[tools][web] Make Plugin Registrant file ephemeral. (#102185)

dev/bots/service_worker_test.dart

@@ -231,7 +231,6 @@ Future<void> runWebServiceWorkerTest({
       'main.dart.js': 1,
       'flutter_service_worker.js': 1,
       'assets/FontManifest.json': 1,
-      'assets/NOTICES': 1,
       'assets/AssetManifest.json': 1,
       'CLOSE': 1,
       // In headless mode Chrome does not load 'manifest.json' and 'favicon.ico'.
@@ -273,7 +272,6 @@ Future<void> runWebServiceWorkerTest({
         'flutter.js': 1,
       'flutter_service_worker.js': 2,
       'main.dart.js': 1,
-      'assets/NOTICES': 1,
       'assets/AssetManifest.json': 1,
       'assets/FontManifest.json': 1,
       'CLOSE': 1,
@@ -305,7 +303,6 @@ Future<void> runWebServiceWorkerTest({
       'main.dart.js': 2,
       'assets/FontManifest.json': 2,
       'flutter_service_worker.js': 1,
-      'assets/NOTICES': 1,
       'assets/AssetManifest.json': 1,
       'CLOSE': 1,
       // In headless mode Chrome does not load 'manifest.json' and 'favicon.ico'.
@@ -358,7 +355,6 @@ Future<void> runWebServiceWorkerTest({
         'flutter.js': 1,
       'flutter_service_worker.js': 2,
       'main.dart.js': 2,
-      'assets/NOTICES': 1,
       'assets/AssetManifest.json': 1,
       'assets/FontManifest.json': 2,
       'CLOSE': 1,

packages/flutter_tools/lib/src/flutter_plugins.dart

@@ -550,23 +550,32 @@ Depends on all your plugins, and provides a function to register them.
 end
 ''';
 
+const String _noopDartPluginRegistryTemplate = '''
+// Flutter web plugin registrant file.
+//
+// Generated file. Do not edit.
+//
+
+// ignore_for_file: type=lint
+
+void registerPlugins() {}
+''';
+
 const String _dartPluginRegistryTemplate = '''
+// Flutter web plugin registrant file.
 //
 // Generated file. Do not edit.
 //
 
-// ignore_for_file: directives_ordering
-// ignore_for_file: lines_longer_than_80_chars
-// ignore_for_file: depend_on_referenced_packages
+// ignore_for_file: type=lint
 
 {{#methodChannelPlugins}}
 import 'package:{{name}}/{{file}}';
 {{/methodChannelPlugins}}
-
 import 'package:flutter_web_plugins/flutter_web_plugins.dart';
 
-// ignore: public_member_api_docs
-void registerPlugins(final Registrar registrar) {
+void registerPlugins([final Registrar? pluginRegistrar]) {
+  final Registrar registrar = pluginRegistrar ?? webPluginRegistrar;
 {{#methodChannelPlugins}}
   {{class}}.registerWith(registrar);
 {{/methodChannelPlugins}}
@@ -937,22 +946,22 @@ Future<void> _writeCppPluginRegistrant(Directory destination, Map<String, Object
   );
 }
 
-Future<void> _writeWebPluginRegistrant(FlutterProject project, List<Plugin> plugins) async {
+Future<void> _writeWebPluginRegistrant(FlutterProject project, List<Plugin> plugins, Directory destination) async {
   final List<Map<String, Object?>> webPlugins = _extractPlatformMaps(plugins, WebPlugin.kConfigKey);
   final Map<String, Object> context = <String, Object>{
     'methodChannelPlugins': webPlugins,
   };
-  final File pluginFile = project.web.libDirectory.childFile('generated_plugin_registrant.dart');
-  if (webPlugins.isEmpty) {
-    ErrorHandlingFileSystem.deleteIfExists(pluginFile);
-  } else {
-    _renderTemplateToFile(
-      _dartPluginRegistryTemplate,
-      context,
-      pluginFile,
-      globals.templateRenderer,
-    );
-  }
+
+  final File pluginFile = destination.childFile('web_plugin_registrant.dart');
+
+  final String template = webPlugins.isEmpty ? _noopDartPluginRegistryTemplate : _dartPluginRegistryTemplate;
+
+  _renderTemplateToFile(
+    template,
+    context,
+    pluginFile,
+    globals.templateRenderer,
+  );
 }
 
 /// For each platform that uses them, creates symlinks within the platform
@@ -1068,8 +1077,41 @@ Future<void> refreshPluginsList(
   }
 }
 
