResolver = (
     parent: Experience,
@@ -291,7 +291,7 @@ export namespace ExperienceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Review> | Promise<Array<Review>>;
+    ) => Review[] | Promise<Review[]>;
 
     preview: (
       parent: Experience,
@@ -711,7 +711,7 @@ export namespace HomeResolvers {
     args: ArgsPictures,
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Picture> | Promise<Array<Picture>>;
+  ) => Picture[] | Promise<Picture[]>;
 
   export type PerNightResolver = (
     parent: Home,
@@ -761,7 +761,7 @@ export namespace HomeResolvers {
       args: ArgsPictures,
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Picture> | Promise<Array<Picture>>;
+    ) => Picture[] | Promise<Picture[]>;
 
     perNight: (
       parent: Home,
@@ -810,7 +810,7 @@ export namespace ReservationResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Picture> | Promise<Array<Picture>>;
+  ) => Picture[] | Promise<Picture[]>;
 
   export type LocationResolver = (
     parent: Reservation,
@@ -867,7 +867,7 @@ export namespace ReservationResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Picture> | Promise<Array<Picture>>;
+    ) => Picture[] | Promise<Picture[]>;
 
     location: (
       parent: Reservation,
@@ -1060,7 +1060,7 @@ export namespace ExperiencesByCityResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Experience> | Promise<Array<Experience>>;
+  ) => Experience[] | Promise<Experience[]>;
 
   export type CityResolver = (
     parent: ExperiencesByCity,
@@ -1075,7 +1075,7 @@ export namespace ExperiencesByCityResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Experience> | Promise<Array<Experience>>;
+    ) => Experience[] | Promise<Experience[]>;
 
     city: (
       parent: ExperiencesByCity,
@@ -1104,7 +1104,7 @@ export namespace ViewerResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Booking> | Promise<Array<Booking>>;
+  ) => Booking[] | Promise<Booking[]>;
 
   export interface Type {
     me: (
@@ -1119,7 +1119,7 @@ export namespace ViewerResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Booking> | Promise<Array<Booking>>;
+    ) => Booking[] | Promise<Booking[]>;
   }
 }
 
@@ -1152,7 +1152,7 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Booking> | null | Promise<Array<Booking> | null>;
+  ) => Booking[] | null | Promise<Booking[] | null>;
 
   export type CreatedAtResolver = (
     parent: User,
@@ -1180,7 +1180,7 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Experience> | null | Promise<Array<Experience> | null>;
+  ) => Experience[] | null | Promise<Experience[] | null>;
 
   export type IdResolver = (
     parent: User,
@@ -1215,21 +1215,21 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Notification> | null | Promise<Array<Notification> | null>;
+  ) => Notification[] | null | Promise<Notification[] | null>;
 
   export type OwnedPlacesResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Place> | null | Promise<Array<Place> | null>;
+  ) => Place[] | null | Promise<Place[] | null>;
 
   export type PaymentAccountResolver = (
     parent: User,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<PaymentAccount> | null | Promise<Array<PaymentAccount> | null>;
+  ) => PaymentAccount[] | null | Promise<PaymentAccount[] | null>;
 
   export type PhoneResolver = (
     parent: User,
@@ -1250,7 +1250,7 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Message> | null | Promise<Array<Message> | null>;
+  ) => Message[] | null | Promise<Message[] | null>;
 
   export type ResponseRateResolver = (
     parent: User,
@@ -1271,7 +1271,7 @@ export namespace UserResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Message> | null | Promise<Array<Message> | null>;
+  ) => Message[] | null | Promise<Message[] | null>;
 
   export type UpdatedAtResolver = (
     parent: User,
@@ -1293,7 +1293,7 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Booking> | null | Promise<Array<Booking> | null>;
+    ) => Booking[] | null | Promise<Booking[] | null>;
 
     createdAt: (
       parent: User,
@@ -1321,7 +1321,7 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Experience> | null | Promise<Array<Experience> | null>;
+    ) => Experience[] | null | Promise<Experience[] | null>;
 
     id: (
       parent: User,
@@ -1356,21 +1356,21 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Notification> | null | Promise<Array<Notification> | null>;
+    ) => Notification[] | null | Promise<Notification[] | null>;
 
     ownedPlaces: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Place> | null | Promise<Array<Place> | null>;
+    ) => Place[] | null | Promise<Place[] | null>;
 
