fix(transformer): skip design:returntype metadata for getter/setter methods

Getter and setter methods should not have design:returntype metadata according to TypeScript's emitDecoratorMetadata behavior. They should only have design:type and design:paramtypes.

This change:
- Updates enter_method_definition to conditionally emit design:returntype only for regular methods
- Adds comprehensive test case for getter/setter metadata emission
- Ensures compatibility with TypeScript's decorator metadata implementation

Fixes #14493

Author: Dunqing

crates/oxc_transformer/src/decorator/legacy/metadata.rs

@@ -115,14 +115,18 @@ enum EnumType {
 
 pub struct LegacyDecoratorMetadata<'a, 'ctx> {
     ctx: &'ctx TransformCtx<'a>,
-    /// Stack of method metadata arrays, each array contains 3 expressions:
-    /// `[design:type, design:paramtypes, design:returntype]`
+    /// Stack of method metadata arrays.
+    /// Each array contains metadata expressions in order:
+    /// `[design:type, design:paramtypes, design:returntype (optional)]`
+    ///
+    /// Note: `design:returntype` is omitted for getter and setter methods.
     ///
     /// Only the method that needs to be pushed onto a stack is the method metadata,
     /// which should be inserted after all real decorators. However, method parameters
     /// will be processed before the metadata generation, so we need to temporarily store
     /// them in a stack and pop them when in exit_method_definition.
-    method_metadata_stack: SparseStack<[Expression<'a>; 3]>,
+    // method_metadata_stack: SparseStack<[Option<Expression<'a>>; 3]>,
+    method_metadata_stack: SparseStack<[Option<Expression<'a>>; 3]>,
     /// Stack of constructor metadata expressions, each expression
     /// is the `design:paramtypes`.
     ///
@@ -208,16 +212,25 @@ impl<'a> Traverse<'a, TransformState<'a>> for LegacyDecoratorMetadata<'a, '_> {
                 || method.value.params.items.iter().any(|param| !param.decorators.is_empty()));
 
         let metadata = is_decorated.then(|| {
+            // TypeScript only emits `design:returntype` for regular methods,
+            // not for getters or setters.
+            let should_add_return_type = !method.kind.is_get() && !method.kind.is_set();
+
             [
-                self.create_metadata("design:type", Self::global_function(ctx), ctx),
+                Some(self.create_metadata("design:type", Self::global_function(ctx), ctx)),
                 {
                     let serialized_type =
                         self.serialize_parameter_types_of_node(&method.value.params, ctx);
-                    self.create_metadata("design:paramtypes", serialized_type, ctx)
+                    Some(self.create_metadata("design:paramtypes", serialized_type, ctx))
                 },
                 {
-                    let serialized_type = self.serialize_return_type_of_node(&method.value, ctx);
-                    self.create_metadata("design:returntype", serialized_type, ctx)
+                    if should_add_return_type {
+                        let serialized_type =
+                            self.serialize_return_type_of_node(&method.value, ctx);
+                        Some(self.create_metadata("design:returntype", serialized_type, ctx))
+                    } else {
+                        None
+                    }
                 },
             ]
         });
@@ -302,7 +315,7 @@ impl<'a> LegacyDecoratorMetadata<'a, '_> {
         enum_type
     }
 
-    pub fn pop_method_metadata(&mut self) -> Option<[Expression<'a>; 3]> {
+    pub fn pop_method_metadata(&mut self) -> Option<[Option<Expression<'a>>; 3]> {
         self.method_metadata_stack.pop()
     }
 

crates/oxc_transformer/src/decorator/legacy/mod.rs

@@ -999,7 +999,8 @@ impl<'a> LegacyDecorator<'a, '_> {
                     decorations.push(ArrayExpressionElement::from(metadata));
                 }
             } else if let Some(metadata) = self.metadata.pop_method_metadata() {
-                decorations.extend(metadata.map(ArrayExpressionElement::from));
+                decorations
+                    .extend(metadata.into_iter().flatten().map(ArrayExpressionElement::from));
             }
         }
 

