Remove the fast reassemble / single widget reload feature (#132255)

Fixes https://github.com/flutter/flutter/issues/132157

packages/flutter/lib/src/foundation/binding.dart

@@ -168,13 +168,6 @@ abstract class BindingBase {
   static Type? _debugInitializedType;
   static bool _debugServiceExtensionsRegistered = false;
 
-  /// Additional configuration used by the framework during hot reload.
-  ///
-  /// See also:
-  ///
-  ///  * [DebugReassembleConfig], which describes the configuration.
-  static DebugReassembleConfig? debugReassembleConfig;
-
   /// Deprecated. Will be removed in a future version of Flutter.
   ///
   /// This property has been deprecated to prepare for Flutter's upcoming
@@ -989,23 +982,3 @@ abstract class BindingBase {
 Future<void> _exitApplication() async {
   exit(0);
 }
-
-/// Additional configuration used for hot reload reassemble optimizations.
-///
-/// Do not extend, implement, or mixin this class. This may only be instantiated
-/// in debug mode.
-class DebugReassembleConfig {
-  /// Create a new [DebugReassembleConfig].
-  ///
-  /// Throws a [FlutterError] if this is called in profile or release mode.
-  DebugReassembleConfig({
-    this.widgetName,
-  }) {
-    if (!kDebugMode) {
-      throw FlutterError('Cannot instantiate DebugReassembleConfig in profile or release mode.');
-    }
-  }
-
-  /// The name of the widget that was modified, or `null` if the change was elsewhere.
-  final String? widgetName;
-}

packages/flutter/lib/src/rendering/binding.dart

@@ -603,7 +603,6 @@ mixin RendererBinding on BindingBase, ServicesBinding, SchedulerBinding, Gesture
   @override
   Future<void> performReassemble() async {
     await super.performReassemble();
-    if (BindingBase.debugReassembleConfig?.widgetName == null) {
     if (!kReleaseMode) {
       FlutterTimeline.startSync('Preparing Hot Reload (layout)');
     }
@@ -616,7 +615,6 @@ mixin RendererBinding on BindingBase, ServicesBinding, SchedulerBinding, Gesture
         FlutterTimeline.finishSync();
       }
     }
-    }
     scheduleWarmUpFrame();
     await endOfFrame;
   }

packages/flutter/lib/src/widgets/binding.dart

@@ -505,23 +505,6 @@ mixin WidgetsBinding on BindingBase, ServicesBinding, SchedulerBinding, GestureB
         },
       );
 
-      registerServiceExtension(
-        name: WidgetsServiceExtensions.fastReassemble.name,
-        callback: (Map<String, Object> params) async {
-          // This mirrors the implementation of the 'reassemble' callback registration
-          // in lib/src/foundation/binding.dart, but with the extra binding config used
-          // to skip some reassemble work.
-          final String? className = params['className'] as String?;
-          BindingBase.debugReassembleConfig = DebugReassembleConfig(widgetName: className);
-          try {
-            await reassembleApplication();
-          } finally {
-            BindingBase.debugReassembleConfig = null;
-          }
-          return <String, String>{'type': 'Success'};
-        },
-      );
-
       // Expose the ability to send Widget rebuilds as [Timeline] events.
       registerBoolServiceExtension(
         name: WidgetsServiceExtensions.profileWidgetBuilds.name,
@@ -560,7 +543,7 @@ mixin WidgetsBinding on BindingBase, ServicesBinding, SchedulerBinding, GestureB
 
   Future<void> _forceRebuild() {
     if (rootElement != null) {
-      buildOwner!.reassemble(rootElement!, null);
+      buildOwner!.reassemble(rootElement!);
       return endOfFrame;
     }
     return Future<void>.value();
@@ -1090,7 +1073,7 @@ mixin WidgetsBinding on BindingBase, ServicesBinding, SchedulerBinding, GestureB
     }());
 
     if (rootElement != null) {
-      buildOwner!.reassemble(rootElement!, BindingBase.debugReassembleConfig);
+      buildOwner!.reassemble(rootElement!);
     }
     return super.performReassemble();
   }

packages/flutter/lib/src/widgets/framework.dart

@@ -3252,14 +3252,13 @@ class BuildOwner {
   /// changed implementations.
   ///
   /// This is expensive and should not be called except during development.
-  void reassemble(Element root, DebugReassembleConfig? reassembleConfig) {
+  void reassemble(Element root) {
     if (!kReleaseMode) {
       FlutterTimeline.startSync('Preparing Hot Reload (widgets)');
     }
     try {
       assert(root._parent == null);
       assert(root.owner == this);
-      root._debugReassembleConfig = reassembleConfig;
       root.reassemble();
     } finally {
       if (!kReleaseMode) {
@@ -3374,7 +3373,6 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
   }
 
   Element? _parent;
-  DebugReassembleConfig? _debugReassembleConfig;
   _NotificationNode? _notificationTree;
 
   /// Compare two widgets for equality.
@@ -3526,15 +3524,10 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
   @mustCallSuper
   @protected
   void reassemble() {
-    if (_debugShouldReassemble(_debugReassembleConfig, _widget)) {
     markNeedsBuild();
-      _debugReassembleConfig = null;
-    }
     visitChildren((Element child) {
-      child._debugReassembleConfig = _debugReassembleConfig;
       child.reassemble();
     });
-    _debugReassembleConfig = null;
   }
 
   bool _debugIsInScope(Element target) {
@@ -5585,9 +5578,7 @@ class StatefulElement extends ComponentElement {
 
   @override
   void reassemble() {
-    if (_debugShouldReassemble(_debugReassembleConfig, _widget)) {
     state.reassemble();
-    }
     super.reassemble();
   }
 
@@ -6952,9 +6943,3 @@ class _NullWidget extends Widget {
   @override
   Element createElement() => throw UnimplementedError();
 }
-
-// Whether a [DebugReassembleConfig] indicates that an element holding [widget] can skip
-// a reassemble.
-bool _debugShouldReassemble(DebugReassembleConfig? config, Widget? widget) {
-  return config == null || config.widgetName == null || widget?.runtimeType.toString() == config.widgetName;
-}

packages/flutter/lib/src/widgets/widget_inspector.dart

@@ -970,7 +970,7 @@ mixin WidgetInspectorService {
   Future<void> forceRebuild() {
     final WidgetsBinding binding = WidgetsBinding.instance;
     if (binding.rootElement != null) {
-      binding.buildOwner!.reassemble(binding.rootElement!, null);
+      binding.buildOwner!.reassemble(binding.rootElement!);
       return binding.endOfFrame;
     }
     return Future<void>.value();

packages/flutter/test/foundation/service_extensions_test.dart

@@ -116,6 +116,7 @@ Future<Map<String, dynamic>> hasReassemble(Future<Map<String, dynamic>> pendingR
 }
 
 void main() {
+  final Set<String> testedExtensions = <String>{}; // Add the name of an extension to this set in the test where it is tested.
   final List<String?> console = <String?>[];
   late PipelineOwner owner;
 
@@ -153,6 +154,9 @@ void main() {
 
     expect(binding.frameScheduled, isFalse);
 