     paymentAccount: (
       parent: User,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<PaymentAccount> | null | Promise<Array<PaymentAccount> | null>;
+    ) => PaymentAccount[] | null | Promise<PaymentAccount[] | null>;
 
     phone: (
       parent: User,
@@ -1391,7 +1391,7 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Message> | null | Promise<Array<Message> | null>;
+    ) => Message[] | null | Promise<Message[] | null>;
 
     responseRate: (
       parent: User,
@@ -1412,7 +1412,7 @@ export namespace UserResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Message> | null | Promise<Array<Message> | null>;
+    ) => Message[] | null | Promise<Message[] | null>;
 
     updatedAt: (
       parent: User,
@@ -1646,7 +1646,7 @@ export namespace PlaceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Review> | Promise<Array<Review>>;
+  ) => Review[] | Promise<Review[]>;
 
   export type AmenitiesResolver = (
     parent: Place,
@@ -1709,14 +1709,14 @@ export namespace PlaceResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Booking> | Promise<Array<Booking>>;
+  ) => Booking[] | Promise<Booking[]>;
 
   export type PicturesResolver = (
     parent: Place,
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Picture> | null | Promise<Array<Picture> | null>;
+  ) => Picture[] | null | Promise<Picture[] | null>;
 
   export type PopularityResolver = (
     parent: Place,
@@ -1801,7 +1801,7 @@ export namespace PlaceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Review> | Promise<Array<Review>>;
+    ) => Review[] | Promise<Review[]>;
 
     amenities: (
       parent: Place,
@@ -1864,14 +1864,14 @@ export namespace PlaceResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Booking> | Promise<Array<Booking>>;
+    ) => Booking[] | Promise<Booking[]>;
 
     pictures: (
       parent: Place,
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Picture> | null | Promise<Array<Picture> | null>;
+    ) => Picture[] | null | Promise<Picture[] | null>;
 
     popularity: (
       parent: Place,
@@ -3203,7 +3203,7 @@ export namespace PaymentAccountResolvers {
     args: {},
     ctx: Context,
     info: GraphQLResolveInfo
-  ) => Array<Payment> | Promise<Array<Payment>>;
+  ) => Payment[] | Promise<Payment[]>;
 
   export type PaypalResolver = (
     parent: PaymentAccount,
@@ -3253,7 +3253,7 @@ export namespace PaymentAccountResolvers {
       args: {},
       ctx: Context,
       info: GraphQLResolveInfo
-    ) => Array<Payment> | Promise<Array<Payment>>;
+    ) => Payment[] | Promise<Payment[]>;
 
     paypal: (
       parent: PaymentAccount,

From 7093f56d4bccfd2bd92228b1b79163be3cf3a353 Mon Sep 17 00:00:00 2001
From: Jason Kuhrt <jasonkuhrt@me.com>
Date: Fri, 4 Jan 2019 22:33:10 -0500
Subject: [PATCH 8/8] mark fields as possibly not there instead of union void

---
 packages/graphqlgen/src/generators/common.ts  | 92 +++++++++++--------
 .../src/generators/flow-generator.ts          | 21 ++---
 .../graphqlgen/src/generators/ts-generator.ts | 12 +--
 .../__snapshots__/large-schema.test.ts.snap   |  2 +-
 .../__snapshots__/basic.test.ts.snap          |  8 +-
 .../__snapshots__/large-schema.test.ts.snap   |  2 +-
 6 files changed, 70 insertions(+), 67 deletions(-)

diff --git a/packages/graphqlgen/src/generators/common.ts b/packages/graphqlgen/src/generators/common.ts
index 6f5f6420..6b9cea88 100644
--- a/packages/graphqlgen/src/generators/common.ts
+++ b/packages/graphqlgen/src/generators/common.ts
@@ -188,28 +188,31 @@ export function shouldScaffoldFieldResolver(
   return !shouldRenderDefaultResolver(graphQLField, modelField, args)
 }
 
-const voidable = (type: string, isFlowtype: boolean = false): string => {
-  const voidType = isFlowtype ? 'void' : 'undefined'
-  return `${type} | null | ${voidType}`
-}
-
 const nullable = (type: string): string => {
   return `${type} | null`
 }
 