tasks/coverage/snapshots/semantic_typescript.snap

@@ -39221,10 +39221,10 @@ Bindings mismatch:
 after transform: ScopeId(0): ["C", "_decorate", "_decorateMetadata", "_method", "_method2", "dec", "method3"]
 rebuilt        : ScopeId(0): ["C", "_decorate", "_decorateMetadata", "_method", "_method2", "method3"]
 Reference flags mismatch for "_method":
-after transform: ReferenceId(39): ReferenceFlags(Read | Write)
+after transform: ReferenceId(34): ReferenceFlags(Read | Write)
 rebuilt        : ReferenceId(2): ReferenceFlags(Write)
 Reference flags mismatch for "_method2":
-after transform: ReferenceId(48): ReferenceFlags(Read | Write)
+after transform: ReferenceId(42): ReferenceFlags(Read | Write)
 rebuilt        : ReferenceId(4): ReferenceFlags(Write)
 Reference symbol mismatch for "dec":
 after transform: SymbolId(0) "dec"
@@ -39267,10 +39267,10 @@ Bindings mismatch:
 after transform: ScopeId(0): ["C", "_decorate", "_decorateMetadata", "_method", "_method2", "dec", "method3"]
 rebuilt        : ScopeId(0): ["C", "_decorate", "_decorateMetadata", "_method", "_method2", "method3"]
 Reference flags mismatch for "_method":
-after transform: ReferenceId(39): ReferenceFlags(Read | Write)
+after transform: ReferenceId(34): ReferenceFlags(Read | Write)
 rebuilt        : ReferenceId(2): ReferenceFlags(Write)
 Reference flags mismatch for "_method2":
-after transform: ReferenceId(48): ReferenceFlags(Read | Write)
+after transform: ReferenceId(42): ReferenceFlags(Read | Write)
 rebuilt        : ReferenceId(4): ReferenceFlags(Write)
 Reference symbol mismatch for "dec":
 after transform: SymbolId(0) "dec"
@@ -39302,13 +39302,13 @@ Symbol span mismatch for "D":
 after transform: SymbolId(3): Span { start: 137, end: 138 }
 rebuilt        : SymbolId(9): Span { start: 0, end: 0 }
 Symbol reference IDs mismatch for "D":
-after transform: SymbolId(3): [ReferenceId(23), ReferenceId(25)]
-rebuilt        : SymbolId(9): [ReferenceId(20), ReferenceId(30), ReferenceId(33)]
+after transform: SymbolId(3): [ReferenceId(21), ReferenceId(23)]
+rebuilt        : SymbolId(9): [ReferenceId(18), ReferenceId(28), ReferenceId(31)]
 Symbol span mismatch for "D":
 after transform: SymbolId(14): Span { start: 0, end: 0 }
 rebuilt        : SymbolId(10): Span { start: 137, end: 138 }
 Symbol reference IDs mismatch for "D":
-after transform: SymbolId(14): [ReferenceId(28)]
+after transform: SymbolId(14): [ReferenceId(26)]
 rebuilt        : SymbolId(10): []
 Reference symbol mismatch for "dec":
 after transform: SymbolId(0) "dec"
@@ -40331,7 +40331,7 @@ Bindings mismatch:
 after transform: ScopeId(0): ["_C", "_decorateMetadata", "_defineProperty", "_get_x", "_method", "_set_x", "_y", "dec"]
 rebuilt        : ScopeId(0): ["_C", "_decorateMetadata", "_defineProperty", "_get_x", "_method", "_set_x", "_y"]
 Symbol reference IDs mismatch for "_decorateMetadata":
-after transform: SymbolId(10): [ReferenceId(24), ReferenceId(25), ReferenceId(26), ReferenceId(28), ReferenceId(29), ReferenceId(30), ReferenceId(32), ReferenceId(34), ReferenceId(35), ReferenceId(37), ReferenceId(39), ReferenceId(41), ReferenceId(42), ReferenceId(43), ReferenceId(45), ReferenceId(46), ReferenceId(47), ReferenceId(49), ReferenceId(51), ReferenceId(52), ReferenceId(54), ReferenceId(56)]
+after transform: SymbolId(10): [ReferenceId(24), ReferenceId(25), ReferenceId(26), ReferenceId(28), ReferenceId(29), ReferenceId(31), ReferenceId(33), ReferenceId(35), ReferenceId(37), ReferenceId(39), ReferenceId(40), ReferenceId(41), ReferenceId(43), ReferenceId(44), ReferenceId(46), ReferenceId(48), ReferenceId(50), ReferenceId(52)]
 rebuilt        : SymbolId(1): []
 Reference symbol mismatch for "dec":
 after transform: SymbolId(0) "dec"

