Fix constructor type inference for classes with all optional fields, … (

#2890)
Effect-TS · May 31, 2024 · 5745886 · 5745886
1 parent 6801fca
commit 5745886
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Showing 4 changed files with 26 additions and 4 deletions.
diff --git a/.changeset/quiet-lions-smile.md b/.changeset/quiet-lions-smile.md
@@ -0,0 +1,7 @@
+---
+"@effect/schema": patch
+---
+
+Fix constructor type inference for classes with all optional fields, closes #
+
+This fix addresses an issue where TypeScript incorrectly inferred the constructor parameter type as an empty object {} when all class fields were optional. Now, the constructor properly recognizes arguments as objects with optional fields (e.g., { abc?: number, xyz?: number }).
diff --git a/packages/schema/dtslint/Class.ts b/packages/schema/dtslint/Class.ts
@@ -10,6 +10,10 @@ class NoFields extends S.Class<NoFields>("NoFields")({}) {}
 // $ExpectType [props?: void | {}, disableValidation?: boolean | undefined]
 hole<ConstructorParameters<typeof NoFields>>()
 
+new NoFields()
+
+new NoFields({})
+
 // ---------------------------------------------
 // A class with all fields with a default should permit an empty argument in the constructor.
 // ---------------------------------------------
@@ -18,9 +22,13 @@ class AllDefaultedFields extends S.Class<AllDefaultedFields>("AllDefaultedFields
   a: S.String.pipe(S.propertySignature, S.withConstructorDefault(() => ""))
 }) {}
 
-// $ExpectType [props?: void | {}, disableValidation?: boolean | undefined]
+// $ExpectType [props?: void | { readonly a?: string; }, disableValidation?: boolean | undefined]
 hole<ConstructorParameters<typeof AllDefaultedFields>>()
 
+new AllDefaultedFields()
+
+new AllDefaultedFields({})
+
 // ---------------------------------------------
 // test Context
 // ---------------------------------------------

diff --git a/packages/schema/dtslint/Schema.ts b/packages/schema/dtslint/Schema.ts
@@ -2361,6 +2361,13 @@ const make2 = S.Struct({
 // $ExpectType { readonly a?: string; readonly b: number; readonly c?: boolean; }
 hole<Parameters<typeof make2>["0"]>()
 
+const make3 = S.Struct({
+  a: S.withConstructorDefault(S.propertySignature(S.String), () => "")
+}).make
+
+// $ExpectType { readonly a?: string; }
+hole<Parameters<typeof make3>["0"]>()
+
 class AA extends S.Class<AA>("AA")({
   a: S.propertySignature(S.String).pipe(S.withConstructorDefault(() => "")),
   b: S.Number,
@@ -2390,11 +2397,11 @@ S.asSchema(S.Struct({ a: S.optional(S.String).pipe(S.withDefaults({ decoding: ()
 // $ExpectType Struct<{ a: PropertySignature<":", string, never, "?:", string | undefined, true, never>; }>
 S.Struct({ a: S.optional(S.String).pipe(S.withDefaults({ decoding: () => "", constructor: () => "" })) })
 
-const make3 =
+const make4 =
   S.Struct({ a: S.optional(S.String).pipe(S.withDefaults({ decoding: () => "", constructor: () => "" })) }).make
 
 // $ExpectType { readonly a?: string; }
-hole<Parameters<typeof make3>["0"]>()
+hole<Parameters<typeof make4>["0"]>()
 
 // ---------------------------------------------
 // Schema.AsSchema

diff --git a/packages/schema/src/Schema.ts b/packages/schema/src/Schema.ts
@@ -6684,7 +6684,7 @@ export interface Class<Self, Fields extends Struct.Fields, I, R, C, Inherited, P
   extends Schema<Self, Types.Simplify<I>, R>
 {
   new(
-    props: RequiredKeys<C> extends never ? void | {} : Types.Simplify<C>,
+    props: RequiredKeys<C> extends never ? void | Types.Simplify<C> : Types.Simplify<C>,
     disableValidation?: boolean | undefined
   ): Struct.Type<Fields> & Omit<Inherited, keyof Fields> & Proto