fix(api-extractor): preserve export keyword for namespace re-exports (#5517)

* fix(api-extractor): preserve export keyword for namespace re-exports

When a namespace contains `export { Foo, Bar };` re-export declarations,
api-extractor was incorrectly stripping the `export` keyword, producing
`{ Foo, Bar, };` which is syntactically invalid TypeScript (TS1109).

This fix checks if an ExportKeyword is part of an ExportDeclaration that
is inside a ModuleBlock (namespace body), and if so, preserves it instead
of stripping it.

Fixes #5516

* chore: add rush change file

* chore: update test snapshots for namespace export fix

* DRY-er

Author: ItsChrisHickman

apps/api-extractor/src/generators/ApiReportGenerator.ts

@@ -302,6 +302,14 @@ export class ApiReportGenerator {
         break;
 
       case ts.SyntaxKind.ExportKeyword:
+        if (DtsEmitHelpers.isExportKeywordInNamespaceExportDeclaration(span.node)) {
+          // This is an export declaration inside a namespace - preserve the export keyword
+          break;
+        }
+        // Otherwise, delete the export keyword -- we will re-add it below
+        span.modification.skipAll();
+        break;
+
       case ts.SyntaxKind.DefaultKeyword:
       case ts.SyntaxKind.DeclareKeyword:
         // Delete any explicit "export" or "declare" keywords -- we will re-add them below

apps/api-extractor/src/generators/DtsEmitHelpers.ts

@@ -12,6 +12,7 @@ import type { Collector } from '../collector/Collector';
 import type { Span } from '../analyzer/Span';
 import type { IndentedWriter } from './IndentedWriter';
 import { SourceFileLocationFormatter } from '../analyzer/SourceFileLocationFormatter';
+import { TypeScriptHelpers } from '../analyzer/TypeScriptHelpers';
 
 /**
  * Some common code shared between DtsRollupGenerator and ApiReportGenerator.
@@ -171,4 +172,22 @@ export class DtsEmitHelpers {
       }
     }
   }
+
+  /**
+   * Checks if an export keyword is part of an ExportDeclaration inside a namespace
+   * (e.g., "export { Foo, Bar };" inside "declare namespace SDK { ... }").
+   * In that case, the export keyword must be preserved, otherwise the output is invalid TypeScript.
+   */
+  public static isExportKeywordInNamespaceExportDeclaration(node: ts.Node): boolean {
+    if (node.parent && ts.isExportDeclaration(node.parent)) {
+      const moduleBlock: ts.ModuleBlock | undefined = TypeScriptHelpers.findFirstParent(
+        node,
+        ts.SyntaxKind.ModuleBlock
+      );
+      if (moduleBlock) {
+        return true;
+      }
+    }
+    return false;
+  }
 }

apps/api-extractor/src/generators/DtsRollupGenerator.ts

@@ -270,6 +270,14 @@ export class DtsRollupGenerator {
         break;
 
       case ts.SyntaxKind.ExportKeyword:
+        if (DtsEmitHelpers.isExportKeywordInNamespaceExportDeclaration(span.node)) {
+          // This is an export declaration inside a namespace - preserve the export keyword
+          break;
+        }
+        // Otherwise, delete the export keyword -- we will re-add it below
+        span.modification.skipAll();
+        break;
+
       case ts.SyntaxKind.DefaultKeyword:
       case ts.SyntaxKind.DeclareKeyword:
         // Delete any explicit "export" or "declare" keywords -- we will re-add them below

build-tests/api-extractor-scenarios/etc/apiItemKinds/api-extractor-scenarios.api.md

@@ -51,7 +51,7 @@ export namespace n1 {
     // (undocumented)
     export class SomeClass2 extends SomeClass1 {
     }
-        {};
+    export {};
 }
 
 // @public (undocumented)

build-tests/api-extractor-scenarios/etc/apiItemKinds/rollup.d.ts

@@ -36,7 +36,7 @@ export declare namespace n1 {
         export class SomeClass3 {
         }
     }
-        {};
+    export {};
 }
 
 /** @public */

build-tests/api-extractor-scenarios/etc/includeForgottenExports/api-extractor-scenarios.api.md

@@ -86,7 +86,7 @@ export namespace SomeNamespace1 {
     }
     // (undocumented)
     export function someFunction3(): ForgottenExport3;
-        {};
+    export {};
 }
 
 // (No @packageDocumentation comment for this package)

build-tests/api-extractor-scenarios/etc/includeForgottenExports/rollup.d.ts

@@ -80,7 +80,7 @@ export declare namespace SomeNamespace1 {
     export class ForgottenExport3 {
     }
     export function someFunction3(): ForgottenExport3;
-        {};
+    export {};
 }
 
 export { }

build-tests/api-extractor-scenarios/etc/referenceTokens/api-extractor-scenarios.api.md

@@ -21,13 +21,13 @@ export namespace n1 {
         export function someFunction2(): SomeType2;
         // (undocumented)
         export type SomeType2 = number;
-            {};
+        export {};
     }
     // (undocumented)
     export function someFunction1(): SomeType1;
     // (undocumented)
     export type SomeType1 = number;
-        {};
+    export {};
 }
 
 // @public (undocumented)

build-tests/api-extractor-scenarios/etc/referenceTokens/rollup.d.ts

@@ -14,9 +14,9 @@ export declare namespace n1 {
             export type SomeType3 = number;
             export function someFunction3(): n2.n3.SomeType3;
         }
-            {};
+        export {};
     }
-        {};
+    export {};
 }
 
 /** @public */

common/changes/@microsoft/api-extractor/fix-namespace-export-keyword_2025-12-24-17-25.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "comment": "Fix missing 'export' keyword for namespace re-exports that produced invalid TypeScript output",
+      "type": "patch",
+      "packageName": "@microsoft/api-extractor"
+    }
+  ],
+  "packageName": "@microsoft/api-extractor",
+  "email": "[email protected]"
+}