fix(@angular/build): trigger browser reload on asset changes with Vite dev server

Ensures the Vite-based development server automatically reloads the browser when asset files are modified.

Closes #26141

Author: alan-agius4

packages/angular/build/src/builders/application/build-action.ts

@@ -313,10 +313,10 @@ function* emitOutputResults(
     for (const { source, destination } of assetFiles) {
       removedAssetFiles.delete(source);
 
-      if (changes.modified.has(source)) {
-        incrementalResult.modified.push(destination);
-      } else if (!previousAssetsInfo.has(source)) {
+      if (!previousAssetsInfo.has(source)) {
         incrementalResult.added.push(destination);
+      } else if (changes.modified.has(source)) {
+        incrementalResult.modified.push(destination);
       } else {
         continue;
       }

packages/angular/build/src/builders/dev-server/vite-server.ts

@@ -49,6 +49,11 @@ interface OutputFileRecord {
   type: BuildOutputFileType;
 }
 
+interface OutputAssetRecord {
+  source: string;
+  updated: boolean;
+}
+
 interface DevServerExternalResultMetadata extends Omit<ExternalResultMetadata, 'explicit'> {
   explicitBrowser: string[];
   explicitServer: string[];
@@ -168,7 +173,7 @@ export async function* serveWithVite(
   let serverUrl: URL | undefined;
   let hadError = false;
   const generatedFiles = new Map<string, OutputFileRecord>();
-  const assetFiles = new Map<string, string>();
+  const assetFiles = new Map<string, OutputAssetRecord>();
   const externalMetadata: DevServerExternalResultMetadata = {
     implicitBrowser: [],
     implicitServer: [],
@@ -229,19 +234,15 @@ export async function* serveWithVite(
         assetFiles.clear();
         componentStyles.clear();
         generatedFiles.clear();
-        for (const entry of Object.entries(result.files)) {
-          const [outputPath, file] = entry;
-          if (file.origin === 'disk') {
-            assetFiles.set('/' + normalizePath(outputPath), normalizePath(file.inputPath));
-            continue;
-          }
 
+        for (const [outputPath, file] of Object.entries(result.files)) {
           updateResultRecord(
             outputPath,
             file,
             normalizePath,
             htmlIndexPath,
             generatedFiles,
+            assetFiles,
             componentStyles,
             // The initial build will not yet have a server setup
             !server,
@@ -265,13 +266,15 @@ export async function* serveWithVite(
           generatedFiles.delete(filePath);
           assetFiles.delete(filePath);
         }
+
         for (const modified of result.modified) {
           updateResultRecord(
             modified,
             result.files[modified],
             normalizePath,
             htmlIndexPath,
             generatedFiles,
+            assetFiles,
             componentStyles,
           );
         }
@@ -282,6 +285,7 @@ export async function* serveWithVite(
             normalizePath,
             htmlIndexPath,
             generatedFiles,
+            assetFiles,
             componentStyles,
           );
         }
@@ -352,12 +356,16 @@ 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()]),
+        ...new Set([
+          ...server.config.server.fs.allow,
+          ...[...assetFiles.values()].map(({ source }) => source),
+        ]),
       ];
 
       await handleUpdate(
         normalizePath,
         generatedFiles,
+        assetFiles,
         server,
         serverOptions,
         context.logger,
@@ -471,15 +479,26 @@ export async function* serveWithVite(
 async function handleUpdate(
   normalizePath: (id: string) => string,
   generatedFiles: Map<string, OutputFileRecord>,
+  assetFiles: Map<string, OutputAssetRecord>,
   server: ViteDevServer,
   serverOptions: NormalizedDevServerOptions,
   logger: BuilderContext['logger'],
   componentStyles: Map<string, ComponentStyleRecord>,
 ): Promise<void> {
   const updatedFiles: string[] = [];
-  let destroyAngularServerAppCalled = false;
+
+  // Invadate any updated asset
+  for (const [file, record] of assetFiles) {
+    if (!record.updated) {
+      continue;
+    }
+
+    record.updated = false;
+    updatedFiles.push(file);
+  }
 
   // Invalidate any updated files
+  let destroyAngularServerAppCalled = false;
   for (const [file, record] of generatedFiles) {
     if (!record.updated) {
       continue;
@@ -584,10 +603,16 @@ function updateResultRecord(
   normalizePath: (id: string) => string,
   htmlIndexPath: string,
   generatedFiles: Map<string, OutputFileRecord>,
+  assetFiles: Map<string, OutputAssetRecord>,
   componentStyles: Map<string, ComponentStyleRecord>,
   initial = false,
 ): void {
   if (file.origin === 'disk') {
+    assetFiles.set('/' + normalizePath(outputPath), {
+      source: normalizePath(file.inputPath),
+      updated: !initial,
+    });
+
     return;
   }
 