+/// Injects plugins found in `pubspec.yaml` into the platform-specific projects
+/// only at build-time.
+///
+/// This method is similar to [injectPlugins], but used only for platforms where
+/// the plugin files are not required when the app is created (currently: Web).
+///
+/// This method will create files in the temporary flutter build directory
+/// specified by `destination`.
+///
+/// In the Web platform, `destination` can point to a real filesystem (`flutter build`)
+/// or an in-memory filesystem (`flutter run`).
+Future<void> injectBuildTimePluginFiles(
+  FlutterProject project, {
+  required Directory destination,
+  bool webPlatform = false,
+}) async {
+  final List<Plugin> plugins = await findPlugins(project);
+  // Sort the plugins by name to keep ordering stable in generated files.
+  plugins.sort((Plugin left, Plugin right) => left.name.compareTo(right.name));
+  if (webPlatform) {
+    await _writeWebPluginRegistrant(project, plugins, destination);
+  }
+}
+
 /// Injects plugins found in `pubspec.yaml` into the platform-specific projects.
 ///
+/// The injected files are required by the flutter app as soon as possible, so
+/// it can be built.
+///
+/// Files written by this method end up in platform-specific locations that are
+/// configured by each [FlutterProject] subclass (except for the Web).
+///
+/// Web tooling uses [injectBuildTimePluginFiles] instead, which places files in the
+/// current build (temp) directory, and doesn't modify the users' working copy.
+///
 /// Assumes [refreshPluginsList] has been called since last change to `pubspec.yaml`.
 Future<void> injectPlugins(
   FlutterProject project, {
@@ -1078,7 +1120,6 @@ Future<void> injectPlugins(
   bool linuxPlatform = false,
   bool macOSPlatform = false,
   bool windowsPlatform = false,
-  bool webPlatform = false,
 }) async {
   final List<Plugin> plugins = await findPlugins(project);
   // Sort the plugins by name to keep ordering stable in generated files.
@@ -1114,9 +1155,6 @@ Future<void> injectPlugins(
       }
     }
   }
-  if (webPlatform) {
-    await _writeWebPluginRegistrant(project, plugins);
-  }
 }
 
 /// Returns whether the specified Flutter [project] has any plugin dependencies.

packages/flutter_tools/lib/src/isolated/devfs_web.dart

@@ -41,7 +41,7 @@ import '../vmservice.dart';
 import '../web/bootstrap.dart';
 import '../web/chrome.dart';
 import '../web/compile.dart';
-import '../web/flutter_js.dart' as flutter_js;
+import '../web/file_generators/flutter_js.dart' as flutter_js;
 import '../web/memory_fs.dart';
 import 'sdk_web_configuration.dart';
 

packages/flutter_tools/lib/src/isolated/resident_web_runner.dart

@@ -30,8 +30,6 @@ import '../dart/language_version.dart';
 import '../devfs.dart';
 import '../device.dart';
 import '../flutter_plugins.dart';
-import '../platform_plugins.dart';
-import '../plugins.dart';
 import '../project.dart';
 import '../reporting/reporting.dart';
 import '../resident_devtools_handler.dart';
@@ -40,6 +38,7 @@ import '../run_hot.dart';
 import '../vmservice.dart';
 import '../web/chrome.dart';
 import '../web/compile.dart';
+import '../web/file_generators/main_dart.dart' as main_dart;
 import '../web/web_device.dart';
 import '../web/web_runner.dart';
 import 'devfs_web.dart';
@@ -433,15 +432,12 @@ class ResidentWebRunner extends ResidentRunner {
         ..createSync();
       result = _generatedEntrypointDirectory.childFile('web_entrypoint.dart');
 
-      final bool hasWebPlugins = (await findPlugins(flutterProject))
-        .any((Plugin p) => p.platforms.containsKey(WebPlugin.kConfigKey));
-      await injectPlugins(flutterProject, webPlatform: true);
+      // Generates the generated_plugin_registrar
+      await injectBuildTimePluginFiles(flutterProject, webPlatform: true, destination: _generatedEntrypointDirectory);
+      // The below works because `injectBuildTimePluginFiles` is configured to write
+      // the web_plugin_registrant.dart file alongside the generated main.dart
+      const String/*?*/ generatedImport = 'web_plugin_registrant.dart';
 
-      final Uri generatedUri = _fileSystem.currentDirectory
-        .childDirectory('lib')
-        .childFile('generated_plugin_registrant.dart')
-        .absolute.uri;
-      final Uri generatedImport = packageConfig.toPackageUri(generatedUri);
       Uri importedEntrypoint = packageConfig.toPackageUri(mainUri);
       // Special handling for entrypoints that are not under lib, such as test scripts.
       if (importedEntrypoint == null) {
@@ -453,44 +449,17 @@ class ResidentWebRunner extends ResidentRunner {
           path: '/${mainUri.pathSegments.last}',
         );
       }
-      final LanguageVersion languageVersion =  determineLanguageVersion(
+      final LanguageVersion languageVersion = determineLanguageVersion(
         _fileSystem.file(mainUri),
         packageConfig[flutterProject.manifest.appName],
         Cache.flutterRoot,
       );
 
-      final String entrypoint = <String>[
-        '// @dart=${languageVersion.major}.${languageVersion.minor}',
-        '// Flutter web bootstrap script for $importedEntrypoint.',
-        '',
-        "import 'dart:ui' as ui;",
-        "import 'dart:async';",
-        '',
-        "import '$importedEntrypoint' as entrypoint;",
-        if (hasWebPlugins)
-          "import 'package:flutter_web_plugins/flutter_web_plugins.dart';",
-        if (hasWebPlugins)
-          "import '$generatedImport';",
-        '',
-        'typedef _UnaryFunction = dynamic Function(List<String> args);',
-        'typedef _NullaryFunction = dynamic Function();',
-        'Future<void> main() async {',
-        '  await ui.webOnlyWarmupEngine(',
-        '    runApp: () {',
-        '      if (entrypoint.main is _UnaryFunction) {',
-        '        return (entrypoint.main as _UnaryFunction)(<String>[]);',
-        '      }',
-        '      return (entrypoint.main as _NullaryFunction)();',
-        '    },',
-        if (hasWebPlugins) ...<String>[
-        '    registerPlugins: () {',
-        '      registerPlugins(webPluginRegistrar);',
-        '    },',
-        ],
-        '  );',
-        '}',
-        '',
-      ].join('\n');
+      final String entrypoint = main_dart.generateMainDartFile(importedEntrypoint.toString(),
+        languageVersion: languageVersion,
+        pluginRegistrantEntrypoint: generatedImport,
+      );
+
       result.writeAsStringSync(entrypoint);
     }
     return result.absolute.uri;

