angular · arturovt · Jun 18, 2026
diff --git a/packages/angular/build/src/tools/angular/compilation/angular-compilation.ts b/packages/angular/build/src/tools/angular/compilation/angular-compilation.ts
@@ -9,8 +9,14 @@
 import type * as ng from '@angular/compiler-cli';
 import type { PartialMessage } from 'esbuild';
 import type ts from 'typescript';
+import { isMainThread } from 'node:worker_threads';
 import { convertTypeScriptDiagnostic } from '../../esbuild/angular/diagnostics';
-import { profileAsync, profileSync } from '../../esbuild/profiling';
+import {
+  logCumulativeDurations,
+  profileAsync,
+  profileSync,
+  resetCumulativeDurations,
+} from '../../esbuild/profiling';
 import type { AngularHostOptions } from '../angular-host';
 
 export interface EmitFileResult {
@@ -94,20 +100,39 @@ export abstract class AngularCompilation {
     // This allows for avoiding the load of typescript in the main thread when using the parallel compilation.
     const typescript = await AngularCompilation.loadTypescript();
 
-    await profileAsync('NG_DIAGNOSTICS_TOTAL', async () => {
-      for (const diagnostic of await this.collectDiagnostics(modes)) {
-        const message = convertTypeScriptDiagnostic(typescript, diagnostic);
-        if (diagnostic.category === typescript.DiagnosticCategory.Error) {
-          (result.errors ??= []).push(message);
-        } else {
-          (result.warnings ??= []).push(message);
+    // When running inside a worker (ParallelCompilation), the cumulative duration Map lives in
+    // this module's memory — the main thread never sees it. So we own the full reset→log
+    // lifecycle here rather than relying on the main thread to do it.
+    // On the main thread we skip this to avoid clearing/printing timings accumulated elsewhere.
+    const flushTimings = this.shouldFlushPerformanceTimings();
+    if (flushTimings) {
+      resetCumulativeDurations();
+    }
+
+    try {
+      await profileAsync('NG_DIAGNOSTICS_TOTAL', async () => {
+        for (const diagnostic of await this.collectDiagnostics(modes)) {
+          const message = convertTypeScriptDiagnostic(typescript, diagnostic);
+          if (diagnostic.category === typescript.DiagnosticCategory.Error) {
+            (result.errors ??= []).push(message);
+          } else {
+            (result.warnings ??= []).push(message);
+          }
         }
+      });
+    } finally {
+      if (flushTimings) {
+        logCumulativeDurations();
       }
-    });
+    }
 
     return result;
   }
 
+  protected shouldFlushPerformanceTimings(): boolean {
+    return !isMainThread;
+  }
+
   update?(files: Set<string>): Promise<void>;
 
   close?(): Promise<void>;

