fix(@schematics/angular): keep existing worker tsconfig when generating another web worker

second `ng g web-worker` failed with `A merge conflicted on path "/tsconfig.worker.json"` in any workspace from `ng new` since 21.2.0, CLI formats first file with prettier and it no longer matches template
config is shared by all workers of project, so it is now written only when file is missing

Author: thekhegay

packages/schematics/angular/web-worker/index.ts

@@ -76,7 +76,7 @@ if (typeof Worker !== 'undefined') {
 }
 
 const webWorkerSchematic: RuleFactory<WebWorkerOptions> = createProjectSchematic(
-  (options, { project }) => {
+  (options, { project, tree }) => {
     const projectType = project.extensions['projectType'];
     if (projectType !== 'application') {
       throw new SchematicsException(`Web Worker requires a project type of "application".`);
@@ -95,6 +95,7 @@ const webWorkerSchematic: RuleFactory<WebWorkerOptions> = createProjectSchematic
     ]);
 
     const root = project.root || '';
+    const workerConfigPath = join(root, 'tsconfig.worker.json');
     const templateSourceWorkerConfig = apply(url('./files/worker-tsconfig'), [
       applyTemplates({
         ...options,
@@ -114,7 +115,6 @@ const webWorkerSchematic: RuleFactory<WebWorkerOptions> = createProjectSchematic
           throw new Error(`Build target is not defined for this project.`);
         }
 
-        const workerConfigPath = join(root, 'tsconfig.worker.json');
         (buildTarget.options ??= {}).webWorkerTsConfig ??= workerConfigPath;
         // The unit-test builder has no `webWorkerTsConfig` option and reads it from the build target.
         if (testTarget && testTarget.builder !== Builders.BuildUnitTest) {
@@ -125,7 +125,8 @@ const webWorkerSchematic: RuleFactory<WebWorkerOptions> = createProjectSchematic
       options.snippet ? addSnippet(options) : noop(),
       // Add the worker.
       mergeWith(templateSourceWorkerCode),
-      mergeWith(templateSourceWorkerConfig),
+      // The configuration is shared by all the workers of the project.
+      tree.exists(workerConfigPath) ? noop() : mergeWith(templateSourceWorkerConfig),
     ]);
   },
 );

packages/schematics/angular/web-worker/index_spec.ts

@@ -147,4 +147,21 @@ describe('Web Worker Schematic', () => {
     const { compilerOptions } = parseJson(tree.readContent(path).toString());
     expect(compilerOptions.outDir).toBe('./out-tsc/worker');
   });
+
+  it(`should keep the existing 'tsconfig.worker.json' when adding another worker`, async () => {
+    let tree = await schematicRunner.runSchematic('web-worker', defaultOptions, appTree);
+    // The file no longer matches the template once it was customized or formatted by the CLI.
+    const path = '/projects/bar/tsconfig.worker.json';
+    const customized = `{ "compilerOptions": { "lib": ["es2022", "webworker"] } }\n`;
+    tree.overwrite(path, customized);
+
+    tree = await schematicRunner.runSchematic(
+      'web-worker',
+      { ...defaultOptions, name: 'other' },
+      tree,
+    );
+
+    expect(tree.exists('/projects/bar/src/app/other.worker.ts')).toBeTrue();
+    expect(tree.readContent(path)).toBe(customized);
+  });
 });