packages/flutter_tools/lib/src/project.dart

@@ -373,7 +373,6 @@ class FlutterProject {
       linuxPlatform: linuxPlatform,
       macOSPlatform: macOSPlatform,
       windowsPlatform: windowsPlatform,
-      webPlatform: webPlatform,
     );
   }
 

packages/flutter_tools/lib/src/web/compile.dart

@@ -6,6 +6,7 @@ import '../artifacts.dart';
 import '../base/common.dart';
 import '../base/file_system.dart';
 import '../base/logger.dart';
+import '../base/project_migrator.dart';
 import '../build_info.dart';
 import '../build_system/build_system.dart';
 import '../build_system/targets/web.dart';
@@ -15,6 +16,7 @@ import '../globals.dart' as globals;
 import '../platform_plugins.dart';
 import '../plugins.dart';
 import '../project.dart';
+import 'migrations/scrub_generated_plugin_registrant.dart';
 
 Future<void> buildWeb(
   FlutterProject flutterProject,
@@ -32,7 +34,16 @@ Future<void> buildWeb(
   final Directory outputDirectory = globals.fs.directory(getWebBuildDirectory());
   outputDirectory.createSync(recursive: true);
 
-  await injectPlugins(flutterProject, webPlatform: true);
+  // The migrators to apply to a Web project.
+  final List<ProjectMigrator> migrators = <ProjectMigrator>[
+    ScrubGeneratedPluginRegistrant(flutterProject.web, globals.logger),
+  ];
+
+  final ProjectMigration migration = ProjectMigration(migrators);
+  if (!migration.run()) {
+    throwToolExit('Failed to run all web migrations.');
+  }
+
   final Status status = globals.logger.startProgress('Compiling $target for the Web...');
   final Stopwatch sw = Stopwatch()..start();
   try {

packages/flutter_tools/lib/src/web/file_generators/flutter_service_worker_js.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/// The caching strategy for the generated service worker.
+enum ServiceWorkerStrategy {
+  /// Download the app shell eagerly and all other assets lazily.
+  /// Prefer the offline cached version.
+  offlineFirst,
+  /// Do not generate a service worker,
+  none,
+}
+
+/// Generate a service worker with an app-specific cache name a map of
+/// resource files.
+///
+/// The tool embeds file hashes directly into the worker so that the byte for byte
+/// invalidation will automatically reactivate workers whenever a new
+/// version is deployed.
+String generateServiceWorker(
+  Map<String, String> resources,
+  List<String> coreBundle, {
+  required ServiceWorkerStrategy serviceWorkerStrategy,
+}) {
+  if (serviceWorkerStrategy == ServiceWorkerStrategy.none) {
+    return '';
+  }
+  return '''
+'use strict';
+const MANIFEST = 'flutter-app-manifest';
+const TEMP = 'flutter-temp-cache';
+const CACHE_NAME = 'flutter-app-cache';
+const RESOURCES = {
+  ${resources.entries.map((MapEntry<String, String> entry) => '"${entry.key}": "${entry.value}"').join(",\n")}
+};
+
+// The application shell files that are downloaded before a service worker can
+// start.
+const CORE = [
+  ${coreBundle.map((String file) => '"$file"').join(',\n')}];
+// During install, the TEMP cache is populated with the application shell files.
+self.addEventListener("install", (event) => {
+  self.skipWaiting();
+  return event.waitUntil(
+    caches.open(TEMP).then((cache) => {
+      return cache.addAll(
+        CORE.map((value) => new Request(value, {'cache': 'reload'})));
+    })
+  );
+});
+
+// During activate, the cache is populated with the temp files downloaded in
+// install. If this service worker is upgrading from one with a saved
+// MANIFEST, then use this to retain unchanged resource files.
+self.addEventListener("activate", function(event) {
+  return event.waitUntil(async function() {
+    try {
+      var contentCache = await caches.open(CACHE_NAME);
+      var tempCache = await caches.open(TEMP);
+      var manifestCache = await caches.open(MANIFEST);
+      var manifest = await manifestCache.match('manifest');
+      // When there is no prior manifest, clear the entire cache.
+      if (!manifest) {
+        await caches.delete(CACHE_NAME);
+        contentCache = await caches.open(CACHE_NAME);
+        for (var request of await tempCache.keys()) {
+          var response = await tempCache.match(request);
+          await contentCache.put(request, response);
+        }
+        await caches.delete(TEMP);
+        // Save the manifest to make future upgrades efficient.
+        await manifestCache.put('manifest', new Response(JSON.stringify(RESOURCES)));
+        return;
+      }
+      var oldManifest = await manifest.json();
+      var origin = self.location.origin;
+      for (var request of await contentCache.keys()) {
+        var key = request.url.substring(origin.length + 1);
+        if (key == "") {
+          key = "/";
+        }
+        // If a resource from the old manifest is not in the new cache, or if
+        // the MD5 sum has changed, delete it. Otherwise the resource is left
+        // in the cache and can be reused by the new service worker.
+        if (!RESOURCES[key] || RESOURCES[key] != oldManifest[key]) {
+          await contentCache.delete(request);
+        }
+      }
+      // Populate the cache with the app shell TEMP files, potentially overwriting
+      // cache files preserved above.
+      for (var request of await tempCache.keys()) {
+        var response = await tempCache.match(request);
+        await contentCache.put(request, response);
+      }
+      await caches.delete(TEMP);
+      // Save the manifest to make future upgrades efficient.
+      await manifestCache.put('manifest', new Response(JSON.stringify(RESOURCES)));
+      return;
+    } catch (err) {
+      // On an unhandled exception the state of the cache cannot be guaranteed.
+      console.error('Failed to upgrade service worker: ' + err);
+      await caches.delete(CACHE_NAME);
+      await caches.delete(TEMP);
+      await caches.delete(MANIFEST);
+    }
+  }());
+});
+
+// The fetch handler redirects requests for RESOURCE files to the service
+// worker cache.
+self.addEventListener("fetch", (event) => {
+  if (event.request.method !== 'GET') {
+    return;
+  }
+  var origin = self.location.origin;
+  var key = event.request.url.substring(origin.length + 1);
+  // Redirect URLs to the index.html
+  if (key.indexOf('?v=') != -1) {
+    key = key.split('?v=')[0];
+  }
+  if (event.request.url == origin || event.request.url.startsWith(origin + '/#') || key == '') {
+    key = '/';
+  }
+  // If the URL is not the RESOURCE list then return to signal that the
+  // browser should take over.
+  if (!RESOURCES[key]) {
+    return;
+  }
+  // If the URL is the index.html, perform an online-first request.
+  if (key == '/') {
+    return onlineFirst(event);
+  }
+  event.respondWith(caches.open(CACHE_NAME)
+    .then((cache) =>  {
+      return cache.match(event.request).then((response) => {
+        // Either respond with the cached resource, or perform a fetch and
+        // lazily populate the cache.
+        return response || fetch(event.request).then((response) => {
+          cache.put(event.request, response.clone());
+          return response;
+        });
+      })
+    })
+  );
+});
+
+self.addEventListener('message', (event) => {
+  // SkipWaiting can be used to immediately activate a waiting service worker.
+  // This will also require a page refresh triggered by the main worker.
+  if (event.data === 'skipWaiting') {
+    self.skipWaiting();
+    return;
+  }
+  if (event.data === 'downloadOffline') {
+    downloadOffline();
+    return;
+  }
+});
+
+// Download offline will check the RESOURCES for all files not in the cache
+// and populate them.
+async function downloadOffline() {
+  var resources = [];
+  var contentCache = await caches.open(CACHE_NAME);
+  var currentContent = {};
+  for (var request of await contentCache.keys()) {
+    var key = request.url.substring(origin.length + 1);
+    if (key == "") {
+      key = "/";
+    }
+    currentContent[key] = true;
+  }
+  for (var resourceKey of Object.keys(RESOURCES)) {
+    if (!currentContent[resourceKey]) {
+      resources.push(resourceKey);
+    }
+  }
+  return contentCache.addAll(resources);
+}
+
+// Attempt to download the resource online before falling back to
+// the offline cache.
+function onlineFirst(event) {
+  return event.respondWith(
+    fetch(event.request).then((response) => {
+      return caches.open(CACHE_NAME).then((cache) => {
+        cache.put(event.request, response.clone());
+        return response;
+      });
+    }).catch((error) => {
+      return caches.open(CACHE_NAME).then((cache) => {
+        return cache.match(event.request).then((response) => {
+          if (response != null) {
+            return response;
+          }
+          throw error;
+        });
+      });
+    })
+  );
+}
+''';
+}

