fix(@angular-devkit/build-angular): ensure all configured assets can be served by dev server

The Vite-based development server restricts filesystem access by default. However, assets
configured by the build option `assets` are intended to be accessible by the application at
runtime. To ensure that these files are accessible, the allow list will now explicitly include
all configured assets found during the build.

Author: clydin

packages/angular_devkit/build_angular/src/builders/dev-server/vite-server.ts

@@ -215,6 +215,11 @@ export async function* serveWithVite(
     }
 
     if (server) {
+      // Update fs allow list to include any new assets from the build option.
+      server.config.server.fs.allow = [
+        ...new Set(...server.config.server.fs.allow, ...assetFiles.values()),
+      ];
+
       handleUpdate(normalizePath, generatedFiles, server, serverOptions, context.logger);
     } else {
       const projectName = context.target?.project;
@@ -430,10 +435,11 @@ export async function setupServer(
     ...externalMetadata.explicit,
   ];
 
+  const cacheDir = join(serverOptions.cacheOptions.path, 'vite');
   const configuration: InlineConfig = {
     configFile: false,
     envFile: false,
-    cacheDir: join(serverOptions.cacheOptions.path, 'vite'),
+    cacheDir,
     root: virtualProjectRoot,
     publicDir: false,
     esbuild: false,
@@ -456,6 +462,13 @@ export async function setupServer(
       proxy,
       // File watching is handled by the build directly. `null` disables file watching for Vite.
       watch: null,
+      fs: {
+        // Ensure cache directory, node modules, and all assets are accessible by the client.
+        // The first two are required for Vite to function in prebundling mode (the default) and to load
+        // the Vite client-side code for browser reloading. These would be available by default but when
+        // the `allow` option is explicitly configured, they must be included manually.
+        allow: [cacheDir, join(serverOptions.workspaceRoot, 'node_modules'), ...assets.values()],
+      },
       // This is needed when `externalDependencies` is used to prevent Vite load errors.
       // NOTE: If Vite adds direct support for externals, this can be removed.
       preTransformRequests: externalMetadata.explicit.length === 0,