+const kv = (
+  key: string,
+  value: string,
+  isOptional: boolean = false,
+): string => {
+  return `${key}${isOptional ? '?' : ''}: ${value}`
+}
+
 const array = (innerType: string, config: { innerUnion?: boolean } = {}) => {
   return config.innerUnion ? `${innerType}[]` : `Array<${innerType}>`
 }
 
+type FieldPrintOptions = {
+  isReturn?: boolean
+}
+
 export const printFieldLikeType = (
   field: GraphQLTypeField,
   modelMap: ModelMap,
-  options: {
-    isReturn?: boolean
-    isFlowtype?: boolean
-  } = {
+  options: FieldPrintOptions = {
     isReturn: false,
-    isFlowtype: false,
   },
 ): string => {
   const name = field.type.isScalar
@@ -219,40 +222,53 @@ export const printFieldLikeType = (
     : getModelName(field.type, modelMap)
 
   /**
+   * Considerable difference between types in array versus not, such as what
+   * default value means, isRequired, ..., lead to forking the rendering paths.
+   *
+   * Regarding voidable, note how it can only show up in the k:v rendering e.g.:
+   *
+   *     foo?: null | string
+   *
+   * but not for return style e.g.:
+   *
+   *     undefined | null | string
+   *
+   * given footnote 1 below.
+   *
    * 1. Return type doesn't permit void return since that would allow
    *    resolvers to e.g. forget to return anything and that be considered OK.
    */
+
   if (field.type.isArray) {
     const innerUnion = field.type.isRequired
-    // Not voidable here because a void array member is not possible
-    const innerTypeRendering = field.type.isRequired ? name : nullable(name)
-
-    const typeRendering = field.type.isArrayRequired
-      ? array(innerTypeRendering, { innerUnion })
-      : field.defaultValue === null
-      ? nullable(array(innerTypeRendering, { innerUnion }))
-      : field.defaultValue === undefined
-      ? options.isReturn // [1]
-        ? nullable(array(innerTypeRendering, { innerUnion }))
-        : voidable(
-            array(innerTypeRendering, { innerUnion }),
-            options.isFlowtype,
-          )
-      : array(innerTypeRendering, { innerUnion }) // schema has non-null default set
-
-    return typeRendering
+
+    // - Not voidable here because a void array member is not possible
+    // - For arrays default value does not apply to inner value
+    const valueInnerType = field.type.isRequired ? name : nullable(name)
+
+    const isArrayNullable =
+      !field.type.isArrayRequired &&
+      (field.defaultValue === undefined || field.defaultValue === null)
+
+    const isArrayVoidable = isArrayNullable && field.defaultValue === undefined
+
+    const valueType = isArrayNullable
+      ? nullable(array(valueInnerType, { innerUnion })) // [1]
+      : array(valueInnerType, { innerUnion })
+
+    return options.isReturn
+      ? valueType
+      : kv(field.name, valueType, isArrayVoidable)
   } else {
-    const typeRendering = field.type.isRequired
-      ? name
-      : field.defaultValue === null
-      ? nullable(name)
-      : field.defaultValue === undefined
-      ? options.isReturn // [1]
-        ? nullable(name)
-        : voidable(name, options.isFlowtype)
-      : name // schema has non-null default set
-
-    return typeRendering
+    const isNullable =
+      !field.type.isRequired &&
+      (field.defaultValue === undefined || field.defaultValue === null)
+
+    const isVoidable = isNullable && field.defaultValue === undefined
+
+    const valueType = isNullable ? nullable(name) : name // [1]
+
+    return options.isReturn ? valueType : kv(field.name, valueType, isVoidable)
   }
 }
 