packages/flutter_tools/lib/src/web/file_generators/main_dart.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:package_config/package_config.dart';
+
+/// Generates the main.dart file.
+String generateMainDartFile(String appEntrypoint, {
+  required String pluginRegistrantEntrypoint,
+  LanguageVersion? languageVersion,
+}) {
+  return <String>[
+    if (languageVersion != null)
+      '// @dart=${languageVersion.major}.${languageVersion.minor}',
+    '// Flutter web bootstrap script for $appEntrypoint.',
+    '//',
+    '// Generated file. Do not edit.',
+    '//',
+    '',
+    '// ignore_for_file: type=lint',
+    '',
+    "import 'dart:ui' as ui;",
+    "import 'dart:async';",
+    '',
+    "import '$appEntrypoint' as entrypoint;",
+    "import '$pluginRegistrantEntrypoint' as pluginRegistrant;",
+    '',
+    'typedef _UnaryFunction = dynamic Function(List<String> args);',
+    'typedef _NullaryFunction = dynamic Function();',
+    '',
+    'Future<void> main() async {',
+    '  await ui.webOnlyWarmupEngine(',
+    '    runApp: () {',
+    '      if (entrypoint.main is _UnaryFunction) {',
+    '        return (entrypoint.main as _UnaryFunction)(<String>[]);',
+    '      }',
+    '      return (entrypoint.main as _NullaryFunction)();',
+    '    },',
+    '    registerPlugins: () {',
+    '      pluginRegistrant.registerPlugins();',
+    '    },',
+    '  );',
+    '}',
+    '',
+  ].join('\n');
+}