+    testedExtensions.add(WidgetsServiceExtensions.didSendFirstFrameEvent.name);
+    testedExtensions.add(WidgetsServiceExtensions.didSendFirstFrameRasterizedEvent.name);
+
     expect(debugPrint, equals(debugPrintThrottled));
     debugPrint = (String? message, { int? wrapWidth }) {
       console.add(message);
@@ -162,12 +166,13 @@ void main() {
   tearDownAll(() async {
     // See widget_inspector_test.dart for tests of the ext.flutter.inspector
     // service extensions included in this count.
-    int widgetInspectorExtensionCount = 20;
+    int widgetInspectorExtensionCount = 28;
     if (WidgetInspectorService.instance.isWidgetCreationTracked()) {
       // Some inspector extensions are only exposed if widget creation locations
       // are tracked.
       widgetInspectorExtensionCount += 2;
     }
+    expect(binding.extensions.keys.where((String name) => name.startsWith('inspector.')), hasLength(widgetInspectorExtensionCount));
 
     // The following service extensions are disabled in web:
     // 1. exit
@@ -175,12 +180,13 @@ void main() {
     const int disabledExtensions = kIsWeb ? 2 : 0;
 
     // The expected number of registered service extensions in the Flutter
-    // framework, excluding any that are for the widget inspector
+    // framework, excluding any that are for the widget inspector (see
-    // (see widget_inspector_test.dart for tests of the ext.flutter.inspector
+    // widget_inspector_test.dart for tests of the ext.flutter.inspector service
-    // service extensions).
+    // extensions). Any test counted here must be tested in this file!
-    const int serviceExtensionCount = 38;
+    const int serviceExtensionCount = 29;
 
     expect(binding.extensions.length, serviceExtensionCount + widgetInspectorExtensionCount - disabledExtensions);
+    expect(testedExtensions, hasLength(serviceExtensionCount));
 
     expect(console, isEmpty);
     debugPrint = debugPrintThrottled;
@@ -213,6 +219,8 @@ void main() {
     expect(result, <String, String>{'enabled': 'true'});
     expect(WidgetsApp.debugAllowBannerOverride, true);
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(WidgetsServiceExtensions.debugAllowBanner.name);
   });
 
   test('Service extensions - debugDumpApp', () async {
@@ -221,6 +229,8 @@ void main() {
     expect(result, <String, dynamic>{
       'data': matches('TestServiceExtensionsBinding - DEBUG MODE\n<no tree currently mounted>'),
     });
+
+    testedExtensions.add(WidgetsServiceExtensions.debugDumpApp.name);
   });
 
   test('Service extensions - debugDumpFocusTree', () async {
@@ -234,6 +244,8 @@ void main() {
         r'$',
       ),
     });
+
+    testedExtensions.add(WidgetsServiceExtensions.debugDumpFocusTree.name);
   });
 
   test('Service extensions - debugDumpRenderTree', () async {
@@ -251,6 +263,8 @@ void main() {
         r'$',
       ),
     });
+
+    testedExtensions.add(RenderingServiceExtensions.debugDumpRenderTree.name);
   });
 
   test('Service extensions - debugDumpLayerTree', () async {
@@ -274,6 +288,8 @@ void main() {
         r'$',
       ),
     });
+
+    testedExtensions.add(RenderingServiceExtensions.debugDumpLayerTree.name);
   });
 
   test('Service extensions - debugDumpSemanticsTreeInTraversalOrder', () async {
@@ -288,6 +304,8 @@ void main() {
         r'To generate semantics, try turning on an assistive technology \(like VoiceOver or TalkBack\) on your device.'
       )
     });
+
+    testedExtensions.add(RenderingServiceExtensions.debugDumpSemanticsTreeInTraversalOrder.name);
   });
 
   test('Service extensions - debugDumpSemanticsTreeInInverseHitTestOrder', () async {
@@ -302,10 +320,12 @@ void main() {
         r'To generate semantics, try turning on an assistive technology \(like VoiceOver or TalkBack\) on your device.'
       )
     });
+
+    testedExtensions.add(RenderingServiceExtensions.debugDumpSemanticsTreeInInverseHitTestOrder.name);
   });
 
   test('Service extensions - debugPaint', () async {
-    final Iterable<Map<String, dynamic>> extensionChangedEvents = binding.getServiceExtensionStateChangedEvents('ext.flutter.debugPaint');
+    final Iterable<Map<String, dynamic>> extensionChangedEvents = binding.getServiceExtensionStateChangedEvents('ext.flutter.${RenderingServiceExtensions.debugPaint.name}');
     Map<String, dynamic> extensionChangedEvent;
     Map<String, dynamic> result;
     Future<Map<String, dynamic>> pendingResult;
@@ -357,6 +377,8 @@ void main() {
     expect(debugPaintSizeEnabled, false);
     expect(extensionChangedEvents.length, 2);
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(RenderingServiceExtensions.debugPaint.name);
   });
 
   test('Service extensions - debugPaintBaselinesEnabled', () async {
@@ -399,6 +421,8 @@ void main() {
     expect(result, <String, String>{'enabled': 'false'});
     expect(debugPaintBaselinesEnabled, false);
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(RenderingServiceExtensions.debugPaintBaselinesEnabled.name);
   });
 
   test('Service extensions - invertOversizedImages', () async {
@@ -445,6 +469,8 @@ void main() {
     expect(result, <String, String>{'enabled': 'false'});
     expect(debugInvertOversizedImages, false);
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(RenderingServiceExtensions.invertOversizedImages.name);
   });
 
   test('Service extensions - profileWidgetBuilds', () async {
@@ -474,6 +500,8 @@ void main() {
     expect(debugProfileBuildsEnabled, false);
 
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(WidgetsServiceExtensions.profileWidgetBuilds.name);
   });
 
   test('Service extensions - profileUserWidgetBuilds', () async {
@@ -503,6 +531,8 @@ void main() {
     expect(debugProfileBuildsEnabledUserWidgets, false);
 
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(WidgetsServiceExtensions.profileUserWidgetBuilds.name);
   });
 
   test('Service extensions - profileRenderObjectPaints', () async {
@@ -532,6 +562,8 @@ void main() {
     expect(debugProfilePaintsEnabled, false);
 
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(RenderingServiceExtensions.profileRenderObjectPaints.name);
   });
 
   test('Service extensions - profileRenderObjectLayouts', () async {
@@ -561,6 +593,8 @@ void main() {
     expect(debugProfileLayoutsEnabled, false);
 
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(RenderingServiceExtensions.profileRenderObjectLayouts.name);
   });
 
   test('Service extensions - evict', () async {
@@ -596,12 +630,16 @@ void main() {
     expect(data, isFalse);
     expect(completed, isTrue);
     TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger.setMockMessageHandler('flutter/assets', null);
+
+    testedExtensions.add(ServicesServiceExtensions.evict.name);
   });
 
   test('Service extensions - exit', () async {
     // no test for _calling_ 'exit', because that should terminate the process!
     // Not expecting extension to be available for web platform.
     expect(binding.extensions.containsKey(FoundationServiceExtensions.exit.name), !isBrowser);
+
+    testedExtensions.add(FoundationServiceExtensions.exit.name);
   });
 
   test('Service extensions - platformOverride', () async {
@@ -688,6 +726,8 @@ void main() {
     expect(extensionChangedEvent['extension'], 'ext.flutter.platformOverride');
     expect(extensionChangedEvent['value'], 'android');
     binding.reassembled = 0;
+
+    testedExtensions.add(FoundationServiceExtensions.platformOverride.name);
   });
 
   test('Service extensions - repaintRainbow', () async {
@@ -731,6 +771,8 @@ void main() {
     expect(result, <String, String>{'enabled': 'false'});
     expect(debugRepaintRainbowEnabled, false);
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(RenderingServiceExtensions.repaintRainbow.name);
   });
 