@@ -644,7 +669,7 @@ function updateResultRecord(
 export async function setupServer(
   serverOptions: NormalizedDevServerOptions,
   outputFiles: Map<string, OutputFileRecord>,
-  assets: Map<string, string>,
+  assets: Map<string, OutputAssetRecord>,
   preserveSymlinks: boolean | undefined,
   externalMetadata: DevServerExternalResultMetadata,
   ssrMode: ServerSsrMode,
@@ -743,7 +768,11 @@ export async function setupServer(
         // 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()],
+        allow: [
+          cacheDir,
+          join(serverOptions.workspaceRoot, 'node_modules'),
+          ...[...assets.values()].map(({ source }) => source),
+        ],
       },
       // This is needed when `externalDependencies` is used to prevent Vite load errors.
       // NOTE: If Vite adds direct support for externals, this can be removed.

packages/angular/build/src/tools/vite/middlewares/assets-middleware.ts

@@ -9,7 +9,7 @@
 import { lookup as lookupMimeType } from 'mrmime';
 import { extname } from 'node:path';
 import type { Connect, ViteDevServer } from 'vite';
-import { AngularMemoryOutputFiles, pathnameWithoutBasePath } from '../utils';
+import { AngularMemoryOutputFiles, AngularOutputAssets, pathnameWithoutBasePath } from '../utils';
 
 export interface ComponentStyleRecord {
   rawContent: Uint8Array;
@@ -19,7 +19,7 @@ export interface ComponentStyleRecord {
 
 export function createAngularAssetsMiddleware(
   server: ViteDevServer,
-  assets: Map<string, string>,
+  assets: AngularOutputAssets,
   outputFiles: AngularMemoryOutputFiles,
   componentStyles: Map<string, ComponentStyleRecord>,
   encapsulateStyle: (style: Uint8Array, componentId: string) => string,
@@ -36,16 +36,16 @@ export function createAngularAssetsMiddleware(
     const pathnameHasTrailingSlash = pathname[pathname.length - 1] === '/';
 
     // Rewrite all build assets to a vite raw fs URL
-    const assetSourcePath = assets.get(pathname);
-    if (assetSourcePath !== undefined) {
+    const asset = assets.get(pathname);
+    if (asset) {
       // Workaround to disable Vite transformer middleware.
       // See: https://github.com/vitejs/vite/blob/746a1daab0395f98f0afbdee8f364cb6cf2f3b3f/packages/vite/src/node/server/middlewares/transform.ts#L201 and
       // https://github.com/vitejs/vite/blob/746a1daab0395f98f0afbdee8f364cb6cf2f3b3f/packages/vite/src/node/server/transformRequest.ts#L204-L206
       req.headers.accept = 'text/html';
 
       // The encoding needs to match what happens in the vite static middleware.
       // ref: https://github.com/vitejs/vite/blob/d4f13bd81468961c8c926438e815ab6b1c82735e/packages/vite/src/node/server/middlewares/static.ts#L163
-      req.url = `${server.config.base}@fs/${encodeURI(assetSourcePath)}`;
+      req.url = `${server.config.base}@fs/${encodeURI(asset.source)}`;
       next();
 
       return;
@@ -61,7 +61,7 @@ export function createAngularAssetsMiddleware(
         assets.get(pathname + '.html');
 
     if (htmlAssetSourcePath) {
-      req.url = `${server.config.base}@fs/${encodeURI(htmlAssetSourcePath)}`;
+      req.url = `${server.config.base}@fs/${encodeURI(htmlAssetSourcePath.source)}`;
       next();
 
       return;

packages/angular/build/src/tools/vite/plugins/setup-middlewares-plugin.ts

@@ -18,7 +18,7 @@ import {
   createAngularSsrExternalMiddleware,
   createAngularSsrInternalMiddleware,
 } from '../middlewares';
-import { AngularMemoryOutputFiles } from '../utils';
+import { AngularMemoryOutputFiles, AngularOutputAssets } from '../utils';
 
 export enum ServerSsrMode {
   /**
@@ -47,7 +47,7 @@ export enum ServerSsrMode {
 
 interface AngularSetupMiddlewaresPluginOptions {
   outputFiles: AngularMemoryOutputFiles;
-  assets: Map<string, string>;
+  assets: AngularOutputAssets;
   extensionMiddleware?: Connect.NextHandleFunction[];
   indexHtmlTransformer?: (content: string) => Promise<string>;
   componentStyles: Map<string, ComponentStyleRecord>;

packages/angular/build/src/tools/vite/utils.ts

@@ -18,6 +18,8 @@ export type AngularMemoryOutputFiles = Map<
   { contents: Uint8Array; hash: string; servable: boolean }
 >;
 
+export type AngularOutputAssets = Map<string, { source: string }>;
+
 export function pathnameWithoutBasePath(url: string, basePath: string): string {
   const parsedUrl = new URL(url, 'http://localhost');
   const pathname = decodeURIComponent(parsedUrl.pathname);