packages/flutter_tools/lib/src/web/migrations/scrub_generated_plugin_registrant.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import '../../base/file_system.dart';
+import '../../base/logger.dart';
+import '../../base/project_migrator.dart';
+import '../../project.dart';
+
+/// Remove lib/generated_plugin_registrant.dart if it exists.
+class ScrubGeneratedPluginRegistrant extends ProjectMigrator {
+  ScrubGeneratedPluginRegistrant(
+    WebProject project,
+    super.logger,
+  ) : _project = project, _logger = logger;
+
+  final WebProject _project;
+  final Logger _logger;
+
+  @override
+  bool migrate() {
+    final File registrant = _project.libDirectory.childFile('generated_plugin_registrant.dart');
+    final File gitignore = _project.parent.directory.childFile('.gitignore');
+
+    if (!removeFile(registrant)) {
+      return false;
+    }
+    if (gitignore.existsSync()) {
+      processFileLines(gitignore);
+    }
+    return true;
+  }
+
+  // Cleans up the .gitignore by removing the line that mentions generated_plugin_registrant.
+  @override
+  String? migrateLine(String line) {
+    return line.contains('lib/generated_plugin_registrant.dart') ? null : line;
+  }
+
+  bool removeFile(File file) {
+    if (!file.existsSync()) {
+      _logger.printTrace('${file.basename} not found. Skipping.');
+      return true;
+    }
+
+    try {
+      file.deleteSync();
+      _logger.printStatus('${file.basename} found. Deleted.');
+      return true;
+    } on FileSystemException catch (e, s) {
+      _logger.printError(e.message, stackTrace: s);
+    }
+
+    return false;
+  }
+}

packages/flutter_tools/templates/app_shared/.gitignore.tmpl

@@ -32,9 +32,6 @@ migrate_working_dir/
 .pub/
 /build/
 
-# Web related
-lib/generated_plugin_registrant.dart
-
 # Symbolication related
 app.*.symbols
 

packages/flutter_tools/test/commands.shard/hermetic/build_web_test.dart

@@ -92,7 +92,9 @@ void main() {
     setupFileSystemForEndToEndTest(fileSystem);
     await runner.run(<String>['build', 'web', '--no-pub', '--dart-define=foo=a', '--dart2js-optimization=O3']);
 
-    expect(fileSystem.file(fileSystem.path.join('lib', 'generated_plugin_registrant.dart')).existsSync(), true);
+    final Directory buildDir = fileSystem.directory(fileSystem.path.join('build', 'web'));
+
+    expect(buildDir.existsSync(), true);
   }, overrides: <Type, Generator>{
     Platform: () => fakePlatform,
     FileSystem: () => fileSystem,

packages/flutter_tools/test/general.shard/build_system/targets/web_test.dart

@@ -8,12 +8,15 @@ import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/artifacts.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/platform.dart';
+import 'package:flutter_tools/src/base/template.dart';
 import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/build_system/build_system.dart';
 import 'package:flutter_tools/src/build_system/depfile.dart';
 import 'package:flutter_tools/src/build_system/targets/web.dart';
 import 'package:flutter_tools/src/globals.dart' as globals;
-import 'package:flutter_tools/src/web/flutter_js.dart' as flutter_js;
+import 'package:flutter_tools/src/isolated/mustache_template.dart';
+import 'package:flutter_tools/src/web/file_generators/flutter_js.dart' as flutter_js;
+import 'package:flutter_tools/src/web/file_generators/flutter_service_worker_js.dart';
 
 import '../../../src/common.dart';
 import '../../../src/fake_process_manager.dart';
@@ -80,8 +83,8 @@ void main() {
     final String generated = environment.buildDir.childFile('main.dart').readAsStringSync();
 
     // Plugins
-    expect(generated, contains("import 'package:foo/generated_plugin_registrant.dart';"));
-    expect(generated, contains('registerPlugins(webPluginRegistrar);'));
+    expect(generated, contains("import 'web_plugin_registrant.dart' as pluginRegistrant;"));
+    expect(generated, contains('pluginRegistrant.registerPlugins();'));
 
     // Import.
     expect(generated, contains("import 'package:foo/main.dart' as entrypoint;"));
@@ -89,6 +92,8 @@ void main() {
     // Main
     expect(generated, contains('ui.webOnlyWarmupEngine('));
     expect(generated, contains('entrypoint.main as _'));
+  }, overrides: <Type, Generator>{
+    TemplateRenderer: () => const MustacheTemplateRenderer(),
   }));
 
   test('version.json is created after release build', () => testbed.run(() async {
@@ -196,6 +201,8 @@ void main() {
 
     // Import.
     expect(generated, contains("import 'file:///other/lib/main.dart' as entrypoint;"));
+  }, overrides: <Type, Generator>{
+    TemplateRenderer: () => const MustacheTemplateRenderer(),
   }));
 
   test('WebEntrypointTarget generates a plugin registrant for a file outside of main', () => testbed.run(() async {
@@ -210,7 +217,9 @@ void main() {
 
     // Import.
     expect(generated, contains("import 'file:///other/lib/main.dart' as entrypoint;"));
-    expect(generated, contains("import 'package:foo/generated_plugin_registrant.dart';"));
+    expect(generated, contains("import 'web_plugin_registrant.dart' as pluginRegistrant;"));
+  }, overrides: <Type, Generator>{
+    TemplateRenderer: () => const MustacheTemplateRenderer(),
   }));
 
 
@@ -226,8 +235,8 @@ void main() {
     final String generated = environment.buildDir.childFile('main.dart').readAsStringSync();
 
     // Plugins
-    expect(generated, contains("import 'package:foo/generated_plugin_registrant.dart';"));
-    expect(generated, contains('registerPlugins(webPluginRegistrar);'));
+    expect(generated, contains("import 'web_plugin_registrant.dart' as pluginRegistrant;"));
+    expect(generated, contains('pluginRegistrant.registerPlugins();'));
 
