Fix JSDoc comment preservation on default export in declaration emit (#2324)

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: jakebailey <[email protected]>
Co-authored-by: DanielRosenwasser <[email protected]>

Author: 3 people

internal/transformers/declarations/transform.go

@@ -1131,11 +1131,8 @@ func (tx *DeclarationTransformer) tryGetResolutionModeOverride(node *ast.Node) *
 }
 
 func (tx *DeclarationTransformer) preserveJsDoc(updated *ast.Node, original *ast.Node) {
-	// !!! TODO: JSDoc comment support
-	// if (hasJSDocNodes(updated) && hasJSDocNodes(original)) {
-	// 	updated.jsDoc = original.jsDoc;
-	// }
-	// return setCommentRange(updated, getCommentRange(original));
+	// Copy comment range from original to updated node so JSDoc comments are preserved
+	tx.EmitContext().AssignCommentRange(updated, original)
 }
 
 func (tx *DeclarationTransformer) removeAllComments(node *ast.Node) {

testdata/baselines/reference/compiler/jsdocCommentDefaultExport(module=commonjs).js

@@ -0,0 +1,86 @@
+//// [tests/cases/compiler/jsdocCommentDefaultExport.ts] ////
+
+//// [exportDefaultObject.ts]
+/** Object comment */
+export default {
+    fn() {}
+}
+
+//// [exportDefaultFunction.ts]
+/** Function comment */
+export default function() {
+    return 42;
+}
+
+//// [exportDefaultClass.ts]
+/** Class comment */
+export default class {
+    method() {}
+}
+
+//// [exportDefaultLiteral.ts]
+/** Literal comment */
+export default 42;
+
+//// [exportDefaultNull.ts]
+/** Null comment */
+export default null;
+
+
+//// [exportDefaultObject.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+/** Object comment */
+exports.default = {
+    fn() { }
+};
+//// [exportDefaultFunction.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.default = default_1;
+/** Function comment */
+function default_1() {
+    return 42;
+}
+//// [exportDefaultClass.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+/** Class comment */
+class default_1 {
+    method() { }
+}
+exports.default = default_1;
+//// [exportDefaultLiteral.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+/** Literal comment */
+exports.default = 42;
+//// [exportDefaultNull.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+/** Null comment */
+exports.default = null;
+
+
+//// [exportDefaultObject.d.ts]
+/** Object comment */
+declare const _default: {
+    fn(): void;
+};
+export default _default;
+//// [exportDefaultFunction.d.ts]
+/** Function comment */
+export default function (): number;
+//// [exportDefaultClass.d.ts]
+/** Class comment */
+export default class {
+    method(): void;
+}
+//// [exportDefaultLiteral.d.ts]
+/** Literal comment */
+declare const _default: number;
+export default _default;
+//// [exportDefaultNull.d.ts]
+/** Null comment */
+declare const _default: null;
+export default _default;

testdata/baselines/reference/compiler/jsdocCommentDefaultExport(module=commonjs).symbols

@@ -0,0 +1,33 @@
+//// [tests/cases/compiler/jsdocCommentDefaultExport.ts] ////
+
+=== exportDefaultObject.ts ===
+/** Object comment */
+export default {
+    fn() {}
+>fn : Symbol(fn, Decl(exportDefaultObject.ts, 1, 16))
+}
+
+=== exportDefaultFunction.ts ===
+
+/** Function comment */
+export default function() {
+    return 42;
+}
+
+=== exportDefaultClass.ts ===
+/** Class comment */
+export default class {
+    method() {}
+>method : Symbol(default.method, Decl(exportDefaultClass.ts, 1, 22))
+}
+
+=== exportDefaultLiteral.ts ===
+
+/** Literal comment */
+export default 42;
+
+=== exportDefaultNull.ts ===
+
+/** Null comment */
+export default null;
+

testdata/baselines/reference/compiler/jsdocCommentDefaultExport(module=commonjs).types

@@ -0,0 +1,35 @@
+//// [tests/cases/compiler/jsdocCommentDefaultExport.ts] ////
+
+=== exportDefaultObject.ts ===
+/** Object comment */
+export default {
+>{    fn() {}} : { fn(): void; }
+
+    fn() {}
+>fn : () => void
+}
+
+=== exportDefaultFunction.ts ===
+/** Function comment */
+export default function() {
+    return 42;
+>42 : 42
+}
+
+=== exportDefaultClass.ts ===
+/** Class comment */
+export default class {
+    method() {}
+>method : () => void
+}
+
+=== exportDefaultLiteral.ts ===
+
+/** Literal comment */
+export default 42;
+
+=== exportDefaultNull.ts ===
+
+/** Null comment */
+export default null;
+

testdata/baselines/reference/compiler/jsdocCommentDefaultExport(module=esnext).js

