refactor(@angular/build): remove source-map-support from Vitest runner

This change removes the injection of `source-map-support` in Vitest browser tests and enables sourcemap rebasing for coverage runs as well. This allows Vitest's native remapper to handle stack traces and coverage correctly without needing the external polyfill in the browser. The E2E tests have been verified to pass with these changes. The unused `createSourcemapSupportPlugin` function has also been removed.

Author: clydin

packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts

@@ -232,16 +232,12 @@ export async function createVitestConfigPlugin(
         delete config.plugins;
       }
 
-      // Add browser source map support if coverage is enabled
+      // Validate browser coverage support if coverage is enabled
       if (
         (browser || testConfig?.browser?.enabled) &&
         (options.coverage.enabled || testConfig?.coverage?.enabled)
       ) {
-        // Validate that enabled browsers support the selected coverage provider
         validateBrowserCoverage(browser, testConfig?.browser, determinedProvider);
-
-        projectPlugins.unshift(createSourcemapSupportPlugin());
-        setupFiles.unshift('virtual:source-map-support');
       }
 
       const projectResolver = createRequire(projectSourceRoot + '/').resolve;
@@ -408,7 +404,7 @@ export function createVitestPlugins(pluginOptions: PluginOptions): VitestPlugins
 
           const map = sourceMapText ? JSON.parse(sourceMapText) : undefined;
           if (map) {
-            adjustSourcemapSources(map, !vitestConfig?.coverage?.enabled, workspaceRoot, id);
+            adjustSourcemapSources(map, true, workspaceRoot, id);
           }
 
           return {
@@ -475,36 +471,6 @@ function adjustSourcemapSources(
   }
 }
 
-function createSourcemapSupportPlugin(): VitestPlugins[0] {
-  return {
-    name: 'angular:source-map-support',
-    enforce: 'pre',
-    resolveId(source) {
-      if (source.includes('virtual:source-map-support')) {
-        return '\0source-map-support';
-      }
-    },
-    async load(id) {
-      if (id !== '\0source-map-support') {
-        return;
-      }
-
-      const packageResolve = createRequire(__filename).resolve;
-      const supportPath = packageResolve('source-map-support/browser-source-map-support.js');
-
-      const content = await readFile(supportPath, 'utf-8');
-
-      // The `source-map-support` library currently relies on `this` being defined in the global scope.
-      // However, when running in an ESM environment, `this` is undefined.
-      // To workaround this, we patch the library to use `globalThis` instead of `this`.
-      return (
-        content.replaceAll(/this\.(define|sourceMapSupport|base64js)/g, 'globalThis.$1') +
-        '\n;globalThis.sourceMapSupport.install();'
-      );
-    },
-  };
-}
-
 interface CustomBrowserConfigOptions {
   enabled?: boolean;
   instances?: { browser: string }[];

tests/e2e/tests/vitest/browser-coverage-sourcemaps.ts

@@ -12,20 +12,32 @@ export default async function (): Promise<void> {
 
   // Run tests with coverage in browser mode.
   // We use the default passing tests generated for the project.
-  const { stdout } = await ng('test', '--no-watch', '--browsers', 'chromiumHeadless', '--coverage');
+  const { stdout } = await ng(
+    'test',
+    '--no-watch',
+    '--browsers',
+    'chromiumHeadless',
+    '--coverage',
+    '--coverage-reporters=json-summary',
+  );
 
   // Verify that tests passed
   assert.match(stdout, /pass/, 'Expected tests to run successfully.');
 
   // Verify that coverage files are generated
-  const coverageJsonPath = 'coverage/test-project/coverage-final.json';
-  await expectFileToExist(coverageJsonPath);
-
-  const coverageContent = await readFile(coverageJsonPath);
-  assert.match(coverageContent, /app\.ts/, 'Expected coverage report to contain app.ts.');
-  assert.doesNotMatch(
-    coverageContent,
-    /\.spec\.ts/,
-    'Expected coverage report to not contain .spec.ts files.',
-  );
+  const summaryPath = 'coverage/test-project/coverage-summary.json';
+  await expectFileToExist(summaryPath);
+
+  const summary = JSON.parse(await readFile(summaryPath));
+
+  // Find the key for app.ts (it might be an absolute path)
+  const appFileKey = Object.keys(summary).find((key) => key.endsWith('app.ts'));
+  assert.ok(appFileKey, 'Expected coverage summary to contain app.ts.');
+
+  const appCoverage = summary[appFileKey];
+  assert.ok(appCoverage.lines.pct > 0, 'Expected lines percentage to be greater than 0.');
+
+  // Also verify that spec files are NOT present in the summary
+  const specFileKey = Object.keys(summary).find((key) => key.endsWith('.spec.ts'));
+  assert.ok(!specFileKey, 'Expected coverage report to not contain .spec.ts files.');
 }