     // Import.
     expect(generated, contains("import 'package:foo/main.dart' as entrypoint;"));
@@ -237,6 +246,7 @@ void main() {
     expect(generated, contains('entrypoint.main as _'));
   }, overrides: <Type, Generator>{
     Platform: () => windows,
+    TemplateRenderer: () => const MustacheTemplateRenderer(),
   }));
 
   test('WebEntrypointTarget generates an entrypoint without plugins and init platform', () => testbed.run(() async {
@@ -249,9 +259,9 @@ void main() {
 
     final String generated = environment.buildDir.childFile('main.dart').readAsStringSync();
 
-    // Plugins
-    expect(generated, isNot(contains("import 'package:foo/generated_plugin_registrant.dart';")));
-    expect(generated, isNot(contains('registerPlugins(webPluginRegistrar);')));
+    // Plugins (the generated file is a noop)
+    expect(generated, contains("import 'web_plugin_registrant.dart' as pluginRegistrant;"));
+    expect(generated, contains('pluginRegistrant.registerPlugins();'));
 
     // Import.
     expect(generated, contains("import 'package:foo/main.dart' as entrypoint;"));
@@ -259,7 +269,8 @@ void main() {
     // Main
     expect(generated, contains('ui.webOnlyWarmupEngine('));
     expect(generated, contains('entrypoint.main as _'));
-
+  }, overrides: <Type, Generator>{
+    TemplateRenderer: () => const MustacheTemplateRenderer(),
   }));
 
   test('WebEntrypointTarget generates an entrypoint with a language version', () => testbed.run(() async {
@@ -273,6 +284,8 @@ void main() {
 
     // Language version
     expect(generated, contains('// @dart=2.8'));
+  }, overrides: <Type, Generator>{
+    TemplateRenderer: () => const MustacheTemplateRenderer(),
   }));
 
   test('WebEntrypointTarget generates an entrypoint with a language version from a package config', () => testbed.run(() async {
@@ -288,6 +301,8 @@ void main() {
 
     // Language version
     expect(generated, contains('// @dart=2.7'));
+  }, overrides: <Type, Generator>{
+    TemplateRenderer: () => const MustacheTemplateRenderer(),
   }));
 
   test('WebEntrypointTarget generates an entrypoint without plugins and without init platform', () => testbed.run(() async {
@@ -301,8 +316,8 @@ void main() {
     final String generated = environment.buildDir.childFile('main.dart').readAsStringSync();
 
     // Plugins
-    expect(generated, isNot(contains("import 'package:foo/generated_plugin_registrant.dart';")));
-    expect(generated, isNot(contains('registerPlugins(webPluginRegistrar);')));
+    expect(generated, contains("import 'web_plugin_registrant.dart' as pluginRegistrant;"));
+    expect(generated, contains('pluginRegistrant.registerPlugins();'));
 
     // Import.
     expect(generated, contains("import 'package:foo/main.dart' as entrypoint;"));
@@ -310,6 +325,8 @@ void main() {
     // Main
     expect(generated, contains('ui.webOnlyWarmupEngine('));
     expect(generated, contains('entrypoint.main as _'));
+  }, overrides: <Type, Generator>{
+    TemplateRenderer: () => const MustacheTemplateRenderer(),
   }));
 
   test('Dart2JSTarget calls dart2js with expected args with csp', () => testbed.run(() async {
@@ -676,9 +693,9 @@ void main() {
     // Depends on resource file.
     expect(environment.buildDir.childFile('service_worker.d').readAsStringSync(),
       contains('a/a.txt'));
-    // Contains NOTICES
+    // Does NOT contain NOTICES
     expect(environment.outputDir.childFile('flutter_service_worker.js').readAsStringSync(),
-      contains('NOTICES'));
+      isNot(contains('NOTICES')));
   }));
 
   test('WebServiceWorker contains baseUrl cache', () => testbed.run(() async {

packages/flutter_tools/test/general.shard/plugins_test.dart

@@ -1079,11 +1079,12 @@ dependencies:
 web_plugin_with_nested:${webPluginWithNestedFile.childDirectory('lib').uri}
 ''');
 
-        await injectPlugins(flutterProject, webPlatform: true);
+        final Directory destination = flutterProject.directory.childDirectory('lib');
+        await injectBuildTimePluginFiles(flutterProject, webPlatform: true, destination: destination);
 
         final File registrant = flutterProject.directory
             .childDirectory('lib')
-            .childFile('generated_plugin_registrant.dart');
+            .childFile('web_plugin_registrant.dart');
 
         expect(registrant.existsSync(), isTrue);
         expect(registrant.readAsStringSync(), contains("import 'package:web_plugin_with_nested/src/web_plugin.dart';"));

