fix(@angular/build): use stable worker filenames during dev server to prevent hash changes on rebuild

During `ng serve`, web workers were always bundled with `entryNames: 'worker-[hash]'`
regardless of whether the parent build used hashing. Combined with inherited `footer`
and `splitting` options from the parent build that could change between rebuilds, this
caused the worker filename hash to change on every rebuild even when the worker content
was unchanged, breaking debugging sessions.

The fix conditionally uses `worker-[hash]` only when the parent build uses hashing
(production builds), and `worker-[name]` otherwise (dev server). It also explicitly
sets `splitting: false` and `footer: undefined` in the worker build to prevent
non-deterministic output that could affect hashing.

Closes #30494

Author: maruthang

packages/angular/build/src/builders/application/tests/behavior/rebuild-web-workers_spec.ts

@@ -17,9 +17,10 @@ import {
 
 /**
  * A regular expression used to check if a built worker is correctly referenced in application code.
+ * Matches both hashed (worker-ABCD1234.js) and non-hashed (worker-worker.js) filenames.
  */
 const REFERENCED_WORKER_REGEXP =
-  /new Worker\(new URL\("worker-[A-Z0-9]{8}\.js", import\.meta\.url\)/;
+  /new Worker\(new URL\("worker-.+\.js", import\.meta\.url\)/;
 
 describeBuilder(buildApplication, APPLICATION_BUILDER_INFO, (harness) => {
   describe('Behavior: "Rebuilds when Web Worker files change"', () => {

packages/angular/build/src/builders/application/tests/behavior/web-workers-application_spec.ts

@@ -11,9 +11,10 @@ import { APPLICATION_BUILDER_INFO, BASE_OPTIONS, describeBuilder } from '../setu
 
 /**
  * A regular expression used to check if a built worker is correctly referenced in application code.
+ * Matches both hashed (worker-ABCD1234.js) and non-hashed (worker-worker.js) filenames.
  */
 const REFERENCED_WORKER_REGEXP =
-  /new Worker\(new URL\("worker-[A-Z0-9]{8}\.js", import\.meta\.url\)/;
+  /new Worker\(new URL\("worker-.+\.js", import\.meta\.url\)/;
 
 describeBuilder(buildApplication, APPLICATION_BUILDER_INFO, (harness) => {
   describe('Behavior: "Bundles web worker files within application code"', () => {

packages/angular/build/src/tools/esbuild/angular/compiler-plugin.ts

@@ -286,8 +286,9 @@ export function createCompilerPlugin(
             );
 
             // Return bundled worker file entry name to be used in the built output
+            // Match both hashed (worker-ABCD1234.js) and non-hashed (worker-<name>.js) patterns
             const workerCodeFile = workerResult.outputFiles.find((file) =>
-              /^worker-[A-Z0-9]{8}.[cm]?js$/.test(path.basename(file.path)),
+              /^worker-.+\.[cm]?js$/.test(path.basename(file.path)),
             );
             assert(workerCodeFile, 'Web Worker bundled code file should always be present.');
             const workerCodePath = path.relative(
@@ -763,20 +764,32 @@ function bundleWebWorker(
   workerFile: string,
 ) {
   try {
+    // Use content hashing only when the parent build uses hashing in entry names.
+    // During dev server (ng serve), hashing is disabled and using it for workers
+    // causes the filename hash to change on every rebuild even when the worker
+    // content hasn't changed, breaking debugging sessions.
+    const parentEntryNames = build.initialOptions.entryNames ?? '';
+    const useHashing = parentEntryNames.includes('[hash]');
+
     return build.esbuild.buildSync({
       ...build.initialOptions,
       platform: 'browser',
       write: false,
       bundle: true,
       metafile: true,
       format: 'esm',
-      entryNames: 'worker-[hash]',
+      entryNames: useHashing ? 'worker-[hash]' : 'worker-[name]',
       entryPoints: [workerFile],
       sourcemap: pluginOptions.sourcemap,
       // Zone.js is not used in Web workers so no need to disable
       supported: undefined,
       // Plugins are not supported in sync esbuild calls
       plugins: undefined,
+      // Splitting is not needed for workers and can cause non-deterministic output
+      splitting: false,
+      // Footer may contain build-specific data (e.g., i18n hashes) that changes
+      // between rebuilds, causing unnecessary hash changes for workers
+      footer: undefined,
     });
   } catch (error) {
     if (error && typeof error === 'object' && 'errors' in error && 'warnings' in error) {