From 78622df003352bc62d3d74dfb75ae67f8304580c Mon Sep 17 00:00:00 2001
From: Charles Lyding <19598772+clydin@users.noreply.github.com>
Date: Wed, 12 Nov 2025 20:52:30 -0500
Subject: [PATCH] fix(@angular/build): enhance Vitest dependency
 externalization and pre-bundling

This commit refactors the dependency handling for the Vitest runner to improve flexibility and correctness, especially for browser-based tests.

The previously hardcoded list of external Angular packages has been removed. Instead, a new `externalPackages: true` option is passed to the application builder, allowing for more dynamic and configurable externalization of packages. This prevents packages from `node_modules` from being bundled into the test entry points.

Note: For cases where a dependency should not be pre-bundled, the `optimizeDeps.exclude` option can be used within a custom runner configuration file.
---
 .../unit-test/runners/vitest/build-options.ts | 27 +++++--------------
 .../unit-test/runners/vitest/executor.ts      |  2 +-
 2 files changed, 8 insertions(+), 21 deletions(-)

diff --git a/packages/angular/build/src/builders/unit-test/runners/vitest/build-options.ts b/packages/angular/build/src/builders/unit-test/runners/vitest/build-options.ts
index 72152bd8c624..05aba1d9c261 100644
--- a/packages/angular/build/src/builders/unit-test/runners/vitest/build-options.ts
+++ b/packages/angular/build/src/builders/unit-test/runners/vitest/build-options.ts
@@ -14,21 +14,6 @@ import { NormalizedUnitTestBuilderOptions, injectTestingPolyfills } from '../../
 import { findTests, getTestEntrypoints } from '../../test-discovery';
 import { RunnerOptions } from '../api';
 
-/**
- * A list of Angular related packages that should be marked as external.
- * This allows Vite to pre-bundle them, improving performance.
- */
-const ANGULAR_PACKAGES_TO_EXTERNALIZE = [
-  '@angular/core',
-  '@angular/common',
-  '@angular/platform-browser',
-  '@angular/compiler',
-  '@angular/router',
-  '@angular/forms',
-  '@angular/animations',
-  'rxjs',
-];
-
 function createTestBedInitVirtualFile(
   providersFile: string | undefined,
   projectSourceRoot: string,
@@ -110,11 +95,10 @@ export async function getVitestBuildOptions(
   });
   entryPoints.set('init-testbed', 'angular:test-bed-init');
 
-  const externalDependencies = new Set(['vitest']);
-  ANGULAR_PACKAGES_TO_EXTERNALIZE.forEach((dep) => externalDependencies.add(dep));
-
+  // The 'vitest' package is always external for testing purposes
+  const externalDependencies = ['vitest'];
   if (baseBuildOptions.externalDependencies) {
-    baseBuildOptions.externalDependencies.forEach((dep) => externalDependencies.add(dep));
+    externalDependencies.push(...baseBuildOptions.externalDependencies);
   }
 
   const buildOptions: Partial<ApplicationBuilderInternalOptions> = {
@@ -135,7 +119,10 @@ export async function getVitestBuildOptions(
     outputHashing: adjustOutputHashing(baseBuildOptions.outputHashing),
     optimization: false,
     entryPoints,
-    externalDependencies: [...externalDependencies],
+    // Enable support for vitest browser prebundling. Excludes can be controlled with a runnerConfig
+    // and the `optimizeDeps.exclude` option.
+    externalPackages: true,
+    externalDependencies,
   };
 
   buildOptions.polyfills = injectTestingPolyfills(buildOptions.polyfills);
diff --git a/packages/angular/build/src/builders/unit-test/runners/vitest/executor.ts b/packages/angular/build/src/builders/unit-test/runners/vitest/executor.ts
index 21cdd05c9359..8d09550b671a 100644
--- a/packages/angular/build/src/builders/unit-test/runners/vitest/executor.ts
+++ b/packages/angular/build/src/builders/unit-test/runners/vitest/executor.ts
@@ -231,7 +231,7 @@ export class VitestExecutor implements TestExecutor {
             coverage,
             projectName,
             projectSourceRoot: this.options.projectSourceRoot,
-            optimizeDepsInclude: this.externalMetadata.explicitBrowser,
+            optimizeDepsInclude: this.externalMetadata.implicitBrowser,
             reporters,
             setupFiles: testSetupFiles,
             projectPlugins,