packages/flutter_tools/test/general.shard/web/migrations/scrub_generated_plugin_registrant_test.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// @dart = 2.8
+
+import 'package:file/memory.dart';
+import 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/build_system/build_system.dart';
+import 'package:flutter_tools/src/cache.dart';
+import 'package:flutter_tools/src/commands/build.dart';
+
+import '../../../src/context.dart'; // legacy
+import '../../../src/test_build_system.dart';
+import '../../../src/test_flutter_command_runner.dart'; // legacy
+
+void main() {
+  setUpAll(() {
+    Cache.flutterRoot = '';
+    Cache.disableLocking();
+  });
+
+  group('ScrubGeneratedPluginRegistrant', () {
+    // The files this migration deals with
+    File gitignore;
+    File registrant;
+
+    // Environment overrides
+    FileSystem fileSystem;
+    ProcessManager processManager;
+    BuildSystem buildSystem;
+
+    setUp(() {
+      // Prepare environment overrides
+      fileSystem = MemoryFileSystem.test();
+      processManager = FakeProcessManager.any();
+      buildSystem = TestBuildSystem.all(BuildResult(success: true));
+      // Write some initial state into our testing filesystem
+      setupFileSystemForEndToEndTest(fileSystem);
+      // Initialize fileSystem references
+      gitignore = fileSystem.file('.gitignore');
+      registrant = fileSystem.file(fileSystem.path.join('lib', 'generated_plugin_registrant.dart'));
+    });
+
+    testUsingContext('noop - nothing to do - build runs', () async {
+      expect(gitignore.existsSync(), isFalse);
+      expect(registrant.existsSync(), isFalse);
+
+      await createTestCommandRunner(BuildCommand())
+          .run(<String>['build', 'web', '--no-pub']);
+
+      final Directory buildDir = fileSystem.directory(fileSystem.path.join('build', 'web'));
+      expect(buildDir.existsSync(), true);
+    }, overrides: <Type, Generator> {
+      FileSystem: () => fileSystem,
+      ProcessManager: () => processManager,
+      BuildSystem: () => buildSystem,
+    });
+
+    testUsingContext('noop - .gitignore does not reference generated_plugin_registrant.dart - untouched', () async {
+      writeGitignore(fileSystem, mentionsPluginRegistrant: false);
+
+      final String contentsBeforeBuild = gitignore.readAsStringSync();
+      expect(contentsBeforeBuild, isNot(contains('lib/generated_plugin_registrant.dart')));
+
+      await createTestCommandRunner(BuildCommand())
+          .run(<String>['build', 'web', '--no-pub']);
+
+      expect(gitignore.readAsStringSync(), contentsBeforeBuild);
+    }, overrides: <Type, Generator> {
+      FileSystem: () => fileSystem,
+      ProcessManager: () => processManager,
+      BuildSystem: () => buildSystem,
+    });
+
+    testUsingContext('.gitignore references generated_plugin_registrant - cleans it up', () async {
+      writeGitignore(fileSystem);
+
+      expect(gitignore.existsSync(), isTrue);
+      expect(gitignore.readAsStringSync(), contains('lib/generated_plugin_registrant.dart'));
+
+      await createTestCommandRunner(BuildCommand())
+          .run(<String>['build', 'web', '--no-pub']);
+
+      expect(gitignore.readAsStringSync(), isNot(contains('lib/generated_plugin_registrant.dart')));
+    }, overrides: <Type, Generator> {
+      FileSystem: () => fileSystem,
+      ProcessManager: () => processManager,
+      BuildSystem: () => buildSystem,
+    });
+
+    testUsingContext('generated_plugin_registrant.dart exists - gets deleted', () async {
+      writeGeneratedPluginRegistrant(fileSystem);
+
+      expect(registrant.existsSync(), isTrue);
+
+      await createTestCommandRunner(BuildCommand())
+          .run(<String>['build', 'web', '--no-pub']);
+
+      expect(registrant.existsSync(), isFalse);
+    }, overrides: <Type, Generator> {
+      FileSystem: () => fileSystem,
+      ProcessManager: () => processManager,
+      BuildSystem: () => buildSystem,
+    });
+
+    testUsingContext('scrubs generated_plugin_registrant file and cleans .gitignore', () async {
+      writeGitignore(fileSystem);
+      writeGeneratedPluginRegistrant(fileSystem);
+
+      expect(registrant.existsSync(), isTrue);
+      expect(gitignore.readAsStringSync(), contains('lib/generated_plugin_registrant.dart'));
+
+      await createTestCommandRunner(BuildCommand())
+          .run(<String>['build', 'web', '--no-pub']);
+
+      expect(registrant.existsSync(), isFalse);
+      expect(gitignore.readAsStringSync(), isNot(contains('lib/generated_plugin_registrant.dart')));
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fileSystem,
+      ProcessManager: () => processManager,
+      BuildSystem: () => buildSystem,
+    });
+  });
+}
+
+// Writes something that resembles the contents of Flutter's .gitignore file
+void writeGitignore(FileSystem fs, { bool mentionsPluginRegistrant = true }) {
+  fs.file('.gitignore').createSync(recursive: true);
+  fs.file('.gitignore')
+      .writeAsStringSync('''
+/build/
+
+# Web related
+${mentionsPluginRegistrant ? 'lib/generated_plugin_registrant.dart':'another_file.dart'}
+
+# Symbolication related
+''');
+}
+
+// Creates an empty generated_plugin_registrant.dart file
+void writeGeneratedPluginRegistrant(FileSystem fs) {
+  final String path = fs.path.join('lib', 'generated_plugin_registrant.dart');
+  fs.file(path).createSync(recursive: true);
+}
+
+// Adds a bunch of files to the filesystem
+// (taken from commands.shard/hermetic/build_web_test.dart)
+void setupFileSystemForEndToEndTest(FileSystem fileSystem) {
+  final List<String> dependencies = <String>[
+    '.packages',
+    fileSystem.path.join('web', 'index.html'),
+    fileSystem.path.join('lib', 'main.dart'),
+    fileSystem.path.join('packages', 'flutter_tools', 'lib', 'src', 'build_system', 'targets', 'web.dart'),
+    fileSystem.path.join('bin', 'cache', 'flutter_web_sdk'),
+    fileSystem.path.join('bin', 'cache', 'dart-sdk', 'bin', 'snapshots', 'dart2js.dart.snapshot'),
+    fileSystem.path.join('bin', 'cache', 'dart-sdk', 'bin', 'dart'),
+    fileSystem.path.join('bin', 'cache', 'dart-sdk '),
+  ];
+  for (final String dependency in dependencies) {
+    fileSystem.file(dependency).createSync(recursive: true);
+  }
+
+  // Project files.
+  fileSystem.file('.packages')
+      .writeAsStringSync('''
+foo:lib/
+fizz:bar/lib/
+''');
+  fileSystem.file('pubspec.yaml')
+      .writeAsStringSync('''
+name: foo
+
+dependencies:
+  flutter:
+    sdk: flutter
+  fizz:
+    path:
+      bar/
+''');
+  fileSystem.file(fileSystem.path.join('bar', 'pubspec.yaml'))
+    ..createSync(recursive: true)
+    ..writeAsStringSync('''
+name: bar
+
+flutter:
+  plugin:
+    platforms:
+      web:
+        pluginClass: UrlLauncherPlugin
+        fileName: url_launcher_web.dart
+''');
+  fileSystem.file(fileSystem.path.join('bar', 'lib', 'url_launcher_web.dart'))
+    ..createSync(recursive: true)
+    ..writeAsStringSync('''
+class UrlLauncherPlugin {}
+''');
+  fileSystem.file(fileSystem.path.join('lib', 'main.dart'))
+      .writeAsStringSync('void main() { }');
+}

