fix(@angular/build): warn when @angular/localize/init is imported directly

packages/angular/build/src/tools/esbuild/angular-localize-init-warning-plugin.ts

@@ -0,0 +1,53 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+import type { Plugin } from 'esbuild';
+
+const NG_LOCALIZE_RESOLUTION = Symbol('NG_LOCALIZE_RESOLUTION');
+
+/**
+ * This plugin addresses an issue where '@angular/localize/init' is directly imported,
+ * potentially resulting in undefined behavior. By detecting such imports, the plugin
+ * issues a warning and suggests including '@angular/localize/init' as a polyfill.
+ *
+ * @returns An esbuild plugin.
+ */
+export function createAngularLocalizeInitWarningPlugin(): Plugin {
+  return {
+    name: 'angular-localize-init-warning',
+    setup(build) {
+      build.onResolve({ filter: /^@angular\/localize\/init/ }, async (args) => {
+        if (args.pluginData?.[NG_LOCALIZE_RESOLUTION]) {
+          return null;
+        }
+
+        const { importer, kind, resolveDir, namespace, pluginData = {} } = args;
+        pluginData[NG_LOCALIZE_RESOLUTION] = true;
+
+        const result = await build.resolve(args.path, {
+          importer,
+          kind,
+          namespace,
+          pluginData,
+          resolveDir,
+        });
+
+        return {
+          ...result,
+          warnings: [
+            ...result.warnings,
+            {
+              text: `Direct import of '@angular/localize/init' detected. This may lead to undefined behavior.`,
+              notes: [{ text: `Include '@angular/localize/init' as a polyfill instead.` }],
+            },
+          ],
+        };
+      });
+    },
+  };
+}

packages/angular/build/src/tools/esbuild/application-code-bundle.ts

@@ -20,6 +20,7 @@ import {
 import { createCompilerPlugin } from './angular/compiler-plugin';
 import { ComponentStylesheetBundler } from './angular/component-stylesheets';
 import { SourceFileCache } from './angular/source-file-cache';
+import { createAngularLocalizeInitWarningPlugin } from './angular-localize-init-warning-plugin';
 import { BundlerOptionsFactory } from './bundler-context';
 import { createCompilerPluginOptions } from './compiler-plugin-options';
 import { createExternalPackagesPlugin } from './external-packages-plugin';
@@ -68,6 +69,7 @@ export function createBrowserCodeBundleOptions(
         createLoaderImportAttributePlugin(),
         createWasmPlugin({ allowAsync: zoneless, cache: loadCache }),
         createSourcemapIgnorelistPlugin(),
+        createAngularLocalizeInitWarningPlugin(),
         createCompilerPlugin(
           // JS/TS options
           pluginOptions,
@@ -288,6 +290,7 @@ export function createServerMainCodeBundleOptions(
       plugins: [
         createWasmPlugin({ allowAsync: zoneless, cache: loadResultCache }),
         createSourcemapIgnorelistPlugin(),
+        createAngularLocalizeInitWarningPlugin(),
         createCompilerPlugin(
           // JS/TS options
           { ...pluginOptions, noopTypeScriptCompilation: true },
@@ -427,6 +430,7 @@ export function createSsrEntryCodeBundleOptions(
       supported: getFeatureSupport(target, true),
       plugins: [
         createSourcemapIgnorelistPlugin(),
+        createAngularLocalizeInitWarningPlugin(),
         createCompilerPlugin(
           // JS/TS options
           { ...pluginOptions, noopTypeScriptCompilation: true },