   test('Service extensions - debugDisableClipLayers', () async {
@@ -773,6 +815,8 @@ void main() {
     expect(result, <String, String>{'enabled': 'false'});
     expect(debugDisableClipLayers, false);
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(RenderingServiceExtensions.debugDisableClipLayers.name);
   });
 
   test('Service extensions - debugDisablePhysicalShapeLayers', () async {
@@ -815,6 +859,8 @@ void main() {
     expect(result, <String, String>{'enabled': 'false'});
     expect(debugDisablePhysicalShapeLayers, false);
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(RenderingServiceExtensions.debugDisablePhysicalShapeLayers.name);
   });
 
   test('Service extensions - debugDisableOpacityLayers', () async {
@@ -857,6 +903,8 @@ void main() {
     expect(result, <String, String>{'enabled': 'false'});
     expect(debugDisableOpacityLayers, false);
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(RenderingServiceExtensions.debugDisableOpacityLayers.name);
   });
 
   test('Service extensions - reassemble', () async {
@@ -880,6 +928,8 @@ void main() {
     expect(result, <String, String>{});
     expect(binding.reassembled, 1);
     binding.reassembled = 0;
+
+    testedExtensions.add(FoundationServiceExtensions.reassemble.name);
   });
 
   test('Service extensions - showPerformanceOverlay', () async {
@@ -888,6 +938,7 @@ void main() {
     // The performance overlay service extension is disabled on the web.
     if (kIsWeb) {
       expect(binding.extensions.containsKey(WidgetsServiceExtensions.showPerformanceOverlay.name), isFalse);
+      testedExtensions.add(WidgetsServiceExtensions.showPerformanceOverlay.name);
       return;
     }
 
@@ -909,6 +960,8 @@ void main() {
     expect(result, <String, String>{'enabled': 'false'});
     expect(WidgetsApp.showPerformanceOverlayOverride, false);
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(WidgetsServiceExtensions.showPerformanceOverlay.name);
   });
 
   test('Service extensions - timeDilation', () async {
@@ -945,6 +998,8 @@ void main() {
     expect(timeDilation, 1.0);
     expect(extensionChangedEvents.length, 2);
     expect(binding.frameScheduled, isFalse);
+
+    testedExtensions.add(SchedulerServiceExtensions.timeDilation.name);
   });
 
   test('Service extensions - brightnessOverride', () async {
@@ -953,6 +1008,8 @@ void main() {
     final String brightnessValue = result['value'] as String;
 
     expect(brightnessValue, 'Brightness.light');
+
+    testedExtensions.add(FoundationServiceExtensions.brightnessOverride.name);
   });
 
   test('Service extensions - activeDevToolsServerAddress', () async {
@@ -966,6 +1023,8 @@ void main() {
     result = await binding.testExtension(FoundationServiceExtensions.activeDevToolsServerAddress.name, <String, String>{'value': 'http://127.0.0.1:9102'});
     serverAddress = result['value'] as String;
     expect(serverAddress, 'http://127.0.0.1:9102');
+
+    testedExtensions.add(FoundationServiceExtensions.activeDevToolsServerAddress.name);
   });
 
   test('Service extensions - connectedVmServiceUri', () async {
@@ -979,5 +1038,7 @@ void main() {
     result = await binding.testExtension(FoundationServiceExtensions.connectedVmServiceUri.name, <String, String>{'value': 'http://127.0.0.1:54000/kMUMseKAnog=/'});
     serverAddress = result['value'] as String;
     expect(serverAddress, 'http://127.0.0.1:54000/kMUMseKAnog=/');
+
+    testedExtensions.add(FoundationServiceExtensions.connectedVmServiceUri.name);
   });
 }

packages/flutter/test/widgets/fast_reassemble_test.dart

@@ -1,123 +0,0 @@
-// 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:flutter/foundation.dart';
-import 'package:flutter/widgets.dart';
-import 'package:flutter_test/flutter_test.dart';
-
-void main() {
-  testWidgets('reassemble with a className only marks subtrees from the first matching element as dirty', (WidgetTester tester) async {
-    await tester.pumpWidget(
-      const Foo(Bar(Fizz(SizedBox())))
-    );
-
-    expect(Foo.count, 0);
-    expect(Bar.count, 0);
-    expect(Fizz.count, 0);
-
-    DebugReassembleConfig config = DebugReassembleConfig(widgetName: 'Bar');
-    WidgetsBinding.instance.buildOwner!.reassemble(WidgetsBinding.instance.rootElement!, config);
-
-    expect(Foo.count, 0);
-    expect(Bar.count, 1);
-    expect(Fizz.count, 1);
-
-    config = DebugReassembleConfig(widgetName: 'Fizz');
-    WidgetsBinding.instance.buildOwner!.reassemble(WidgetsBinding.instance.rootElement!, config);
-
-    expect(Foo.count, 0);
-    expect(Bar.count, 1);
-    expect(Fizz.count, 2);
-
-    config = DebugReassembleConfig(widgetName: 'NoMatch');
-    WidgetsBinding.instance.buildOwner!.reassemble(WidgetsBinding.instance.rootElement!, config);
-
-    expect(Foo.count, 0);
-    expect(Bar.count, 1);
-    expect(Fizz.count, 2);
-
-    config = DebugReassembleConfig();
-    WidgetsBinding.instance.buildOwner!.reassemble(WidgetsBinding.instance.rootElement!, config);
-
-    expect(Foo.count, 1);
-    expect(Bar.count, 2);
-    expect(Fizz.count, 3);
-
-    WidgetsBinding.instance.buildOwner!.reassemble(WidgetsBinding.instance.rootElement!, null);
-
-    expect(Foo.count, 2);
-    expect(Bar.count, 3);
-    expect(Fizz.count, 4);
-  });
-}
-
-class Foo extends StatefulWidget {
-  const Foo(this.child, {super.key});
-
-  final Widget child;
-  static int count = 0;
-
-  @override
-  State<Foo> createState() => _FooState();
-}
-
-class _FooState extends State<Foo> {
-  @override
-  void reassemble() {
-    Foo.count += 1;
-    super.reassemble();
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return widget.child;
-  }
-}
-
-
-class Bar extends StatefulWidget {
-  const Bar(this.child, {super.key});
-
-  final Widget child;
-  static int count = 0;
-
-  @override
-  State<Bar> createState() => _BarState();
-}
-
-class _BarState extends State<Bar> {
-  @override
-  void reassemble() {
-    Bar.count += 1;
-    super.reassemble();
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return widget.child;
-  }
-}
-
-class Fizz extends StatefulWidget {
-  const Fizz(this.child, {super.key});
-
-  final Widget child;
-  static int count = 0;
-
-  @override
-  State<Fizz> createState() => _FizzState();
-}
-
-class _FizzState extends State<Fizz> {
-  @override
-  void reassemble() {
-    Fizz.count += 1;
-    super.reassemble();
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return widget.child;
-  }
-}

packages/flutter/test/widgets/widget_inspector_test_utils.dart

@@ -115,7 +115,7 @@ class TestWidgetInspectorService extends Object with WidgetInspectorService {
     final WidgetsBinding binding = WidgetsBinding.instance;
 
     if (binding.rootElement != null) {
-      binding.buildOwner!.reassemble(binding.rootElement!, null);
+      binding.buildOwner!.reassemble(binding.rootElement!);
     }
   }
 

packages/flutter_tools/lib/src/bundle.dart

@@ -33,7 +33,7 @@ String getDefaultCachedKernelPath({
 }) {
   final StringBuffer buffer = StringBuffer();
    final List<String> cacheFrontEndOptions = extraFrontEndOptions.toList()
-     ..removeWhere((String arg) => arg.startsWith('--enable-experiment=') || arg == '--flutter-widget-cache');
+     ..removeWhere((String arg) => arg.startsWith('--enable-experiment='));
   buffer.writeAll(dartDefines);
   buffer.writeAll(cacheFrontEndOptions);
   String buildPrefix = '';