diff --git a/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts b/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
@@ -0,0 +1,148 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+import type * as ng from '@angular/compiler-cli';
+import type { PartialMessage } from 'esbuild';
+import type ts from 'typescript';
+import * as diagnosticsModule from '../../esbuild/angular/diagnostics';
+import * as profilingModule from '../../esbuild/profiling';
+import type { AngularHostOptions } from '../angular-host';
+import { AngularCompilation, DiagnosticModes, EmitFileResult } from './angular-compilation';
+
+/**
+ * Minimal stub for the TypeScript module: only DiagnosticCategory is accessed in diagnoseFiles.
+ */
+const MOCK_TYPESCRIPT = {
+  DiagnosticCategory: { Error: 1, Warning: 0, Message: 2, Suggestion: 3 },
+} as unknown as typeof ts;
+
+/** Concrete subclass used to control collectDiagnostics behaviour in tests. */
+class ConcreteCompilation extends AngularCompilation {
+  private diagnostics_: ts.Diagnostic[] = [];
+  private throwError_: Error | undefined;
+
+  setDiagnostics(diagnostics: ts.Diagnostic[]): void {
+    this.diagnostics_ = diagnostics;
+  }
+
+  setThrowError(error: Error): void {
+    this.throwError_ = error;
+  }
+
+  override async initialize(
+    _tsconfig: string,
+    _hostOptions: AngularHostOptions,
+    _compilerOptionsTransformer?: (compilerOptions: ng.CompilerOptions) => ng.CompilerOptions,
+  ): Promise<{
+    affectedFiles: ReadonlySet<ts.SourceFile>;
+    compilerOptions: ng.CompilerOptions;
+    referencedFiles: readonly string[];
+  }> {
+    return {
+      affectedFiles: new Set(),
+      compilerOptions: {} as ng.CompilerOptions,
+      referencedFiles: [],
+    };
+  }
+
+  override emitAffectedFiles(): Iterable<EmitFileResult> {
+    return [];
+  }
+
+  protected override *collectDiagnostics(_modes: DiagnosticModes): Iterable<ts.Diagnostic> {
+    if (this.throwError_) {
+      throw this.throwError_;
+    }
+    yield* this.diagnostics_;
+  }
+
+  protected override shouldFlushPerformanceTimings(): boolean {
+    return true;
+  }
+}
+
+describe('AngularCompilation.diagnoseFiles', () => {
+  let compilation: ConcreteCompilation;
+  let resetSpy: jasmine.Spy;
+  let logSpy: jasmine.Spy;
+  let profileAsyncSpy: jasmine.Spy;
+
+  beforeEach(() => {
+    compilation = new ConcreteCompilation();
+
+    resetSpy = spyOn(profilingModule, 'resetCumulativeDurations');
+    logSpy = spyOn(profilingModule, 'logCumulativeDurations');
+    // Default: transparent passthrough so the real loop still runs.
+    profileAsyncSpy = spyOn(profilingModule, 'profileAsync').and.callFake(
+      <T>(_name: string, action: () => Promise<T>): Promise<T> => action(),
+    );
+    spyOn(AngularCompilation, 'loadTypescript').and.resolveTo(MOCK_TYPESCRIPT);
+  });
+
+  it('calls resetCumulativeDurations once before profileAsync', async () => {
+    const callOrder: string[] = [];
+    resetSpy.and.callFake(() => {
+      callOrder.push('reset');
+    });
+    profileAsyncSpy.and.callFake(async (_name: string, action: () => Promise<unknown>) => {
+      callOrder.push('profileAsync');
+      return action();
+    });
+
+    await compilation.diagnoseFiles();
+
+    expect(resetSpy).toHaveBeenCalledTimes(1);
+    expect(callOrder).toEqual(['reset', 'profileAsync']);
+  });
+
+  it('calls logCumulativeDurations once after profileAsync completes, even with no diagnostics', async () => {
+    const callOrder: string[] = [];
+    profileAsyncSpy.and.callFake(async (_name: string, action: () => Promise<unknown>) => {
+      const result = await action();
+      callOrder.push('profileAsync-done');
+      return result;
+    });
+    logSpy.and.callFake(() => {
+      callOrder.push('log');
+    });
+
+    await compilation.diagnoseFiles();
+
+    expect(logSpy).toHaveBeenCalledTimes(1);
+    expect(callOrder).toEqual(['profileAsync-done', 'log']);
+  });
+
+  it('returns correct errors and warnings, unaffected by profiling calls', async () => {
+    const errorDiagnostic = { category: 1 /* Error */ } as ts.Diagnostic;
+    const warningDiagnostic = { category: 0 /* Warning */ } as ts.Diagnostic;
+    compilation.setDiagnostics([errorDiagnostic, warningDiagnostic]);
+
+    spyOn(diagnosticsModule, 'convertTypeScriptDiagnostic').and.callFake(
+      (_ts: typeof ts, diagnostic: ts.Diagnostic): PartialMessage => ({
+        text: diagnostic.category === 1 ? 'error message' : 'warning message',
+      }),
+    );
+
+    const result = await compilation.diagnoseFiles();
+
+    expect(result.errors).toEqual([{ text: 'error message' }]);
+    expect(result.warnings).toEqual([{ text: 'warning message' }]);
+    // Profiling hooks ran but did not affect the diagnostic output.
+    expect(resetSpy).toHaveBeenCalledTimes(1);
+    expect(logSpy).toHaveBeenCalledTimes(1);
+  });
+
+  it('calls logCumulativeDurations even when collectDiagnostics throws, and re-throws the error', async () => {
+    // logCumulativeDurations sits in a finally block, so it always runs regardless of errors.
+    compilation.setThrowError(new Error('diagnostics failure'));
+
+    await expectAsync(compilation.diagnoseFiles()).toBeRejectedWithError('diagnostics failure');
+
+    expect(logSpy).toHaveBeenCalledTimes(1);
+  });
+});