diff --git a/packages/graphqlgen/src/generators/flow-generator.ts b/packages/graphqlgen/src/generators/flow-generator.ts
index bacdd4af..fed9c3bf 100644
--- a/packages/graphqlgen/src/generators/flow-generator.ts
+++ b/packages/graphqlgen/src/generators/flow-generator.ts
@@ -170,11 +170,8 @@ function renderInputTypeInterfaces(
       return `export interface ${upperFirst(type.name)}_${upperFirst(
         inputTypesMap[typeAssociation].name,
       )} {
-      ${inputTypesMap[typeAssociation].fields.map(
-        field =>
-          `${field.name}: ${printFieldLikeType(field, modelMap, {
-            isFlowtype: true,
-          })}`,
+      ${inputTypesMap[typeAssociation].fields.map(field =>
+        printFieldLikeType(field, modelMap),
       )}
     }`
     })
@@ -202,13 +199,11 @@ function renderInputArgInterface(
   return `
   export interface ${getInputArgName(type, field)} {
     ${field.arguments
-      .map(
-        arg =>
-          `${arg.name}: ${getArgTypePrefix(type, arg)}${printFieldLikeType(
-            arg as GraphQLTypeField,
-            modelMap,
-            { isFlowtype: true },
-          )}`,
+      .map(arg =>
+        printFieldLikeType(arg as GraphQLTypeField, modelMap).replace(
+          ': ',
+          `: ${getArgTypePrefix(type, arg)}`,
+        ),
       )
       .join(',' + os.EOL)}
   }
@@ -260,7 +255,6 @@ function renderResolverFunctionInterface(
   `
 
   const returnType = printFieldLikeType(field, modelMap, {
-    isFlowtype: true,
     isReturn: true,
   })
 
@@ -308,7 +302,6 @@ function renderResolverTypeInterfaceFunction(
     info: GraphQLResolveInfo,
   )`
   const returnType = printFieldLikeType(field, modelMap, {
-    isFlowtype: true,
     isReturn: true,
   })
 
diff --git a/packages/graphqlgen/src/generators/ts-generator.ts b/packages/graphqlgen/src/generators/ts-generator.ts
index f61825d8..ff234d94 100644
--- a/packages/graphqlgen/src/generators/ts-generator.ts
+++ b/packages/graphqlgen/src/generators/ts-generator.ts
@@ -194,8 +194,8 @@ function renderInputTypeInterfaces(
   return getDistinctInputTypes(type, typeToInputTypeAssociation, inputTypesMap)
     .map(typeAssociation => {
       return `export interface ${inputTypesMap[typeAssociation].name} {
-      ${inputTypesMap[typeAssociation].fields.map(
-        field => `${field.name}: ${printFieldLikeType(field, modelMap)}`,
+      ${inputTypesMap[typeAssociation].fields.map(field =>
+        printFieldLikeType(field, modelMap),
       )}
     }`
     })
@@ -222,13 +222,7 @@ function renderInputArgInterface(
   return `
   export interface Args${upperFirst(field.name)} {
     ${field.arguments
-      .map(
-        arg =>
-          `${arg.name}: ${printFieldLikeType(
-            arg as GraphQLTypeField,
-            modelMap,
-          )}`,
-      )
+      .map(arg => printFieldLikeType(arg as GraphQLTypeField, modelMap))
       .join(os.EOL)}
   }
   `
diff --git a/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap b/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
index b3ec0170..1f359f8e 100644
--- a/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
+++ b/packages/graphqlgen/src/tests/flow/__snapshots__/large-schema.test.ts.snap
@@ -663,7 +663,7 @@ export const Home_defaultResolvers = {
 };
 
 export interface Home_Args_Pictures {
-  first: number | null | void;
+  first?: number | null;
 }
 
 export type Home_Id_Resolver = (
diff --git a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
index 01cd59ce..ed59ad95 100644
--- a/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
+++ b/packages/graphqlgen/src/tests/typescript/__snapshots__/basic.test.ts.snap
@@ -176,15 +176,15 @@ export namespace MutationResolvers {
   export interface AddMemberData {
     email: string;
     projects: string[];
-    sideProjects: Array<string | null> | null | undefined;
+    sideProjects?: Array<string | null> | null;
     profile: ProfileData | null;
     phones: Array<PhoneData | null>;
     isVIP: boolean;
   }
   export interface ProfileData {
-    firstName: string | null | undefined;
-    lastName: string | null | undefined;
-    photo: Photo | null | undefined;
+    firstName?: string | null;
+    lastName?: string | null;
+    photo?: Photo | null;
   }
   export interface PhoneData {
     number: string;
diff --git a/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap b/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
index 304d7ed3..2fa30eeb 100644
--- a/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
+++ b/packages/graphqlgen/src/tests/typescript/__snapshots__/large-schema.test.ts.snap
@@ -668,7 +668,7 @@ export namespace HomeResolvers {
   };
 
   export interface ArgsPictures {
-    first: number | null | undefined;
+    first?: number | null;
   }
 
   export type IdResolver = (