refactor(@angular/build): avoid secondary import wrapper in Vitest unless coverage is enabled

This commit optimizes the Vitest test runner by removing the secondary import wrapper
for test entry points when code coverage is not enabled. The wrapper is only necessary
to support coverage exclusion of the test files themselves.

By capturing the resolved Vitest configuration within the `configureVitest` hook,
the plugin can now determine if coverage is enabled and conditionally apply the
wrapper. This simplifies the module graph for standard test runs.

Author: clydin

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

@@ -14,6 +14,7 @@ import path from 'node:path';
 import type {
   BrowserConfigOptions,
   InlineConfig,
+  ResolvedConfig,
   UserWorkspaceConfig,
   VitestPlugin,
 } from 'vitest/node';
@@ -185,11 +186,15 @@ async function loadResultFile(file: ResultFile): Promise<string> {
 export function createVitestPlugins(pluginOptions: PluginOptions): VitestPlugins {
   const { workspaceRoot, buildResultFiles, testFileToEntryPoint } = pluginOptions;
   const isWindows = platform() === 'win32';
+  let vitestConfig: ResolvedConfig;
 
   return [
     {
       name: 'angular:test-in-memory-provider',
       enforce: 'pre',
+      configureVitest(context) {
+        vitestConfig = context.vitest.config;
+      },
       resolveId: (id, importer) => {
         // Fast path for test entry points.
         if (testFileToEntryPoint.has(id)) {
@@ -248,7 +253,7 @@ export function createVitestPlugins(pluginOptions: PluginOptions): VitestPlugins
         // If the module cannot be resolved from the build artifacts, let other plugins handle it.
         return undefined;
       },
-      load: async (id) => {
+      async load(id) {
         assert(buildResultFiles.size > 0, 'buildResult must be available for in-memory loading.');
 
         // Attempt to load as a source test file.
@@ -257,11 +262,14 @@ export function createVitestPlugins(pluginOptions: PluginOptions): VitestPlugins
         if (entryPoint) {
           outputPath = entryPoint + '.js';
 
-          // To support coverage exclusion of the actual test file, the virtual
-          // test entry point only references the built and bundled intermediate file.
-          return {
-            code: `import "./${outputPath}";`,
-          };
+          if (vitestConfig.coverage.enabled) {
+            // To support coverage exclusion of the actual test file, the virtual
+            // test entry point only references the built and bundled intermediate file.
+            // If vitest supported an "excludeOnlyAfterRemap" option, this could be removed completely.
+            return {
+              code: `import "./${outputPath}";`,
+            };
+          }
         } else {
           // Attempt to load as a built artifact.
           const relativePath = path.relative(workspaceRoot, id);