packages/flutter_tools/lib/src/devfs.dart

@@ -401,7 +401,6 @@ class UpdateFSReport {
     bool success = false,
     int invalidatedSourcesCount = 0,
     int syncedBytes = 0,
-    this.fastReassembleClassName,
     int scannedSourcesCount = 0,
     Duration compileDuration = Duration.zero,
     Duration transferDuration = Duration.zero,
@@ -423,7 +422,6 @@ class UpdateFSReport {
   Duration get findInvalidatedDuration => _findInvalidatedDuration;
 
   bool _success;
-  String? fastReassembleClassName;
   int _invalidatedSourcesCount;
   int _syncedBytes;
   int _scannedSourcesCount;
@@ -435,7 +433,6 @@ class UpdateFSReport {
     if (!report._success) {
       _success = false;
     }
-    fastReassembleClassName ??= report.fastReassembleClassName;
     _invalidatedSourcesCount += report._invalidatedSourcesCount;
     _syncedBytes += report._syncedBytes;
     _scannedSourcesCount += report._scannedSourcesCount;
@@ -495,7 +492,6 @@ class DevFS {
   DateTime? lastCompiled;
   DateTime? _previousCompiled;
   PackageConfig? lastPackageConfig;
-  File? _widgetCacheOutputFile;
 
   Uri? _baseUri;
   Uri? get baseUri => _baseUri;
@@ -555,22 +551,6 @@ class DevFS {
     lastCompiled = _previousCompiled;
   }
 
-
-  /// If the build method of a single widget was modified, return the widget name.
-  ///
-  /// If any other changes were made, or there is an error scanning the file,
-  /// return `null`.
-  String? _checkIfSingleWidgetReloadApplied() {
-    final File? widgetCacheOutputFile = _widgetCacheOutputFile;
-    if (widgetCacheOutputFile != null && widgetCacheOutputFile.existsSync()) {
-      final String widget = widgetCacheOutputFile.readAsStringSync().trim();
-      if (widget.isNotEmpty) {
-        return widget;
-      }
-    }
-    return null;
-  }
-
   /// Updates files on the device.
   ///
   /// Returns the number of bytes synced.
@@ -596,7 +576,6 @@ class DevFS {
     final DateTime candidateCompileTime = DateTime.now();
     didUpdateFontManifest = false;
     lastPackageConfig = packageConfig;
-    _widgetCacheOutputFile = _fileSystem.file('$dillOutputPath.incremental.dill.widget_cache');
 
     // Update modified files
     final Map<Uri, DevFSContent> dirtyEntries = <Uri, DevFSContent>{};
@@ -741,7 +720,6 @@ class DevFS {
       success: true,
       syncedBytes: syncedBytes,
       invalidatedSourcesCount: invalidatedFiles.length,
-      fastReassembleClassName: _checkIfSingleWidgetReloadApplied(),
       compileDuration: compileTimer.elapsed,
       transferDuration: transferTimer.elapsed,
     );

packages/flutter_tools/lib/src/features.dart

@@ -44,9 +44,6 @@ abstract class FeatureFlags {
   /// Whether custom devices are enabled.
   bool get areCustomDevicesEnabled => false;
 
-  /// Whether fast single widget reloads are enabled.
-  bool get isSingleWidgetReloadEnabled => false;
-
   /// Whether WebAssembly compilation for Flutter Web is enabled.
   bool get isFlutterWebWasmEnabled => false;
 
@@ -62,7 +59,6 @@ const List<Feature> allFeatures = <Feature>[
   flutterLinuxDesktopFeature,
   flutterMacOSDesktopFeature,
   flutterWindowsDesktopFeature,
-  singleWidgetReload,
   flutterAndroidFeature,
   flutterIOSFeature,
   flutterFuchsiaFeature,
@@ -140,20 +136,6 @@ const Feature flutterCustomDevicesFeature = Feature(
   ),
 );
 
-/// The fast hot reload feature for https://github.com/flutter/flutter/issues/61407.
-const Feature singleWidgetReload = Feature(
-  name: 'Hot reload optimization for changes to class body of a single widget',
-  configSetting: 'single-widget-reload-optimization',
-  environmentOverride: 'FLUTTER_SINGLE_WIDGET_RELOAD',
-  master: FeatureChannelSetting(
-    available: true,
-    enabledByDefault: true,
-  ),
-  beta: FeatureChannelSetting(
-    available: true,
-  ),
-);
-
 /// Enabling WebAssembly compilation from `flutter build web`
 const Feature flutterWebWasm = Feature(
   name: 'WebAssembly compilation from flutter build web',

packages/flutter_tools/lib/src/flutter_features.dart

@@ -44,9 +44,6 @@ class FlutterFeatureFlags implements FeatureFlags {
   @override
   bool get areCustomDevicesEnabled => isEnabled(flutterCustomDevicesFeature);
 
-  @override
-  bool get isSingleWidgetReloadEnabled => isEnabled(singleWidgetReload);
-
   @override
   bool get isFlutterWebWasmEnabled => isEnabled(flutterWebWasm);
 

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

@@ -446,7 +446,6 @@ Please provide a valid TCP port (an integer between 0 and 65535, inclusive).
         fullRestart: true,
         reason: reason,
         overallTimeInMs: elapsed.inMilliseconds,
-        fastReassemble: false,
       ).send();
     }
     return OperationResult.ok;

