fix(@angular-devkit/build-angular): export @angular/platform-server symbols in server bundle

With this commit we add an internal file to export all of the symbols from `@angular/platform-server` when building a server bundle. This is needed.  This is needed so that DI tokens can be referenced and set at runtime outside of the bundle.

Author: alan-agius4

packages/angular_devkit/build_angular/src/builders/server/index.ts

@@ -91,6 +91,8 @@ export function execute(
 
   return from(initialize(options, context, transforms.webpackConfiguration)).pipe(
     concatMap(({ config, i18n, target }) => {
+      addPlatformServerExportsAsEntry(config, root);
+
       return runWebpack(config, context, {
         webpackFactory: require('webpack') as typeof webpack,
         logging: (stats, config) => {
@@ -187,3 +189,27 @@ async function initialize(
 
   return { config: transformedConfig || config, i18n, target };
 }
+/**
+ * Add `@angular/platform-server` exports as an entry-point.
+ * This is needed so that DI tokens can be referenced and set at runtime outside of the bundle.
+ */
+function addPlatformServerExportsAsEntry(config: webpack.Configuration, root: string): void {
+  try {
+    // Only add `@angular/platform-server` exports when it is installed.
+    // In some cases this builder is used when `@angular/platform-server` is not installed.
+    // Example: when using `@nguniversal/common/clover` which does not need `@angular/platform-server`.
+    require.resolve('@angular/platform-server', { paths: [root] });
+  } catch {
+    return;
+  }
+
+  const platformServerExportsFile = path.join(__dirname, 'platform-server-exports.js');
+
+  if (typeof config.entry === 'object' && !Array.isArray(config.entry) && config.entry['main']) {
+    if (Array.isArray(config.entry['main'])) {
+      config.entry['main'].push(platformServerExportsFile);
+    } else {
+      config.entry['main'] = [platformServerExportsFile, config.entry['main'] as string];
+    }
+  }
+}

packages/angular_devkit/build_angular/src/builders/server/platform-server-exports.js

@@ -0,0 +1,9 @@
+/**
+ * @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.io/license
+ */
+
+export * from '@angular/platform-server';