[flutter_tools] Generate Localizations on `flutter run` for web (#110526)

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

@@ -280,6 +280,7 @@ class ResidentWebRunner extends ResidentRunner {
         );
         final Uri url = await device!.devFS!.create();
         if (debuggingOptions.buildInfo.isDebug) {
+          await runSourceGenerators();
           final UpdateFSReport report = await _updateDevFS(fullRestart: true);
           if (!report.success) {
             _logger!.printError('Failed to compile application.');

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

@@ -1388,6 +1388,47 @@ flutter:
     expect(testLogger.statusText, isEmpty);
   }));
 
+  testUsingContext('ResidentRunner generates files when l10n.yaml exists', () => testbed.run(() async {
+    globals.fs.file(globals.fs.path.join('lib', 'main.dart'))
+      .createSync(recursive: true);
+    final File arbFile = globals.fs.file(globals.fs.path.join('lib', 'l10n', 'app_en.arb'))
+      ..createSync(recursive: true);
+    arbFile.writeAsStringSync('''
+{
+  "helloWorld": "Hello, World!",
+  "@helloWorld": {
+    "description": "Sample description"
+  }
+}''');
+    globals.fs.file('l10n.yaml').createSync();
+    globals.fs.file('pubspec.yaml').writeAsStringSync('flutter:\n  generate: true\n');
+
+    fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[]);
+    final FakeResidentCompiler residentCompiler = FakeResidentCompiler()
+      ..nextOutput = const CompilerOutput('foo', 1 ,<Uri>[]);
+    residentRunner = HotRunner(
+      <FlutterDevice>[
+        flutterDevice,
+      ],
+      stayResident: false,
+      debuggingOptions: DebuggingOptions.enabled(BuildInfo.debug),
+      target: 'main.dart',
+      devtoolsHandler: createNoOpHandler,
+    );
+    flutterDevice.generator = residentCompiler;
+
+    await residentRunner.run();
+
+    final File generatedLocalizationsFile = globals.fs.directory('.dart_tool')
+      .childDirectory('flutter_gen')
+      .childDirectory('gen_l10n')
+      .childFile('app_localizations.dart');
+    expect(generatedLocalizationsFile.existsSync(), isTrue);
+
+    // Completing this future ensures that the daemon can exit correctly.
+    expect(await residentRunner.waitForAppToFinish(), 1);
+  }));
+
   testUsingContext('ResidentRunner printHelpDetails hot runner', () => testbed.run(() {
     fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[]);
 

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

@@ -1049,6 +1049,69 @@ void main() {
     ProcessManager: () => processManager,
   });
 
+  testUsingContext('ResidentWebRunner generates files when l10n.yaml exists', () async {
+    fakeVmServiceHost =
+        FakeVmServiceHost(requests: kAttachExpectations.toList());
+    setupMocks();
+    final ResidentRunner residentWebRunner = ResidentWebRunner(
+      flutterDevice,
+      flutterProject:
+          FlutterProject.fromDirectoryTest(fileSystem.currentDirectory),
+      debuggingOptions: DebuggingOptions.enabled(BuildInfo.debug),
+      ipv6: true,
+      stayResident: false,
+      fileSystem: fileSystem,
+      logger: BufferLogger.test(),
+      usage: globals.flutterUsage,
+      systemClock: globals.systemClock,
+    );
+
+    // Create necessary files.
+    globals.fs.file(globals.fs.path.join('lib', 'main.dart'))
+      .createSync(recursive: true);
+    globals.fs.file(globals.fs.path.join('lib', 'l10n', 'app_en.arb'))
+      ..createSync(recursive: true)
+      ..writeAsStringSync('''
+{
+  "helloWorld": "Hello, World!",
+  "@helloWorld": {
+    "description": "Sample description"
+  }
+}''');
+    globals.fs.file('l10n.yaml').createSync();
+    globals.fs.file('pubspec.yaml').writeAsStringSync('''
+flutter:
+  generate: true
+''');
+    globals.fs.directory('.dart_tool')
+      .childFile('package_config.json')
+      ..createSync(recursive: true)
+      ..writeAsStringSync('''
+{
+  "configVersion": 2,
+  "packages": [
+    {
+      "name": "path_provider_linux",
+      "rootUri": "../../../path_provider_linux",
+      "packageUri": "lib/",
+      "languageVersion": "2.12"
+    }
+  ]
+}
+''');
+    expect(await residentWebRunner.run(), 0);
+    final File generatedLocalizationsFile = globals.fs.directory('.dart_tool')
+      .childDirectory('flutter_gen')
+      .childDirectory('gen_l10n')
+      .childFile('app_localizations.dart');
+    expect(generatedLocalizationsFile.existsSync(), isTrue);
+    // Completing this future ensures that the daemon can exit correctly.
+    expect(fakeVmServiceHost.hasRemainingExpectations, false);
+  }, overrides: <Type, Generator>{
+    FileSystem: () => fileSystem,
+    ProcessManager: () => processManager,
+  });
+
   // While this file should be ignored on web, generating it here will cause a
   // perf regression in hot restart.
   testUsingContext('Does not generate dart_plugin_registrant.dart', () async {