feat(@angular-devkit/build-angular): move browser-sync as optional dependency

`browser-sync` is now an optional dependency of `@angular-devkit/build-angular`. This package is only needed when using the legacy `@angular-devkit/build-angular:ssr-dev-server` builder.

Closes angular#26349

Author: alan-agius4

goldens/public-api/angular_devkit/build_angular/index.md

@@ -240,7 +240,7 @@ export function executeServerBuilder(options: ServerBuilderOptions, context: Bui
 }): Observable<ServerBuilderOutput>;
 
 // @public (undocumented)
-export function executeSSRDevServerBuilder(options: SSRDevServerBuilderOptions, context: BuilderContext): Observable<SSRDevServerBuilderOutput>;
+export function executeSSRDevServerBuilder(options: SSRDevServerBuilderOptions, context: BuilderContext): Observable<SSRDevServerBuilderOutput> | SSRDevServerBuilderOutput;
 
 // @public
 export type ExecutionTransformer<T> = (input: T) => T | Promise<T>;

packages/angular_devkit/build_angular/package.json

@@ -27,7 +27,6 @@
     "babel-loader": "9.1.3",
     "babel-plugin-istanbul": "6.1.1",
     "browserslist": "^4.21.5",
-    "browser-sync": "2.29.3",
     "chokidar": "3.5.3",
     "copy-webpack-plugin": "11.0.0",
     "critters": "0.0.20",
@@ -80,6 +79,7 @@
     "@angular/localize": "^17.0.0 || ^17.1.0-next.0",
     "@angular/platform-server": "^17.0.0 || ^17.1.0-next.0",
     "@angular/service-worker": "^17.0.0 || ^17.1.0-next.0",
+    "browser-sync": "^2.29.3",
     "jest": "^29.5.0",
     "jest-environment-jsdom": "^29.5.0",
     "karma": "^6.3.0",
@@ -98,6 +98,9 @@
     "@angular/service-worker": {
       "optional": true
     },
+    "browser-sync": {
+      "optional": true
+    },
     "jest": {
       "optional": true
     },

packages/angular_devkit/build_angular/src/builders/ssr-dev-server/index.ts

@@ -57,7 +57,7 @@ export type SSRDevServerBuilderOutput = BuilderOutput & {
 export function execute(
   options: SSRDevServerBuilderOptions,
   context: BuilderContext,
-): Observable<SSRDevServerBuilderOutput> {
+): Observable<SSRDevServerBuilderOutput> | SSRDevServerBuilderOutput {
   const browserTarget = targetFromTargetString(options.browserTarget);
   const serverTarget = targetFromTargetString(options.serverTarget);
   const getBaseUrl = (bs: BrowserSyncInstance) =>
@@ -76,7 +76,18 @@ export function execute(
     verbose: options.verbose,
   } as json.JsonObject);
 
-  const bsInstance = require('browser-sync').create();
+  let browserSync: typeof import('browser-sync');
+  try {
+    browserSync = require('browser-sync');
+  } catch {
+    return {
+      success: false,
+      error:
+        '"browser-sync" is not installed, most likely you need to run `npm install browser-sync --save-dev` in your project.',
+    };
+  }
+
+  const bsInstance = browserSync.create();
 
   context.logger.error(tags.stripIndents`
   ****************************************************************************************

packages/schematics/angular/migrations/migration-collection.json

@@ -15,6 +15,11 @@
       "factory": "./update-17/update-workspace-config",
       "description": "Replace deprecated options in 'angular.json'."
     },
+    "add-browser-sync-dependency": {
+      "version": "17.1.0",
+      "factory": "./update-17/add-browser-sync-dependency",
+      "description": "Add 'browser-sync' as dev dependency when '@angular-devkit/build-angular:ssr-dev-server' is used, as it is no longer a direct dependency of '@angular-devkit/build-angular'."
+    },
     "use-application-builder": {
       "version": "18.0.0",
       "factory": "./update-17/use-application-builder",

