fix(@angular/build): deduplicate and merge coverage excludes with vitest

Previously, providing a --coverage-exclude CLI option to the builder would completely clobber any custom coverage.exclude items defined natively within vitest.config.ts.

This correctly merges both sources using an internal Set to prevent duplicate exclusions and preserves configurations so developers can combine global ignores alongside CLI-specific boundaries.

Author: clydin

packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts

@@ -437,12 +437,15 @@ async function generateCoverageOption(
     // Special handling for `exclude`/`reporters` due to an undefined value causing upstream failures
     ...(optionsCoverage.exclude
       ? {
-          exclude: [
-            // Augment the default exclude https://vitest.dev/config/#coverage-exclude
-            // with the user defined exclusions
-            ...optionsCoverage.exclude,
-            ...defaultExcludes,
-          ],
+          exclude: Array.from(
+            new Set([
+              // Augment the default exclude https://vitest.dev/config/#coverage-exclude
+              // with the user defined exclusions
+              ...(configCoverage?.exclude || []),
+              ...optionsCoverage.exclude,
+              ...defaultExcludes,
+            ]),
+          ),
         }
       : {}),
     ...(optionsCoverage.reporters

packages/angular/build/src/builders/unit-test/tests/behavior/runner-config-vitest_spec.ts

@@ -164,6 +164,59 @@ describeBuilder(execute, UNIT_TEST_BUILDER_INFO, (harness) => {
       expect(results.numPassedTests).toBe(1);
     });
 
+    it('should correctly merge coverage.exclude arrays from builder and runner options', async () => {
+      harness.useTarget('test', {
+        ...BASE_OPTIONS,
+        coverage: true,
+        runnerConfig: 'vitest.config.ts',
+        coverageExclude: ['src/app/cli-excluded.ts'],
+      });
+
+      harness.writeFile(
+        'vitest.config.ts',
+        `
+        import { defineConfig } from 'vitest/config';
+        export default defineConfig({
+          test: {
+            coverage: {
+              exclude: ['src/app/config-excluded.ts'],
+            },
+          },
+        });
+        `,
+      );
+
+      // Create two files that would normally be covered
+      harness.writeFile('src/app/cli-excluded.ts', 'export const cliExcluded = true;');
+      harness.writeFile('src/app/config-excluded.ts', 'export const configExcluded = true;');
+
+      // Update the test file to import them so they're picked up by coverage
+      harness.writeFile(
+        'src/app/app.component.spec.ts',
+        `
+        import { test, expect } from 'vitest';
+        import './cli-excluded';
+        import './config-excluded';
+        test('should pass', () => {
+          expect(true).toBe(true);
+        });
+        `,
+      );
+
+      const { result } = await harness.executeOnce();
+      expect(result?.success).toBeTrue();
+      harness.expectFile('coverage/test/coverage-final.json').toExist();
+
+      const coverageMap = JSON.parse(harness.readFile('coverage/test/coverage-final.json'));
+      const coveredFiles = Object.keys(coverageMap);
+
+      const hasCliExcluded = coveredFiles.some((f) => f.includes('cli-excluded.ts'));
+      const hasConfigExcluded = coveredFiles.some((f) => f.includes('config-excluded.ts'));
+
+      expect(hasCliExcluded).withContext('CLI target should be excluded').toBeFalse();
+      expect(hasConfigExcluded).withContext('Config file target should be excluded').toBeFalse();
+    });
+
     it('should allow overriding globals to false via runnerConfig file', async () => {
       harness.useTarget('test', {
         ...BASE_OPTIONS,