packages/flutter_tools/test/integration.shard/generated_plugin_registrant_test.dart → packages/flutter_tools/test/integration.shard/web_plugin_registrant_test.dart

@@ -49,12 +49,20 @@ void main() {
     // the generated_plugin_registrant generation.
     await _addDependency(projectDir, 'shared_preferences',
         version: '^2.0.0');
-    await _analyzeProject(projectDir);
+    // The plugin registrant is only created after a build...
+    await _buildWebProject(projectDir);
+
+    // Find the web_plugin_registrant, now that it lives outside "lib":
+    final Directory buildDir = projectDir
+        .childDirectory('.dart_tool/flutter_build')
+        .listSync()
+        .firstWhere((FileSystemEntity entity) => entity is Directory) as Directory;
 
     expect(
-      projectDir.childFile('lib/generated_plugin_registrant.dart'),
+      buildDir.childFile('web_plugin_registrant.dart'),
       exists,
     );
+    await _analyzeEntity(buildDir.childFile('web_plugin_registrant.dart'));
   }, overrides: <Type, Generator>{
     Pub: () => Pub(
           fileSystem: globals.fs,
@@ -88,12 +96,20 @@ void main() {
       'test_web_plugin_with_a_purposefully_extremely_long_package_name',
       path: '../test_plugin',
     );
-    await _analyzeProject(projectDir);
+    // The plugin registrant is only created after a build...
+    await _buildWebProject(projectDir);
+
+    // Find the web_plugin_registrant, now that it lives outside "lib":
+    final Directory buildDir = projectDir
+        .childDirectory('.dart_tool/flutter_build')
+        .listSync()
+        .firstWhere((FileSystemEntity entity) => entity is Directory) as Directory;
 
     expect(
-      projectDir.childFile('lib/generated_plugin_registrant.dart'),
+      buildDir.childFile('web_plugin_registrant.dart'),
       exists,
     );
+    await _analyzeEntity(buildDir.childFile('web_plugin_registrant.dart'));
   }, overrides: <Type, Generator>{
     Pub: () => Pub(
           fileSystem: globals.fs,
@@ -215,7 +231,7 @@ ${linterRules.map((String rule) => '    - $rule').join('\n')}
   ''');
 }
 
-Future<void> _analyzeProject(Directory workingDir) async {
+Future<void> _analyzeEntity(FileSystemEntity target) async {
   final String flutterToolsSnapshotPath = globals.fs.path.absolute(
     globals.fs.path.join(
       '..',
@@ -229,15 +245,44 @@ Future<void> _analyzeProject(Directory workingDir) async {
   final List<String> args = <String>[
     flutterToolsSnapshotPath,
     'analyze',
+    target.path,
   ];
 
   final ProcessResult exec = await Process.run(
     globals.artifacts.getHostArtifact(HostArtifact.engineDartBinary).path,
     args,
-    workingDirectory: workingDir.path,
+    workingDirectory: target is Directory ? target.path : target.dirname,
   );
   printOnFailure('Output of flutter analyze:');
   printOnFailure(exec.stdout.toString());
   printOnFailure(exec.stderr.toString());
   expect(exec.exitCode, 0);
 }
+
+Future<void> _buildWebProject(Directory workingDir) async {
+  final String flutterToolsSnapshotPath = globals.fs.path.absolute(
+    globals.fs.path.join(
+      '..',
+      '..',
+      'bin',
+      'cache',
+      'flutter_tools.snapshot',
+    ),
+  );
+
+  final List<String> args = <String>[
+    flutterToolsSnapshotPath,
+    'build',
+    'web',
+  ];
+
+  final ProcessResult exec = await Process.run(
+    globals.artifacts.getHostArtifact(HostArtifact.engineDartBinary).path,
+    args,
+    workingDirectory: workingDir.path,
+  );
+  printOnFailure('Output of flutter build web:');
+  printOnFailure(exec.stdout.toString());
+  printOnFailure(exec.stderr.toString());
+  expect(exec.exitCode, 0);
+}