packages/schematics/angular/migrations/update-17/add-browser-sync-dependency.ts

@@ -0,0 +1,39 @@
+/**
+ * @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
+ */
+
+import { Rule } from '@angular-devkit/schematics';
+import { DependencyType, addDependency } from '../../utility';
+import { getPackageJsonDependency } from '../../utility/dependencies';
+import { getWorkspace } from '../../utility/workspace';
+import { Builders, ProjectType } from '../../utility/workspace-models';
+
+const BROWSER_SYNC_VERSION = '^2.29.3';
+const BROWSER_SYNC_NAME = 'browser-sync';
+
+export default function (): Rule {
+  return async (tree) => {
+    if (getPackageJsonDependency(tree, BROWSER_SYNC_NAME)?.version === BROWSER_SYNC_VERSION) {
+      return;
+    }
+
+    const workspace = await getWorkspace(tree);
+    for (const project of workspace.projects.values()) {
+      if (project.extensions.projectType !== ProjectType.Application) {
+        continue;
+      }
+
+      for (const target of project.targets.values()) {
+        if (target.builder === Builders.SsrDevServer) {
+          return addDependency(BROWSER_SYNC_NAME, BROWSER_SYNC_VERSION, {
+            type: DependencyType.Dev,
+          });
+        }
+      }
+    }
+  };
+}

packages/schematics/angular/migrations/update-17/add-browser-sync-dependency_spec.ts

@@ -0,0 +1,93 @@
+/**
+ * @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
+ */
+
+import { EmptyTree } from '@angular-devkit/schematics';
+import { SchematicTestRunner, UnitTestTree } from '@angular-devkit/schematics/testing';
+import { Builders, ProjectType, WorkspaceSchema } from '../../utility/workspace-models';
+
+describe(`Migration to add 'browser-sync' as a dev dependency`, () => {
+  const schematicName = 'add-browser-sync-dependency';
+  const schematicRunner = new SchematicTestRunner(
+    'migrations',
+    require.resolve('../migration-collection.json'),
+  );
+
+  let tree: UnitTestTree;
+  beforeEach(() => {
+    tree = new UnitTestTree(new EmptyTree());
+    tree.create(
+      '/package.json',
+      JSON.stringify(
+        {
+          devDependencies: {},
+        },
+        undefined,
+        2,
+      ),
+    );
+  });
+
+  it(`should add 'browser-sync' as devDependencies when '@angular-devkit/build-angular:ssr-dev-server' is used`, async () => {
+    tree.create(
+      '/angular.json',
+      JSON.stringify(
+        {
+          version: 1,
+          projects: {
+            app: {
+              root: '',
+              projectType: ProjectType.Application,
+              prefix: 'app',
+              architect: {
+                'serve-ssr': {
+                  builder: Builders.SsrDevServer,
+                  options: {},
+                },
+              },
+            },
+          },
+        },
+        undefined,
+        2,
+      ),
+    );
+
+    const newTree = await schematicRunner.runSchematic(schematicName, {}, tree);
+    const { devDependencies } = JSON.parse(newTree.readContent('/package.json'));
+    expect(devDependencies['browser-sync']).toBe('^2.29.3');
+  });
+
+  it(`should not add 'browser-sync' as devDependencies when '@angular-devkit/build-angular:ssr-dev-server' is not used`, async () => {
+    tree.create(
+      '/angular.json',
+      JSON.stringify(
+        {
+          version: 1,
+          projects: {
+            app: {
+              root: '',
+              projectType: ProjectType.Application,
+              prefix: 'app',
+              architect: {
+                'serve-ssr': {
+                  builder: Builders.Browser,
+                  options: {},
+                },
+              },
+            },
+          },
+        },
+        undefined,
+        2,
+      ),
+    );
+    const newTree = await schematicRunner.runSchematic(schematicName, {}, tree);
+    const { devDependencies } = JSON.parse(newTree.readContent('/package.json'));
+    expect(devDependencies['browser-sync']).toBeUndefined();
+  });
+});