@@ -0,0 +1,74 @@
+//// [tests/cases/compiler/jsdocCommentDefaultExport.ts] ////
+
+//// [exportDefaultObject.ts]
+/** Object comment */
+export default {
+    fn() {}
+}
+
+//// [exportDefaultFunction.ts]
+/** Function comment */
+export default function() {
+    return 42;
+}
+
+//// [exportDefaultClass.ts]
+/** Class comment */
+export default class {
+    method() {}
+}
+
+//// [exportDefaultLiteral.ts]
+/** Literal comment */
+export default 42;
+
+//// [exportDefaultNull.ts]
+/** Null comment */
+export default null;
+
+
+//// [exportDefaultObject.js]
+/** Object comment */
+export default {
+    fn() { }
+};
+//// [exportDefaultFunction.js]
+/** Function comment */
+export default function () {
+    return 42;
+}
+//// [exportDefaultClass.js]
+/** Class comment */
+export default class {
+    method() { }
+}
+//// [exportDefaultLiteral.js]
+/** Literal comment */
+export default 42;
+//// [exportDefaultNull.js]
+/** Null comment */
+export default null;
+
+
+//// [exportDefaultObject.d.ts]
+/** Object comment */
+declare const _default: {
+    fn(): void;
+};
+export default _default;
+//// [exportDefaultFunction.d.ts]
+/** Function comment */
+export default function (): number;
+//// [exportDefaultClass.d.ts]
+/** Class comment */
+export default class {
+    method(): void;
+}
+//// [exportDefaultLiteral.d.ts]
+/** Literal comment */
+declare const _default: number;
+export default _default;
+//// [exportDefaultNull.d.ts]
+/** Null comment */
+declare const _default: null;
+export default _default;

testdata/baselines/reference/compiler/jsdocCommentDefaultExport(module=esnext).symbols

@@ -0,0 +1,33 @@
+//// [tests/cases/compiler/jsdocCommentDefaultExport.ts] ////
+
+=== exportDefaultObject.ts ===
+/** Object comment */
+export default {
+    fn() {}
+>fn : Symbol(fn, Decl(exportDefaultObject.ts, 1, 16))
+}
+
+=== exportDefaultFunction.ts ===
+
+/** Function comment */
+export default function() {
+    return 42;
+}
+
+=== exportDefaultClass.ts ===
+/** Class comment */
+export default class {
+    method() {}
+>method : Symbol(default.method, Decl(exportDefaultClass.ts, 1, 22))
+}
+
+=== exportDefaultLiteral.ts ===
+
+/** Literal comment */
+export default 42;
+
+=== exportDefaultNull.ts ===
+
+/** Null comment */
+export default null;
+

testdata/baselines/reference/compiler/jsdocCommentDefaultExport(module=esnext).types

@@ -0,0 +1,35 @@
+//// [tests/cases/compiler/jsdocCommentDefaultExport.ts] ////
+
+=== exportDefaultObject.ts ===
+/** Object comment */
+export default {
+>{    fn() {}} : { fn(): void; }
+
+    fn() {}
+>fn : () => void
+}
+
+=== exportDefaultFunction.ts ===
+/** Function comment */
+export default function() {
+    return 42;
+>42 : 42
+}
+
+=== exportDefaultClass.ts ===
+/** Class comment */
+export default class {
+    method() {}
+>method : () => void
+}
+
+=== exportDefaultLiteral.ts ===
+
+/** Literal comment */
+export default 42;
+
+=== exportDefaultNull.ts ===
+
+/** Null comment */
+export default null;
+

testdata/baselines/reference/submodule/compiler/jsDeclarationEmitExportAssignedFunctionWithExtraTypedefsMembers.js

@@ -32,14 +32,17 @@ module.exports = function loader(options) { };
 export type Options = {
     opt: string;
 };
+/**
+ * @param {Options} options
+ */
 declare const _default: (options: Options) => void;
 export = _default;
 
 
 //// [DtsFileErrors]
 
 
-out/index.d.ts(9,1): error TS2309: An export assignment cannot be used in a module with other exported elements.
+out/index.d.ts(12,1): error TS2309: An export assignment cannot be used in a module with other exported elements.
 
 
 ==== out/index.d.ts (1 errors) ====
@@ -50,6 +53,9 @@ out/index.d.ts(9,1): error TS2309: An export assignment cannot be used in a modu
     export type Options = {
         opt: string;
     };
+    /**
+     * @param {Options} options
+     */
     declare const _default: (options: Options) => void;
     export = _default;
     ~~~~~~~~~~~~~~~~~~

testdata/baselines/reference/submodule/compiler/jsDeclarationEmitExportAssignedFunctionWithExtraTypedefsMembers.js.diff

@@ -17,14 +17,17 @@
 +export type Options = {
      opt: string;
  };
++/**
++ * @param {Options} options
++ */
 +declare const _default: (options: Options) => void;
 +export = _default;
 +
 +
 +//// [DtsFileErrors]
 +
 +
-+out/index.d.ts(9,1): error TS2309: An export assignment cannot be used in a module with other exported elements.
++out/index.d.ts(12,1): error TS2309: An export assignment cannot be used in a module with other exported elements.
 +
 +
 +==== out/index.d.ts (1 errors) ====
@@ -35,6 +38,9 @@
 +    export type Options = {
 +        opt: string;
 +    };
++    /**
++     * @param {Options} options
++     */
 +    declare const _default: (options: Options) => void;
 +    export = _default;
 +    ~~~~~~~~~~~~~~~~~~

testdata/baselines/reference/submodule/conformance/exportDefaultExpressionComments.js

@@ -17,5 +17,8 @@ exports.default = null;
 
 
 //// [exportDefaultExpressionComments.d.ts]
+/**
+ * JSDoc Comments
+ */
 declare const _default: any;
 export default _default;