packages/flutter_tools/lib/src/reporting/custom_dimensions.dart

@@ -58,7 +58,6 @@ class CustomDimensions {
     this.commandRunAndroidEmbeddingVersion,
     this.commandPackagesAndroidEmbeddingVersion,
     this.nullSafety,
-    this.fastReassemble,
     this.nullSafeMigratedLibraries,
     this.nullSafeTotalLibraries,
     this.hotEventCompileTimeInMs,
@@ -118,7 +117,7 @@ class CustomDimensions {
   final String? commandRunAndroidEmbeddingVersion;  // cd45
   final String? commandPackagesAndroidEmbeddingVersion;  // cd46
   final bool? nullSafety;  // cd47
-  final bool? fastReassemble;  // cd48
+  // cd48 was fastReassemble but that feature was removed
   final int? nullSafeMigratedLibraries;  // cd49
   final int? nullSafeTotalLibraries;  // cd50
   final int? hotEventCompileTimeInMs;  // cd51
@@ -179,7 +178,6 @@ class CustomDimensions {
       if (commandRunAndroidEmbeddingVersion != null) CustomDimensionsEnum.commandRunAndroidEmbeddingVersion.cdKey: commandRunAndroidEmbeddingVersion.toString(),
       if (commandPackagesAndroidEmbeddingVersion != null) CustomDimensionsEnum.commandPackagesAndroidEmbeddingVersion.cdKey: commandPackagesAndroidEmbeddingVersion.toString(),
       if (nullSafety != null) CustomDimensionsEnum.nullSafety.cdKey: nullSafety.toString(),
-      if (fastReassemble != null) CustomDimensionsEnum.fastReassemble.cdKey: fastReassemble.toString(),
       if (nullSafeMigratedLibraries != null) CustomDimensionsEnum.nullSafeMigratedLibraries.cdKey: nullSafeMigratedLibraries.toString(),
       if (nullSafeTotalLibraries != null) CustomDimensionsEnum.nullSafeTotalLibraries.cdKey: nullSafeTotalLibraries.toString(),
       if (hotEventCompileTimeInMs != null) CustomDimensionsEnum.hotEventCompileTimeInMs.cdKey: hotEventCompileTimeInMs.toString(),
@@ -247,7 +245,6 @@ class CustomDimensions {
       commandRunAndroidEmbeddingVersion: other.commandRunAndroidEmbeddingVersion ?? commandRunAndroidEmbeddingVersion,
       commandPackagesAndroidEmbeddingVersion: other.commandPackagesAndroidEmbeddingVersion ?? commandPackagesAndroidEmbeddingVersion,
       nullSafety: other.nullSafety ?? nullSafety,
-      fastReassemble: other.fastReassemble ?? fastReassemble,
       nullSafeMigratedLibraries: other.nullSafeMigratedLibraries ?? nullSafeMigratedLibraries,
       nullSafeTotalLibraries: other.nullSafeTotalLibraries ?? nullSafeTotalLibraries,
       hotEventCompileTimeInMs: other.hotEventCompileTimeInMs ?? hotEventCompileTimeInMs,
@@ -309,7 +306,6 @@ class CustomDimensions {
       commandRunAndroidEmbeddingVersion: _extractString(map, CustomDimensionsEnum.commandRunAndroidEmbeddingVersion),
       commandPackagesAndroidEmbeddingVersion: _extractString(map, CustomDimensionsEnum.commandPackagesAndroidEmbeddingVersion),
       nullSafety: _extractBool(map, CustomDimensionsEnum.nullSafety),
-      fastReassemble: _extractBool(map, CustomDimensionsEnum.fastReassemble),
       nullSafeMigratedLibraries: _extractInt(map, CustomDimensionsEnum.nullSafeMigratedLibraries),
       nullSafeTotalLibraries: _extractInt(map, CustomDimensionsEnum.nullSafeTotalLibraries),
       hotEventCompileTimeInMs: _extractInt(map, CustomDimensionsEnum.hotEventCompileTimeInMs),
@@ -397,7 +393,7 @@ enum CustomDimensionsEnum {
   commandRunAndroidEmbeddingVersion,  // cd45
   commandPackagesAndroidEmbeddingVersion,  // cd46
   nullSafety,  // cd47
-  fastReassemble,  // cd48
+  obsolete1,  // cd48 (was fastReassemble)
   nullSafeMigratedLibraries,  // cd49
   nullSafeTotalLibraries,  // cd50
   hotEventCompileTimeInMs,  // cd51

packages/flutter_tools/lib/src/reporting/events.dart

@@ -39,7 +39,6 @@ class HotEvent extends UsageEvent {
     required this.sdkName,
     required this.emulator,
     required this.fullRestart,
-    required this.fastReassemble,
     this.reason,
     this.finalLibraryCount,
     this.syncedLibraryCount,
@@ -63,7 +62,6 @@ class HotEvent extends UsageEvent {
   final String sdkName;
   final bool emulator;
   final bool fullRestart;
-  final bool fastReassemble;
   final int? finalLibraryCount;
   final int? syncedLibraryCount;
   final int? syncedClassesCount;
@@ -94,7 +92,6 @@ class HotEvent extends UsageEvent {
       hotEventInvalidatedSourcesCount: invalidatedSourcesCount,
       hotEventTransferTimeInMs: transferTimeInMs,
       hotEventOverallTimeInMs: overallTimeInMs,
-      fastReassemble: fastReassemble,
       hotEventCompileTimeInMs: compileTimeInMs,
       hotEventFindInvalidatedTimeInMs: findInvalidatedTimeInMs,
       hotEventScannedSourcesCount: scannedSourcesCount,

packages/flutter_tools/lib/src/resident_runner.dart

@@ -34,7 +34,6 @@ import 'compile.dart';
 import 'convert.dart';
 import 'devfs.dart';
 import 'device.dart';
-import 'features.dart';
 import 'globals.dart' as globals;
 import 'ios/application_package.dart';
 import 'ios/devices.dart';
@@ -169,11 +168,8 @@ class FlutterDevice {
         platform: platform,
       );
     } else {
-      // The flutter-widget-cache feature only applies to run mode.
       List<String> extraFrontEndOptions = buildInfo.extraFrontEndOptions;
       extraFrontEndOptions = <String>[
-        if (featureFlags.isSingleWidgetReloadEnabled)
-         '--flutter-widget-cache',
         '--enable-experiment=alternative-invalidation-strategy',
         ...extraFrontEndOptions,
       ];

packages/flutter_tools/lib/src/run_hot.dart

@@ -20,7 +20,6 @@ import 'convert.dart';
 import 'dart/package_map.dart';
 import 'devfs.dart';
 import 'device.dart';
-import 'features.dart';
 import 'globals.dart' as globals;
 import 'project.dart';
 import 'reporting/reporting.dart';
@@ -415,7 +414,6 @@ class HotRunner extends ResidentRunner {
       sdkName: _sdkName!,
       emulator: _emulator!,
       fullRestart: false,
-      fastReassemble: false,
       overallTimeInMs: appStartedTimer.elapsed.inMilliseconds,
       compileTimeInMs: totalCompileTime.inMilliseconds,
       transferTimeInMs: totalLaunchAppTime.inMilliseconds,
@@ -802,7 +800,6 @@ class HotRunner extends ResidentRunner {
           emulator: emulator!,
           fullRestart: true,
           reason: reason,
-          fastReassemble: false,
           overallTimeInMs: restartTimer.elapsed.inMilliseconds,
           syncedBytes: result.updateFSReport?.syncedBytes,
           invalidatedSourcesCount: result.updateFSReport?.invalidatedSourcesCount,
@@ -828,7 +825,6 @@ class HotRunner extends ResidentRunner {
           emulator: emulator!,
           fullRestart: true,
           reason: reason,
-          fastReassemble: false,
         ).send();
       }
       status?.cancel();
@@ -878,7 +874,6 @@ class HotRunner extends ResidentRunner {
           emulator: emulator!,
           fullRestart: false,
           reason: reason,
-          fastReassemble: false,
         ).send();
       } else {
         HotEvent('exception',
@@ -887,7 +882,6 @@ class HotRunner extends ResidentRunner {
           emulator: emulator!,
           fullRestart: false,
           reason: reason,
-          fastReassemble: false,
         ).send();
       }
       return OperationResult(errorCode, errorMessage, fatal: true);
@@ -971,7 +965,6 @@ class HotRunner extends ResidentRunner {
       viewCache,
       onSlow,
       reloadMessage,
-      updatedDevFS.fastReassembleClassName,
     );
     shouldReportReloadTime = reassembleResult.shouldReportReloadTime;
     if (reassembleResult.reassembleViews.isEmpty) {
@@ -1005,7 +998,6 @@ class HotRunner extends ResidentRunner {
       syncedBytes: updatedDevFS.syncedBytes,
       invalidatedSourcesCount: updatedDevFS.invalidatedSourcesCount,
       transferTimeInMs: updatedDevFS.transferDuration.inMilliseconds,
-      fastReassemble: featureFlags.isSingleWidgetReloadEnabled && updatedDevFS.fastReassembleClassName != null,
       compileTimeInMs: updatedDevFS.compileDuration.inMilliseconds,
       findInvalidatedTimeInMs: updatedDevFS.findInvalidatedDuration.inMilliseconds,
       scannedSourcesCount: updatedDevFS.scannedSourcesCount,
@@ -1225,7 +1217,6 @@ Future<OperationResult> defaultReloadSourcesHelper(
       emulator: emulator!,
       fullRestart: false,
       reason: reason,
-      fastReassemble: false,
       usage: usage,
     ).send();
     // Reset devFS lastCompileTime to ensure the file will still be marked
@@ -1288,7 +1279,6 @@ typedef ReassembleHelper = Future<ReassembleResult> Function(
   Map<FlutterDevice?, List<FlutterView>> viewCache,
   void Function(String message)? onSlow,
   String reloadMessage,
-  String? fastReassembleClassName,
 );
 