tasks/transform_conformance/snapshots/oxc.snap.md

@@ -1,6 +1,6 @@
 commit: 41d96516
 
-Passed: 188/316
+Passed: 188/317
 
 # All Passed:
 * babel-plugin-transform-class-static-block
@@ -544,7 +544,7 @@ x Output mismatch
 x Output mismatch
 
 
-# legacy-decorators (6/85)
+# legacy-decorators (6/86)
 * oxc/class-without-name-with-decorated_class/input.ts
 Bindings mismatch:
 after transform: ScopeId(0): ["dec"]
@@ -698,6 +698,26 @@ Symbol reference IDs mismatch for "ComputedEnum":
 after transform: SymbolId(25): [ReferenceId(19), ReferenceId(72)]
 rebuilt        : SymbolId(15): [ReferenceId(52)]
 
+* oxc/metadata/getter-setter-method/input.ts
+Bindings mismatch:
+after transform: ScopeId(0): ["C", "dec"]
+rebuilt        : ScopeId(0): ["C"]
+Scope children mismatch:
+after transform: ScopeId(0): [ScopeId(1), ScopeId(2)]
+rebuilt        : ScopeId(0): [ScopeId(1)]
+Reference symbol mismatch for "dec":
+after transform: SymbolId(0) "dec"
+rebuilt        : <None>
+Reference symbol mismatch for "dec":
+after transform: SymbolId(0) "dec"
+rebuilt        : <None>
+Reference symbol mismatch for "dec":
+after transform: SymbolId(0) "dec"
+rebuilt        : <None>
+Unresolved references mismatch:
+after transform: ["Function", "PropertyDescriptor", "String", "babelHelpers"]
+rebuilt        : ["Function", "String", "babelHelpers", "dec"]
+
 * oxc/metadata/imports/input.ts
 Bindings mismatch:
 after transform: ScopeId(0): ["Bar", "Cls", "Foo", "Zoo", "_ref", "dec"]

tasks/transform_conformance/tests/legacy-decorators/test/fixtures/oxc/metadata/getter-setter-method/input.ts

@@ -0,0 +1,17 @@
+declare function dec(target: any, propertyKey: string, descriptor: PropertyDescriptor): void;
+
+class C {
+    @dec
+    get address(): string {
+        return "test";
+    }
+
+    @dec
+    set address(value: string) {
+    }
+
+    @dec
+    regularMethod(): string {
+        return "test";
+    }
+}

tasks/transform_conformance/tests/legacy-decorators/test/fixtures/oxc/metadata/getter-setter-method/output.js

@@ -0,0 +1,26 @@
+class C {
+    get address() {
+        return "test";
+    }
+    set address(value) {
+    }
+    regularMethod() {
+        return "test";
+    }
+}
+babelHelpers.decorate([
+    dec,
+    babelHelpers.decorateMetadata("design:type", Function),
+    babelHelpers.decorateMetadata("design:paramtypes", [])
+], C.prototype, "address", null);
+babelHelpers.decorate([
+    dec,
+    babelHelpers.decorateMetadata("design:type", Function),
+    babelHelpers.decorateMetadata("design:paramtypes", [String])
+], C.prototype, "address", null);
+babelHelpers.decorate([
+    dec,
+    babelHelpers.decorateMetadata("design:type", Function),
+    babelHelpers.decorateMetadata("design:paramtypes", []),
+    babelHelpers.decorateMetadata("design:returntype", String)
+], C.prototype, "regularMethod", null);