fix(@angular/build): resolve Angular locale data namespace in esbuild

A transient error can occur during `ng serve` when Vite's dependency pre-bundling is triggered for Angular locale data, showing an error like `[vite] (ssr) Error when evaluating SSR module...: There is a new version of the pre-bundle...`.

Previously, the `angular:locale/data:` namespace was left unresolved by the build process for the dev server. This caused Vite to treat the namespace as a new dependency, triggering a pre-bundling step that led to the error.

With this change, esbuild now resolves the `angular:locale/data:` namespace and replaces it with the direct module import path. While the module is still treated as an external dependency, providing the explicit path prevents Vite from unnecessarily triggering a new pre-bundling phase. This resolves the transient error.

Closes #31498

Author: alan-agius4

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

@@ -12,7 +12,6 @@ import type { Connect, InlineConfig, SSROptions, ServerOptions } from 'vite';
 import type { ComponentStyleRecord } from '../../../tools/vite/middlewares';
 import {
   ServerSsrMode,
-  createAngularLocaleDataPlugin,
   createAngularMemoryPlugin,
   createAngularSetupMiddlewaresPlugin,
   createAngularSsrTransformPlugin,
@@ -221,7 +220,6 @@ export async function setupServer(
       define,
     ),
     plugins: [
-      createAngularLocaleDataPlugin(),
       createAngularSetupMiddlewaresPlugin({
         outputFiles,
         assets,

packages/angular/build/src/tools/esbuild/i18n-locale-plugin.ts

@@ -6,7 +6,8 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import type { Plugin } from 'esbuild';
+import type { Plugin, ResolveResult } from 'esbuild';
+import { createRequire } from 'node:module';
 
 /**
  * The internal namespace used by generated locale import statements and Angular locale data plugin.
@@ -27,17 +28,6 @@ export function createAngularLocaleDataPlugin(): Plugin {
   return {
     name: 'angular-locale-data',
     setup(build): void {
-      // If packages are configured to be external then leave the original angular locale import path.
-      // This happens when using the development server with caching enabled to allow Vite prebundling to work.
-      // There currently is no option on the esbuild resolve function to resolve while disabling the option. To
-      // workaround the inability to resolve the full locale location here, the Vite dev server prebundling also
-      // contains a plugin to allow the locales to be correctly resolved when prebundling.
-      // NOTE: If esbuild eventually allows controlling the external package options in a build.resolve call, this
-      //       workaround can be removed.
-      if (build.initialOptions.packages === 'external') {
-        return;
-      }
-
       build.onResolve({ filter: /^angular:locale\/data:/ }, async ({ path }) => {
         // Extract the locale from the path
         const rawLocaleTag = path.split(':', 3)[2];
@@ -60,6 +50,7 @@ export function createAngularLocaleDataPlugin(): Plugin {
         }
 
         let exact = true;
+        let localeRequire: NodeJS.Require | undefined;
         while (partialLocaleTag) {
           // Angular embeds the `en`/`en-US` locale into the framework and it does not need to be included again here.
           // The onLoad hook below for the locale data namespace has an `empty` loader that will prevent inclusion.
@@ -73,11 +64,39 @@ export function createAngularLocaleDataPlugin(): Plugin {
 
           // Attempt to resolve the locale tag data within the Angular base module location
           const potentialPath = `${LOCALE_DATA_BASE_MODULE}/${partialLocaleTag}`;
-          const result = await build.resolve(potentialPath, {
-            kind: 'import-statement',
-            resolveDir: build.initialOptions.absWorkingDir,
-          });
-          if (result.path) {
+
+          // If packages are configured to be external then leave the original angular locale import path.
+          // This happens when using the development server with caching enabled to allow Vite prebundling to work.
+          // There currently is no option on the esbuild resolve function to resolve while disabling the option.
+          // NOTE: If esbuild eventually allows controlling the external package options in a build.resolve call, this
+          // workaround can be removed.
+          let result: ResolveResult | undefined;
+          const { packages, absWorkingDir } = build.initialOptions;
+          if (packages === 'external' && absWorkingDir) {
+            localeRequire ??= createRequire(absWorkingDir + '/');
+
+            try {
+              localeRequire.resolve(potentialPath);
+
+              result = {
+                errors: [],
+                warnings: [],
+                external: true,
+                sideEffects: true,
+                namespace: '',
+                suffix: '',
+                pluginData: undefined,
+                path: potentialPath,
+              };
+            } catch {}
+          } else {
+            result = await build.resolve(potentialPath, {
+              kind: 'import-statement',
+              resolveDir: absWorkingDir,
+            });
+          }
+
+          if (result?.path) {
             if (exact) {
               return result;
             } else {

packages/angular/build/src/tools/vite/plugins/i18n-locale-plugin.ts

@@ -7,7 +7,6 @@
  */
 
 export { createAngularMemoryPlugin } from './angular-memory-plugin';
-export { createAngularLocaleDataPlugin } from './i18n-locale-plugin';
 export { createRemoveIdPrefixPlugin } from './id-prefix-plugin';
 export { createAngularSetupMiddlewaresPlugin, ServerSsrMode } from './setup-middlewares-plugin';
 export { createAngularSsrTransformPlugin } from './ssr-transform-plugin';