 Future<ReassembleResult> _defaultReassembleHelper(
@@ -1296,7 +1286,6 @@ Future<ReassembleResult> _defaultReassembleHelper(
   Map<FlutterDevice?, List<FlutterView>> viewCache,
   void Function(String message)? onSlow,
   String reloadMessage,
-  String? fastReassembleClassName,
 ) async {
   // Check if any isolates are paused and reassemble those that aren't.
   final Map<FlutterView, FlutterVmService?> reassembleViews = <FlutterView, FlutterVmService?>{};
@@ -1325,17 +1314,9 @@ Future<ReassembleResult> _defaultReassembleHelper(
         reassembleViews[view] = device.vmService;
         // If the tool identified a change in a single widget, do a fast instead
         // of a full reassemble.
-        Future<void> reassembleWork;
+        final Future<void> reassembleWork = device.vmService!.flutterReassemble(
-        if (fastReassembleClassName != null) {
-          reassembleWork = device.vmService!.flutterFastReassemble(
-            isolateId: view.uiIsolate!.id!,
-            className: fastReassembleClassName,
-          );
-        } else {
-          reassembleWork = device.vmService!.flutterReassemble(
           isolateId: view.uiIsolate!.id!,
         );
-        }
         reassembleFutures.add(reassembleWork.then(
           (Object? obj) => obj,
           onError: (Object error, StackTrace stackTrace) {

packages/flutter_tools/lib/src/vmservice.dart

@@ -809,19 +809,6 @@ class FlutterVmService {
     );
   }
 
-  Future<Map<String, Object?>?> flutterFastReassemble({
-   required String isolateId,
-   required String className,
-  }) {
-    return invokeFlutterExtensionRpcRaw(
-      'ext.flutter.fastReassemble',
-      isolateId: isolateId,
-      args: <String, Object>{
-        'className': className,
-      },
-    );
-  }
-
   Future<bool> flutterAlreadyPaintedFirstUsefulFrame({
     required String isolateId,
   }) async {

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

@@ -118,14 +118,14 @@ void main() {
     ProcessManager: () => FakeProcessManager.any(),
   });
 
-  testWithoutContext('--flutter-widget-cache and --enable-experiment are removed from getDefaultCachedKernelPath hash', () {
+  testWithoutContext('--enable-experiment is removed from getDefaultCachedKernelPath hash', () {
     final FileSystem fileSystem = MemoryFileSystem.test();
     final Config config = Config.test();
 
     expect(getDefaultCachedKernelPath(
       trackWidgetCreation: true,
       dartDefines: <String>[],
-      extraFrontEndOptions: <String>['--enable-experiment=foo', '--flutter-widget-cache'],
+      extraFrontEndOptions: <String>['--enable-experiment=foo'],
       fileSystem: fileSystem,
       config: config,
     ), 'build/cache.dill.track.dill');
@@ -133,7 +133,7 @@ void main() {
     expect(getDefaultCachedKernelPath(
       trackWidgetCreation: true,
       dartDefines: <String>['foo=bar'],
-      extraFrontEndOptions: <String>['--enable-experiment=foo', '--flutter-widget-cache'],
+      extraFrontEndOptions: <String>['--enable-experiment=foo'],
       fileSystem: fileSystem,
       config: config,
     ), 'build/06ad47d8e64bd28de537b62ff85357c4.cache.dill.track.dill');
@@ -141,7 +141,7 @@ void main() {
     expect(getDefaultCachedKernelPath(
       trackWidgetCreation: false,
       dartDefines: <String>[],
-      extraFrontEndOptions: <String>['--enable-experiment=foo', '--flutter-widget-cache'],
+      extraFrontEndOptions: <String>['--enable-experiment=foo'],
       fileSystem: fileSystem,
       config: config,
     ), 'build/cache.dill');
@@ -149,7 +149,7 @@ void main() {
     expect(getDefaultCachedKernelPath(
       trackWidgetCreation: true,
       dartDefines: <String>[],
-      extraFrontEndOptions: <String>['--enable-experiment=foo', '--flutter-widget-cache', '--foo=bar'],
+      extraFrontEndOptions: <String>['--enable-experiment=foo', '--foo=bar'],
       fileSystem: fileSystem,
       config: config,
     ), 'build/95b595cca01caa5f0ca0a690339dd7f6.cache.dill.track.dill');

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

@@ -178,7 +178,6 @@ void main() {
             Map<FlutterDevice?, List<FlutterView>> viewCache,
             void Function(String message)? onSlow,
             String reloadMessage,
-            String? fastReassembleClassName,
           ) async => ReassembleResult(
               <FlutterView?, FlutterVmService?>{null: null},
               false,
@@ -296,7 +295,6 @@ void main() {
             hotEventSdkName: 'Tester',
             hotEventEmulator: false,
             hotEventFullRestart: true,
-            fastReassemble: false,
             hotEventOverallTimeInMs: 64000,
             hotEventSyncedBytes: 4,
             hotEventInvalidatedSourcesCount: 2,
@@ -379,7 +377,6 @@ void main() {
             Map<FlutterDevice?, List<FlutterView>> viewCache,
             void Function(String message)? onSlow,
             String reloadMessage,
-            String? fastReassembleClassName,
           ) async => ReassembleResult(
               <FlutterView?, FlutterVmService?>{null: null},
               false,
@@ -402,7 +399,6 @@ void main() {
             hotEventSdkName: 'Tester',
             hotEventEmulator: false,
             hotEventFullRestart: false,
-            fastReassemble: false,
             hotEventCompileTimeInMs: 16000,
             hotEventFindInvalidatedTimeInMs: 64000,
             hotEventScannedSourcesCount: 16,

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

@@ -25,7 +25,6 @@ import 'package:flutter_tools/src/convert.dart';
 import 'package:flutter_tools/src/devfs.dart';
 import 'package:flutter_tools/src/device.dart';
 import 'package:flutter_tools/src/device_port_forwarder.dart';
-import 'package:flutter_tools/src/features.dart';
 import 'package:flutter_tools/src/globals.dart' as globals;
 import 'package:flutter_tools/src/project.dart';
 import 'package:flutter_tools/src/reporting/reporting.dart';
@@ -424,7 +423,6 @@ void main() {
         hotEventSdkName: 'Android',
         hotEventEmulator: false,
         hotEventFullRestart: false,
-        fastReassemble: false,
       )),
     ));
     expect(fakeVmServiceHost?.hasRemainingExpectations, false);
@@ -480,7 +478,6 @@ void main() {
         hotEventSdkName: 'Android',
         hotEventEmulator: false,
         hotEventFullRestart: false,
-        fastReassemble: false,
       )),
     ));
     expect(fakeVmServiceHost?.hasRemainingExpectations, false);
@@ -527,7 +524,6 @@ void main() {
         hotEventSdkName: 'Android',
         hotEventEmulator: false,
         hotEventFullRestart: false,
-        fastReassemble: false,
       )),
     ));
     expect(fakeVmServiceHost?.hasRemainingExpectations, false);
@@ -766,96 +762,6 @@ void main() {
     Usage: () => TestUsage(),
   }));
 
