fix(@angular/build): resolve library bundle sourcemap sources relative to output directory

Configure `cwd` and `sourcemapPathTransform` when generating FESM and declaration bundles in the library builder so that emitted sourcemap `sources` entries are computed relative to the actual output directory.

Author: alan-agius4

packages/angular/build/src/builders/library/pipeline/bundler.ts

@@ -292,24 +292,35 @@ function processRolldownOutput(output: RolldownOutput['output'], dir: string): M
  *
  * @param input Map of bundle names to virtual entry file paths.
  * @param plugins Rolldown plugins to use during bundling.
- * @param preserveSymlinks Whether to preserve symlinks during module resolution.
  * @param extension Output file extension ('mjs' or 'd.ts').
- * @param sourcemap Whether to emit sourcemaps.
- * @param findEntryPoint Lookup function to resolve chunk entry point ownership.
+ * @param options The normalized library options.
  * @returns A promise resolving to the multi-bundle output.
  */
 async function executeMultiBundle(
   input: Record<string, string>,
   plugins: RolldownPluginOption[],
-  preserveSymlinks: boolean,
   extension: 'mjs' | 'd.ts',
-  sourcemap: boolean,
+  options: NormalizedLibraryOptions,
 ): Promise<MultiBundleOutput> {
+  const { workspaceRoot, preserveSymlinks, declarationMap, outputPath } = options;
   const isDts = extension === 'd.ts';
-  const dir = isDts ? TYPES_OUTPUT_DIR : FESM_OUTPUT_DIR;
+  const relativeOutputPath = path.posix.relative(outputPath, workspaceRoot);
+
+  let sourcemap: boolean;
+  let dir: string;
+  if (isDts) {
+    dir = TYPES_OUTPUT_DIR;
+    sourcemap = declarationMap;
+  } else {
+    dir = FESM_OUTPUT_DIR;
+    // FESM (.mjs) sourcemaps are always enabled.
+    sourcemap = true;
+  }
+
   const bundle = await rolldown({
     context: 'this',
     input,
+    cwd: workspaceRoot,
     plugins,
     treeshake: false,
     resolve: { symlinks: !preserveSymlinks },
@@ -326,6 +337,7 @@ async function executeMultiBundle(
       entryFileNames: `[name].${extension}`,
       chunkFileNames: `[name]-[hash].${extension}`,
       sourcemap,
+      sourcemapPathTransform: (sourcePath) => path.posix.join(relativeOutputPath, sourcePath),
       hoistTransitiveImports: false,
       comments: { jsdoc: isDts, legal: true, annotation: true },
     });
@@ -356,9 +368,8 @@ async function bundleAllEsm(
   return executeMultiBundle(
     resolveEntryInputMap(entryPoints, false),
     [createMemoryFileLoaderPlugin(esmFiles, ESM_EXTENSIONS, true)],
-    options.preserveSymlinks,
     'mjs',
-    true,
+    options,
   );
 }
 
@@ -389,10 +400,13 @@ async function bundleAllDts(
     dtsInput: true,
     tsconfig: false,
     sourcemap: dtsSourcemap,
+    generator: 'oxc',
   });
+
   const dtsPlugins = rawDtsPlugins.filter(
     (plugin) => plugin.name !== 'rolldown-plugin-dts:resolver',
   );
+
   assert(
     dtsPlugins.length < rawDtsPlugins.length,
     'Expected "rolldown-plugin-dts:resolver" plugin to be present in rolldown-plugin-dts.',
@@ -401,8 +415,7 @@ async function bundleAllDts(
   return executeMultiBundle(
     resolveEntryInputMap(entryPoints, true),
     [createMemoryFileLoaderPlugin(dtsFiles, DTS_EXTENSIONS, dtsSourcemap), ...dtsPlugins],
-    options.preserveSymlinks,
     'd.ts',
-    dtsSourcemap,
+    options,
   );
 }

packages/angular/build/src/builders/library/tests/behavior/build_spec.ts

@@ -6,6 +6,7 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
+import { join } from 'node:path';
 import { executeLibraryBuilder } from '../../builder';
 import { BASE_OPTIONS, LIBRARY_BUILDER_INFO, describeLibraryBuilder } from '../setup';
 
@@ -21,11 +22,16 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
       expect(result?.success).toBeTrue();
 
       harness.expectFile('dist/lib/fesm2022/lib.mjs').toExist();
-      expect(harness.hasFile('dist/lib/fesm2022/lib.mjs')).toBeTrue();
+      harness.expectFile('dist/lib/fesm2022/lib.mjs').toExist();
       const fesmContent = harness.readFile('dist/lib/fesm2022/lib.mjs');
       expect(fesmContent).toContain('LibComponent');
       expect(fesmContent).toContain('ɵcmp');
 
+      harness.expectFile('dist/lib/fesm2022/lib.mjs.map').toExist();
+      const fesmMap = JSON.parse(harness.readFile('dist/lib/fesm2022/lib.mjs.map'));
+      expect(fesmMap.sources).toContain('../../../projects/lib/src/lib/lib.component.ts');
+      harness.expectFile(join('dist/lib/fesm2022', fesmMap.sources[0])).toExist();
+
       harness.expectFile('dist/lib/types/lib.d.ts').toExist();
       const dtsContent = harness.readFile('dist/lib/types/lib.d.ts');
       expect(dtsContent).toContain('LibComponent');

packages/angular/build/src/builders/library/tests/options/declaration-map_spec.ts

@@ -8,6 +8,7 @@
 
 import { executeLibraryBuilder } from '../../builder';
 import { BASE_OPTIONS, LIBRARY_BUILDER_INFO, describeLibraryBuilder } from '../setup';
+import { join } from 'node:path';
 
 describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) => {
   describe('Option: "declarationMap"', () => {
@@ -20,9 +21,9 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
       expect(result?.success).toBeTrue();
 
       // FESM sourcemaps are always enabled
-      expect(harness.hasFile('dist/lib/fesm2022/lib.mjs.map')).toBeTrue();
+      harness.expectFile('dist/lib/fesm2022/lib.mjs.map').toExist();
       // DTS sourcemaps are disabled by default
-      expect(harness.hasFile('dist/lib/types/lib.d.ts.map')).toBeFalse();
+      harness.expectFile('dist/lib/types/lib.d.ts.map').toNotExist();
     });
 
     it('should emit declaration sourcemaps when declarationMap is true', async () => {
@@ -35,9 +36,13 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
       expect(result?.success).toBeTrue();
 
       // FESM sourcemaps are always enabled
-      expect(harness.hasFile('dist/lib/fesm2022/lib.mjs.map')).toBeTrue();
+      harness.expectFile('dist/lib/fesm2022/lib.mjs.map').toExist();
+
       // DTS sourcemaps should be generated
-      expect(harness.hasFile('dist/lib/types/lib.d.ts.map')).toBeTrue();
+      harness.expectFile('dist/lib/types/lib.d.ts.map').toExist();
+      const dtsMap = JSON.parse(harness.readFile('dist/lib/types/lib.d.ts.map'));
+      expect(dtsMap.sources).toContain('../../../projects/lib/src/lib/lib.component.ts');
+      harness.expectFile(join('dist/lib/types', dtsMap.sources[0])).toExist();
     });
   });
 });