fix(@angular/build): require only the launchers the karma configuration loads

The upfront dependency validation of the unit-test builder's karma runner derives
a launcher package from each browser name. This requests packages that do not
exist, such as `karma-chromium-launcher` for `ChromiumHeadless` (provided by
`karma-chrome-launcher`) or a package named after a custom launcher defined in
a Karma configuration file, so `ng test` fails before running.

(cherry picked from commit e6c29bd)

Author: MeAkib

packages/angular/build/src/builders/unit-test/runners/karma/index.ts

@@ -22,12 +22,10 @@ const KarmaTestRunner: TestRunner = {
     checker.check('karma');
     checker.check('karma-jasmine');
 
-    // Check for browser launchers
-    if (options.browsers?.length) {
-      for (const browser of options.browsers) {
-        const launcherName = `karma-${browser.toLowerCase().split('headless')[0]}-launcher`;
-        checker.check(launcherName);
-      }
+    // A custom configuration loads its own launcher plugins and may define custom launchers.
+    // The built-in configuration only loads the Chrome launcher, which also provides Chromium.
+    if (!options.runnerConfig) {
+      checker.check('karma-chrome-launcher');
     }
 
     if (options.coverage.enabled) {

packages/angular/build/src/builders/unit-test/runners/karma/index_spec.ts

@@ -11,10 +11,14 @@ import KarmaTestRunner from './index';
 
 describe('KarmaTestRunner', () => {
   describe('validateDependencies', () => {
-    function createOptions(coverageEnabled: boolean): NormalizedUnitTestBuilderOptions {
+    function createOptions(
+      coverageEnabled: boolean,
+      options: Partial<NormalizedUnitTestBuilderOptions> = {},
+    ): NormalizedUnitTestBuilderOptions {
       return {
         projectSourceRoot: '/non-existent',
         coverage: { enabled: coverageEnabled },
+        ...options,
       } as NormalizedUnitTestBuilderOptions;
     }
 
@@ -29,5 +33,24 @@ describe('KarmaTestRunner', () => {
         /karma-coverage/,
       );
     });
+
+    it('requires karma-chrome-launcher for Chromium with the built-in configuration', () => {
+      const options = createOptions(false, { browsers: ['ChromiumHeadless'] });
+
+      expect(() => KarmaTestRunner.validateDependencies?.(options)).toThrowError(
+        /^(?!.*karma-chromium-launcher).*karma-chrome-launcher/s,
+      );
+    });
+
+    it('does not require launchers for the browsers of a custom configuration', () => {
+      const options = createOptions(false, {
+        browsers: ['ChromeNoSandbox'],
+        runnerConfig: 'karma.conf.js',
+      });
+
+      expect(() => KarmaTestRunner.validateDependencies?.(options)).toThrowError(
+        /^(?!.*-launcher)/s,
+      );
+    });
   });
 });