PartialOnUndefinedDeep: Fix it incorrectly removing non-optional pr…

…operties when the input type contains an index signature (#764)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

source/internal.d.ts

@@ -2,6 +2,7 @@ import type {Primitive} from './primitive';
 import type {Simplify} from './simplify';
 import type {Trim} from './trim';
 import type {IsAny} from './is-any';
+import type {IsLiteral} from './is-literal';
 import type {UnknownRecord} from './unknown-record';
 import type {IsNever} from './is-never';
 import type {UnknownArray} from './unknown-array';
@@ -357,6 +358,11 @@ IsPrimitive<Object>
 */
 export type IsPrimitive<T> = [T] extends [Primitive] ? true : false;
 
+/**
+Utility type to retrieve only literal keys from type.
+*/
+export type LiteralKeyOf<T> = keyof {[K in keyof T as IsLiteral<K> extends true ? K : never]-?: never};
+
 /**
 Returns the static, fixed-length portion of the given array, excluding variable-length parts.
 

source/partial-on-undefined-deep.d.ts

@@ -1,4 +1,5 @@
-import type {BuiltIns} from './internal';
+import type {IfUnknown} from './if-unknown';
+import type {BuiltIns, LiteralKeyOf} from './internal';
 import type {Merge} from './merge';
 
 /**
@@ -47,8 +48,8 @@ const testSettings: PartialOnUndefinedDeep<Settings> = {
 @category Object
 */
 export type PartialOnUndefinedDeep<T, Options extends PartialOnUndefinedDeepOptions = {}> = T extends Record<any, any> | undefined
-	? {[KeyType in keyof T as undefined extends T[KeyType] ? KeyType : never]?: PartialOnUndefinedDeepValue<T[KeyType], Options>} extends infer U // Make a partial type with all value types accepting undefined (and set them optional)
-		? Merge<{[KeyType in keyof T as KeyType extends keyof U ? never : KeyType]: PartialOnUndefinedDeepValue<T[KeyType], Options>}, U> // Join all remaining keys not treated in U
+	? {[KeyType in keyof T as undefined extends T[KeyType] ? IfUnknown<T[KeyType], never, KeyType> : never]?: PartialOnUndefinedDeepValue<T[KeyType], Options>} extends infer U // Make a partial type with all value types accepting undefined (and set them optional)
+		? Merge<{[KeyType in keyof T as KeyType extends LiteralKeyOf<U> ? never : KeyType]: PartialOnUndefinedDeepValue<T[KeyType], Options>}, U> // Join all remaining keys not treated in U
 		: never // Should not happen
 	: T;
 

test-d/partial-on-undefined-deep.ts

@@ -1,4 +1,4 @@
-import {expectAssignable} from 'tsd';
+import {expectAssignable, expectType} from 'tsd';
 import type {PartialOnUndefinedDeep} from '../index';
 
 type TestingType = {
@@ -22,8 +22,11 @@ type TestingType = {
 	array2: Array<{propertyA: string; propertyB: number | undefined}> | undefined;
 	readonly1: readonly any[] | undefined;
 	readonly2: ReadonlyArray<{propertyA: string; propertyB: number | undefined}> | undefined;
+	readonly readonlyProperty: string | undefined;
 	tuple: ['test1', {propertyA: string; propertyB: number | undefined}] | undefined;
 };
+declare const indexType: {[k: string]: string | undefined; propertyA: string; propertyB: string | undefined};
+declare const indexTypeUnknown: {[k: string]: unknown; propertyA: string; propertyB: number | undefined};
 
 // Default behavior, without recursion into arrays/tuples
 declare const foo: PartialOnUndefinedDeep<TestingType>;
@@ -48,9 +51,15 @@ expectAssignable<{
 	array2?: TestingType['array2'];
 	readonly1?: TestingType['readonly1'];
 	readonly2?: TestingType['readonly2'];
+	readonly readonlyProperty?: TestingType['readonlyProperty'];
 	tuple?: TestingType['tuple'];
 }>(foo);
 
+declare const indexTypeWithoutRecursion: PartialOnUndefinedDeep<typeof indexType>;
+declare const indexTypeUnknownWithoutRecursion: PartialOnUndefinedDeep<typeof indexTypeUnknown>;
+expectType<{[k: string]: string | undefined; propertyA: string; propertyB?: string | undefined}>(indexTypeWithoutRecursion);
+expectType<{[k: string]: unknown; propertyA: string; propertyB?: number | undefined}>(indexTypeUnknownWithoutRecursion);
+
 // With recursion into arrays/tuples activated
 declare const bar: PartialOnUndefinedDeep<TestingType, {recurseIntoArrays: true}>;
 expectAssignable<{
@@ -74,5 +83,11 @@ expectAssignable<{
 	array2?: Array<{propertyA: string; propertyB?: number | undefined}> | undefined;
 	readonly1?: TestingType['readonly1'];
 	readonly2?: ReadonlyArray<{propertyA: string; propertyB?: number | undefined}> | undefined;
+	readonly readonlyProperty?: TestingType['readonlyProperty'];
 	tuple?: ['test1', {propertyA: string; propertyB?: number | undefined}] | undefined;
 }>(bar);
+
+declare const indexTypeWithRecursion: PartialOnUndefinedDeep<typeof indexType, {recurseIntoArrays: true}>;
+declare const indexTypeUnknownWithRecursion: PartialOnUndefinedDeep<typeof indexTypeUnknown, {recurseIntoArrays: true}>;
+expectType<{[k: string]: string | undefined; propertyA: string; propertyB?: string | undefined}>(indexTypeWithRecursion);
+expectType<{[k: string]: unknown; propertyA: string; propertyB?: number | undefined}>(indexTypeUnknownWithRecursion);