-  testUsingContext('ResidentRunner can perform fast reassemble', () => testbed.run(() async {
-    fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[
-      listViews,
-      FakeVmServiceRequest(
-        method: 'getVM',
-        jsonResponse: fakeVM.toJson(),
-      ),
-      listViews,
-      listViews,
-      FakeVmServiceRequest(
-        method: 'getVM',
-        jsonResponse: fakeVM.toJson(),
-      ),
-      const FakeVmServiceRequest(
-        method: kReloadSourcesServiceName,
-        args: <String, Object>{
-          'isolateId': '1',
-          'pause': false,
-          'rootLibUri': 'main.dart.incremental.dill',
-        },
-        jsonResponse: <String, Object>{
-          'type': 'ReloadReport',
-          'success': true,
-          'details': <String, Object>{
-            'loadedLibraryCount': 1,
-          },
-        },
-      ),
-      FakeVmServiceRequest(
-        method: 'getIsolatePauseEvent',
-        args: <String, Object>{
-          'isolateId': '1',
-        },
-        jsonResponse: fakeUnpausedEvent.toJson(),
-      ),
-      FakeVmServiceRequest(
-        method: 'ext.flutter.fastReassemble',
-        args: <String, Object?>{
-          'isolateId': fakeUnpausedIsolate.id,
-          'className': 'FOO',
-        },
-      ),
-    ]);
-    final FakeDelegateFlutterDevice flutterDevice = FakeDelegateFlutterDevice(
-      device,
-      BuildInfo.debug,
-      FakeResidentCompiler(),
-      devFS,
-    )..vmService = fakeVmServiceHost!.vmService;
-    residentRunner = HotRunner(
-      <FlutterDevice>[
-        flutterDevice,
-      ],
-      stayResident: false,
-      debuggingOptions: DebuggingOptions.enabled(BuildInfo.debug),
-      target: 'main.dart',
-      devtoolsHandler: createNoOpHandler,
-    );
-    devFS.nextUpdateReport = UpdateFSReport(
-      success: true,
-      fastReassembleClassName: 'FOO',
-      invalidatedSourcesCount: 1,
-    );
-
-    final Completer<DebugConnectionInfo> futureConnectionInfo = Completer<DebugConnectionInfo>.sync();
-    final Completer<void> futureAppStart = Completer<void>.sync();
-    unawaited(residentRunner.attach(
-      appStartedCompleter: futureAppStart,
-      connectionInfoCompleter: futureConnectionInfo,
-      enableDevTools: true,
-    ));
-
-    await futureAppStart.future;
-    final OperationResult result = await residentRunner.restart();
-
-    expect(result.fatal, false);
-    expect(result.code, 0);
-
-    final TestUsageEvent event = (globals.flutterUsage as TestUsage).events.first;
-    expect(event.category, 'hot');
-    expect(event.parameter, 'reload');
-    expect(event.parameters?.fastReassemble, true);
-  }, overrides: <Type, Generator>{
-    FileSystem: () => MemoryFileSystem.test(),
-    Platform: () => FakePlatform(),
-    ProjectFileInvalidator: () => FakeProjectFileInvalidator(),
-    Usage: () => TestUsage(),
-    FeatureFlags: () => TestFeatureFlags(isSingleWidgetReloadEnabled: true),
-  }));
-
   testUsingContext('ResidentRunner reports hot reload time details', () => testbed.run(() async {
     fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[
       listViews,
@@ -893,10 +799,9 @@ void main() {
         jsonResponse: fakeUnpausedEvent.toJson(),
       ),
       FakeVmServiceRequest(
-        method: 'ext.flutter.fastReassemble',
+        method: 'ext.flutter.reassemble',
         args: <String, Object?>{
           'isolateId': fakeUnpausedIsolate.id,
-          'className': 'FOO',
         },
       ),
     ]);
@@ -917,7 +822,6 @@ void main() {
     );
     devFS.nextUpdateReport = UpdateFSReport(
       success: true,
-      fastReassembleClassName: 'FOO',
       invalidatedSourcesCount: 1,
     );
 
@@ -942,7 +846,6 @@ void main() {
     Platform: () => FakePlatform(),
     ProjectFileInvalidator: () => FakeProjectFileInvalidator(),
     Usage: () => TestUsage(),
-    FeatureFlags: () => TestFeatureFlags(isSingleWidgetReloadEnabled: true),
   }));
 
   testUsingContext('ResidentRunner can send target platform to analytics from full restart', () => testbed.run(() async {
@@ -1225,7 +1128,6 @@ void main() {
         hotEventSdkName: 'Android',
         hotEventEmulator: false,
         hotEventFullRestart: true,
-        fastReassemble: false,
       )),
     ));
     expect(fakeVmServiceHost?.hasRemainingExpectations, false);
@@ -1984,30 +1886,6 @@ flutter:
     ProcessManager: () => FakeProcessManager.any(),
   });
 
-  testUsingContext('FlutterDevice passes flutter-widget-cache flag when feature is enabled', () async {
-    fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[]);
-    final FakeDevice device = FakeDevice();
-
-    final DefaultResidentCompiler? residentCompiler = (await FlutterDevice.create(
-      device,
-      buildInfo: const BuildInfo(
-        BuildMode.debug,
-        '',
-        treeShakeIcons: false,
-        extraFrontEndOptions: <String>[],
-      ),
-      target: null, platform: FakePlatform(),
-    )).generator as DefaultResidentCompiler?;
-
-    expect(residentCompiler!.extraFrontEndOptions,
-      contains('--flutter-widget-cache'));
-  }, overrides: <Type, Generator>{
-    Artifacts: () => Artifacts.test(),
-    FileSystem: () => MemoryFileSystem.test(),
-    ProcessManager: () => FakeProcessManager.any(),
-    FeatureFlags: () => TestFeatureFlags(isSingleWidgetReloadEnabled: true),
-  });
-
   testUsingContext('FlutterDevice passes alternative-invalidation-strategy flag', () async {
     fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[]);
     final FakeDevice device = FakeDevice();

packages/flutter_tools/test/integration.shard/single_widget_reload_test.dart

@@ -1,63 +0,0 @@
-// 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 'dart:async';
-
-import 'package:flutter_tools/src/base/file_system.dart';
-
-import '../src/common.dart';
-import 'test_data/single_widget_reload_project.dart';
-import 'test_driver.dart';
-import 'test_utils.dart';
-
-void main() {
-  late Directory tempDir;
-  final SingleWidgetReloadProject project = SingleWidgetReloadProject();
-  late FlutterRunTestDriver flutter;
-
-  setUp(() async {
-    tempDir = createResolvedTempDirectorySync('hot_reload_test.');
-    await project.setUpIn(tempDir);
-    flutter = FlutterRunTestDriver(tempDir);
-  });
-
-  tearDown(() async {
-    await flutter.stop();
-    tryToDelete(tempDir);
-  });
-
-  testWithoutContext('newly added code executes during hot reload with single widget reloads, but only invalidated widget', () async {
-    final StringBuffer stdout = StringBuffer();
-    final StreamSubscription<String> subscription = flutter.stdout.listen(stdout.writeln);
-    await flutter.run(singleWidgetReloads: true);
-    project.uncommentHotReloadPrint();
-    try {
-      await flutter.hotReload();
-      expect(stdout.toString(), allOf(
-        contains('(((TICK 1)))'),
-        contains('(((((RELOAD WORKED)))))'),
-        // Does not invalidate parent widget, so second tick is not output.
-        isNot(contains('(((TICK 2)))'),
-      )));
-    } finally {
-      await subscription.cancel();
-    }
-  });
-
-  testWithoutContext('changes outside of the class body triggers a full reload', () async {
-    final StringBuffer stdout = StringBuffer();
-    final StreamSubscription<String> subscription = flutter.stdout.listen(stdout.writeln);
-    await flutter.run(singleWidgetReloads: true);
-    project.modifyFunction();
-    try {
-      await flutter.hotReload();
-      expect(stdout.toString(), allOf(
-        contains('(((TICK 1)))'),
-        contains('(((TICK 2)))'),
-      ));
-    } finally {
-      await subscription.cancel();
-    }
-  });
-}

packages/flutter_tools/test/integration.shard/test_data/single_widget_reload_project.dart

@@ -1,94 +0,0 @@
-// 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 '../test_utils.dart';
-import 'project.dart';
-
-class SingleWidgetReloadProject extends Project {
-  @override
-  final String pubspec = '''
-  name: test
-  environment:
-    sdk: '>=3.0.0-0 <4.0.0'
-
-  dependencies:
-    flutter:
-      sdk: flutter
-  ''';
-
-  @override
-  final String main = r'''
-  import 'package:flutter/material.dart';
-  import 'package:flutter/scheduler.dart';
-  import 'package:flutter/services.dart';
-  import 'package:flutter/widgets.dart';
-
-  void main() async {
-    WidgetsFlutterBinding.ensureInitialized();
-    final ByteData message = const StringCodec().encodeMessage('AppLifecycleState.resumed')!;
-    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', message, (_) { });
-    runApp(MyApp());
-  }
-
-  int count = 1;
-
-  class MyApp extends StatelessWidget {
-    @override
-    Widget build(BuildContext context) {
-      // PARENT WIDGET
-
-      print('((((TICK $count))))');
-      count += 1;
-
-      return MaterialApp(
-        title: 'Flutter Demo',
-        home: SecondWidget(),
-      );
-    }
-  }
-
-  class SecondWidget extends StatelessWidget {
-    @override
-    Widget build(BuildContext context) {
-      // Do not remove the next line, it's uncommented by a test to verify that
-      // hot reloading worked:
-      // printHotReloadWorked();
-      return Container();
-    }
-  }
-
-  void printHotReloadWorked() {
-    // The call to this function is uncommented by a test to verify that hot
-    // reloading worked.
-    print('(((((RELOAD WORKED)))))');
-  }
-  ''';
-
-  Uri get parentWidgetUri => mainDart;
-  int get parentWidgetLine => lineContaining(main, '// PARENT WIDGET');
-
-  void uncommentHotReloadPrint() {
-    final String newMainContents = main.replaceAll(
-      '// printHotReloadWorked();',
-      'printHotReloadWorked();',
-    );
-    writeFile(
-      fileSystem.path.join(dir.path, 'lib', 'main.dart'),
-      newMainContents,
-      writeFutureModifiedDate: true,
-    );
-  }
-
-  void modifyFunction() {
-    final String newMainContents = main.replaceAll(
-      '(((((RELOAD WORKED)))))',
-      '(((((RELOAD WORKED 2)))))',
-    );
-    writeFile(
-      fileSystem.path.join(dir.path, 'lib', 'main.dart'),
-      newMainContents,
-      writeFutureModifiedDate: true,
-    );
-  }
-}

packages/flutter_tools/test/integration.shard/test_driver.dart

@@ -90,7 +90,6 @@ abstract class FlutterTestDriver {
     List<String> arguments, {
     String? script,
     bool withDebugger = false,
-    bool singleWidgetReloads = false,
   }) async {
     final String flutterBin = fileSystem.path.join(getFlutterRoot(), 'bin', 'flutter');
     if (withDebugger) {
@@ -114,8 +113,6 @@ abstract class FlutterTestDriver {
       environment: <String, String>{
         'FLUTTER_TEST': 'true',
         'FLUTTER_WEB': 'true',
-        if (singleWidgetReloads)
-          'FLUTTER_SINGLE_WIDGET_RELOAD': 'true',
       },
     );
 
@@ -511,7 +508,6 @@ class FlutterRunTestDriver extends FlutterTestDriver {
     bool chrome = false,
     bool expressionEvaluation = true,
     bool structuredErrors = false,
-    bool singleWidgetReloads = false,
     bool serveObservatory = false,
     String? script,
     List<String>? additionalCommandArgs,
@@ -542,7 +538,6 @@ class FlutterRunTestDriver extends FlutterTestDriver {
       startPaused: startPaused,
       pauseOnExceptions: pauseOnExceptions,
       script: script,
-      singleWidgetReloads: singleWidgetReloads,
     );
   }
 
@@ -551,7 +546,6 @@ class FlutterRunTestDriver extends FlutterTestDriver {
     bool withDebugger = false,
     bool startPaused = false,
     bool pauseOnExceptions = false,
-    bool singleWidgetReloads = false,
     bool serveObservatory = false,
     List<String>? additionalCommandArgs,
   }) async {
@@ -573,7 +567,6 @@ class FlutterRunTestDriver extends FlutterTestDriver {
       withDebugger: withDebugger,
       startPaused: startPaused,
       pauseOnExceptions: pauseOnExceptions,
-      singleWidgetReloads: singleWidgetReloads,
       attachPort: port,
     );
   }
@@ -585,7 +578,6 @@ class FlutterRunTestDriver extends FlutterTestDriver {
     bool withDebugger = false,
     bool startPaused = false,
     bool pauseOnExceptions = false,
-    bool singleWidgetReloads = false,
     int? attachPort,
   }) async {
     assert(!startPaused || withDebugger);
@@ -593,7 +585,6 @@ class FlutterRunTestDriver extends FlutterTestDriver {
       args,
       script: script,
       withDebugger: withDebugger,
-      singleWidgetReloads: singleWidgetReloads,
     );
 
     final Completer<void> prematureExitGuard = Completer<void>();
@@ -806,13 +797,11 @@ class FlutterTestTestDriver extends FlutterTestDriver {
     bool withDebugger = false,
     bool pauseOnExceptions = false,
     Future<void> Function()? beforeStart,
-    bool singleWidgetReloads = false,
   }) async {
     await super._setupProcess(
       args,
       script: script,
       withDebugger: withDebugger,
-      singleWidgetReloads: singleWidgetReloads,
     );
 
     // Stash the PID so that we can terminate the VM more reliably than using

packages/flutter_tools/test/src/fakes.dart

@@ -443,7 +443,6 @@ class TestFeatureFlags implements FeatureFlags {
     this.isMacOSEnabled = false,
     this.isWebEnabled = false,
     this.isWindowsEnabled = false,
-    this.isSingleWidgetReloadEnabled = false,
     this.isAndroidEnabled = true,
     this.isIOSEnabled = true,
     this.isFuchsiaEnabled = false,
@@ -463,9 +462,6 @@ class TestFeatureFlags implements FeatureFlags {
   @override
   final bool isWindowsEnabled;
 
-  @override
-  final bool isSingleWidgetReloadEnabled;
-
   @override
   final bool isAndroidEnabled;
 
@@ -492,8 +488,6 @@ class TestFeatureFlags implements FeatureFlags {
         return isMacOSEnabled;
       case flutterWindowsDesktopFeature:
         return isWindowsEnabled;
-      case singleWidgetReload:
-        return isSingleWidgetReloadEnabled;
       case flutterAndroidFeature:
         return isAndroidEnabled;
       case flutterIOSFeature: