Send ServiceExtensionToggled event when service extension is set to a value. (#26426)

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

@@ -129,8 +129,9 @@ abstract class BindingBase {
     }
 
     assert(() {
+      const String platformOverrideExtensionName = 'platformOverride';
       registerServiceExtension(
-        name: 'platformOverride',
+        name: platformOverrideExtensionName,
         callback: (Map<String, String> parameters) async {
           if (parameters.containsKey('value')) {
             switch (parameters['value']) {
@@ -147,6 +148,10 @@ abstract class BindingBase {
               default:
                 debugDefaultTargetPlatformOverride = null;
             }
+            _postExtensionStateChangedEvent(
+              platformOverrideExtensionName,
+              defaultTargetPlatform.toString().substring('$TargetPlatform.'.length),
+            );
             await reassembleApplication();
           }
           return <String, dynamic>{
@@ -295,8 +300,10 @@ abstract class BindingBase {
     registerServiceExtension(
       name: name,
       callback: (Map<String, String> parameters) async {
-        if (parameters.containsKey('enabled'))
+        if (parameters.containsKey('enabled')) {
           await setter(parameters['enabled'] == 'true');
+          _postExtensionStateChangedEvent(name, await getter() ? 'true' : 'false');
+        }
         return <String, dynamic>{ 'enabled': await getter() ? 'true' : 'false' };
       }
     );
@@ -327,13 +334,44 @@ abstract class BindingBase {
     registerServiceExtension(
       name: name,
       callback: (Map<String, String> parameters) async {
-        if (parameters.containsKey(name))
+        if (parameters.containsKey(name)) {
           await setter(double.parse(parameters[name]));
+          _postExtensionStateChangedEvent(name, (await getter()).toString());
+        }
         return <String, dynamic>{ name: (await getter()).toString() };
       }
     );
   }
 
+  /// Sends an event when a service extension's state is changed.
+  ///
+  /// Clients should listen for this event to stay aware of the current service
+  /// extension state. Any service extension that manages a state should call
+  /// this method on state change.
+  ///
+  /// `value` reflects the newly updated service extension value.
+  ///
+  /// This will be called automatically for service extensions registered via
+  /// [registerBoolServiceExtension], [registerNumericServiceExtension], or
+  /// [registerStringServiceExtension].
+  void _postExtensionStateChangedEvent(String name, dynamic value) {
+    postEvent(
+      'Flutter.ServiceExtensionStateChanged',
+      <String, dynamic>{
+        'extension': 'ext.flutter.$name',
+        'value': value,
+      },
+    );
+  }
+
+  /// All events dispatched by a [BindingBase] use this method instead of
+  /// calling [developer.postEvent] directly so that tests for [BindingBase]
+  /// can track which events were dispatched by overriding this method.
+  @protected
+  void postEvent(String eventKind, Map<String, dynamic> eventData) {
+    developer.postEvent(eventKind, eventData);
+  }
+
   /// Registers a service extension method with the given name (full name
   /// "ext.flutter.name"), which optionally takes a single argument with the
   /// name "value". If the argument is omitted, the value is to be read,
@@ -358,8 +396,10 @@ abstract class BindingBase {
     registerServiceExtension(
       name: name,
       callback: (Map<String, String> parameters) async {
-        if (parameters.containsKey('value'))
+        if (parameters.containsKey('value')) {
           await setter(parameters['value']);
+          _postExtensionStateChangedEvent(name, await getter());
+        }
         return <String, dynamic>{ 'value': await getter() };
       }
     );

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

@@ -868,13 +868,36 @@ mixin WidgetInspectorService {
     registerServiceExtension(
       name: name,
       callback: (Map<String, String> parameters) async {
-        if (parameters.containsKey('enabled'))
-          await setter(parameters['enabled'] == 'true');
+        if (parameters.containsKey('enabled')) {
+          final bool value = parameters['enabled'] == 'true';
+          await setter(value);
+          _postExtensionStateChangedEvent(name, value);
+        }
         return <String, dynamic>{ 'enabled': await getter() ? 'true' : 'false' };
       },
     );
   }
 
+  /// Sends an event when a service extension's state is changed.
+  ///
+  /// Clients should listen for this event to stay aware of the current service
+  /// extension state. Any service extension that manages a state should call
+  /// this method on state change.
+  ///
+  /// `value` reflects the newly updated service extension value.
+  ///
+  /// This will be called automatically for service extensions registered via
+  /// [registerBoolServiceExtension].
+  void _postExtensionStateChangedEvent(String name, dynamic value) {
+    postEvent(
+      'Flutter.ServiceExtensionStateChanged',
+      <String, dynamic>{
+        'extension': 'ext.flutter.inspector.$name',
+        'value': value,
+      },
+    );
+  }
+
   /// Registers a service extension method with the given name (full
   /// name "ext.flutter.inspector.name") which takes an optional parameter named
   /// "arg" and a required parameter named "objectGroup" used to control the

packages/flutter/test/foundation/service_extensions_test.dart

@@ -26,6 +26,8 @@ class TestServiceExtensionsBinding extends BindingBase
 
   final Map<String, ServiceExtensionCallback> extensions = <String, ServiceExtensionCallback>{};
 
+  final Map<String, List<Map<String, dynamic>>> eventsDispatched = <String, List<Map<String, dynamic>>>{};
+
   @override
   void registerServiceExtension({
     @required String name,
@@ -35,6 +37,20 @@ class TestServiceExtensionsBinding extends BindingBase
     extensions[name] = callback;
   }
 
+  @override
+  void postEvent(String eventKind, Map<dynamic, dynamic> eventData) {
+    getEventsDispatched(eventKind).add(eventData);
+  }
+
+  List<Map<String, dynamic>> getEventsDispatched(String eventKind) {
+    return eventsDispatched.putIfAbsent(eventKind, () => <Map<String, dynamic>>[]);
+  }
+
+  Iterable<Map<String, dynamic>> getServiceExtensionStateChangedEvents(String extensionName) {
+    return getEventsDispatched('Flutter.ServiceExtensionStateChanged')
+      .where((Map<String, dynamic> event) => event['extension'] == extensionName);
+  }
+
   Future<Map<String, dynamic>> testExtension(String name, Map<String, String> arguments) {
     expect(extensions.containsKey(name), isTrue);
     return extensions[name](arguments);
@@ -228,6 +244,8 @@ void main() {
   });
 
   test('Service extensions - debugPaint', () async {
+    final Iterable<Map<String, dynamic>> extensionChangedEvents = binding.getServiceExtensionStateChangedEvents('ext.flutter.debugPaint');
+    Map<String, dynamic> extensionChangedEvent;
     Map<String, dynamic> result;
     Future<Map<String, dynamic>> pendingResult;
     bool completed;
@@ -237,6 +255,7 @@ void main() {
     result = await binding.testExtension('debugPaint', <String, String>{});
     expect(result, <String, String>{ 'enabled': 'false' });
     expect(debugPaintSizeEnabled, false);
+    expect(extensionChangedEvents, isEmpty);
     expect(binding.frameScheduled, isFalse);
     pendingResult = binding.testExtension('debugPaint', <String, String>{ 'enabled': 'true' });
     completed = false;
@@ -251,9 +270,14 @@ void main() {
     result = await pendingResult;
     expect(result, <String, String>{ 'enabled': 'true' });
     expect(debugPaintSizeEnabled, true);
+    expect(extensionChangedEvents.length, 1);
+    extensionChangedEvent = extensionChangedEvents.last;
+    expect(extensionChangedEvent['extension'], 'ext.flutter.debugPaint');
+    expect(extensionChangedEvent['value'], 'true');
     result = await binding.testExtension('debugPaint', <String, String>{});
     expect(result, <String, String>{ 'enabled': 'true' });
     expect(debugPaintSizeEnabled, true);
+    expect(extensionChangedEvents.length, 1);
     expect(binding.frameScheduled, isFalse);
     pendingResult = binding.testExtension('debugPaint', <String, String>{ 'enabled': 'false' });
     await binding.flushMicrotasks();
@@ -263,9 +287,14 @@ void main() {
     result = await pendingResult;
     expect(result, <String, String>{ 'enabled': 'false' });
     expect(debugPaintSizeEnabled, false);
+    expect(extensionChangedEvents.length, 2);
+    extensionChangedEvent = extensionChangedEvents.last;
+    expect(extensionChangedEvent['extension'], 'ext.flutter.debugPaint');
+    expect(extensionChangedEvent['value'], 'false');
     result = await binding.testExtension('debugPaint', <String, String>{});
     expect(result, <String, String>{ 'enabled': 'false' });
     expect(debugPaintSizeEnabled, false);
+    expect(extensionChangedEvents.length, 2);
     expect(binding.frameScheduled, isFalse);
   });
 
@@ -373,6 +402,8 @@ void main() {
   });
 
   test('Service extensions - platformOverride', () async {
+    final Iterable<Map<String, dynamic>> extensionChangedEvents = binding.getServiceExtensionStateChangedEvents('ext.flutter.platformOverride');
+    Map<String, dynamic> extensionChangedEvent;
     Map<String, dynamic> result;
 
     expect(binding.reassembled, 0);
@@ -380,30 +411,55 @@ void main() {
     result = await binding.testExtension('platformOverride', <String, String>{});
     expect(result, <String, String>{'value': 'android'});
     expect(defaultTargetPlatform, TargetPlatform.android);
+    expect(extensionChangedEvents, isEmpty);
     result = await hasReassemble(binding.testExtension('platformOverride', <String, String>{'value': 'iOS'}));
     expect(result, <String, String>{'value': 'iOS'});
     expect(binding.reassembled, 1);
     expect(defaultTargetPlatform, TargetPlatform.iOS);
+    expect(extensionChangedEvents.length, 1);
+    extensionChangedEvent = extensionChangedEvents.last;
+    expect(extensionChangedEvent['extension'], 'ext.flutter.platformOverride');
+    expect(extensionChangedEvent['value'], 'iOS');
     result = await hasReassemble(binding.testExtension('platformOverride', <String, String>{'value': 'android'}));
     expect(result, <String, String>{'value': 'android'});
     expect(binding.reassembled, 2);
     expect(defaultTargetPlatform, TargetPlatform.android);
+    expect(extensionChangedEvents.length, 2);
+    extensionChangedEvent = extensionChangedEvents.last;
+    expect(extensionChangedEvent['extension'], 'ext.flutter.platformOverride');
+    expect(extensionChangedEvent['value'], 'android');
     result = await hasReassemble(binding.testExtension('platformOverride', <String, String>{'value': 'fuchsia'}));
     expect(result, <String, String>{'value': 'fuchsia'});
     expect(binding.reassembled, 3);
     expect(defaultTargetPlatform, TargetPlatform.fuchsia);
+    expect(extensionChangedEvents.length, 3);
+    extensionChangedEvent = extensionChangedEvents.last;
+    expect(extensionChangedEvent['extension'], 'ext.flutter.platformOverride');
+    expect(extensionChangedEvent['value'], 'fuchsia');
     result = await hasReassemble(binding.testExtension('platformOverride', <String, String>{'value': 'default'}));
     expect(result, <String, String>{'value': 'android'});
     expect(binding.reassembled, 4);
     expect(defaultTargetPlatform, TargetPlatform.android);
+    expect(extensionChangedEvents.length, 4);
+    extensionChangedEvent = extensionChangedEvents.last;
+    expect(extensionChangedEvent['extension'], 'ext.flutter.platformOverride');
+    expect(extensionChangedEvent['value'], 'android');
     result = await hasReassemble(binding.testExtension('platformOverride', <String, String>{'value': 'iOS'}));
     expect(result, <String, String>{'value': 'iOS'});
     expect(binding.reassembled, 5);
     expect(defaultTargetPlatform, TargetPlatform.iOS);
+    expect(extensionChangedEvents.length, 5);
+    extensionChangedEvent = extensionChangedEvents.last;
+    expect(extensionChangedEvent['extension'], 'ext.flutter.platformOverride');
+    expect(extensionChangedEvent['value'], 'iOS');
     result = await hasReassemble(binding.testExtension('platformOverride', <String, String>{'value': 'bogus'}));
     expect(result, <String, String>{'value': 'android'});
     expect(binding.reassembled, 6);
     expect(defaultTargetPlatform, TargetPlatform.android);
+    expect(extensionChangedEvents.length, 6);
+    extensionChangedEvent = extensionChangedEvents.last;
+    expect(extensionChangedEvent['extension'], 'ext.flutter.platformOverride');
+    expect(extensionChangedEvent['value'], 'android');
     binding.reassembled = 0;
   });
 
@@ -518,6 +574,8 @@ void main() {
   });
 
   test('Service extensions - timeDilation', () async {
+    final Iterable<Map<String, dynamic>> extensionChangedEvents = binding.getServiceExtensionStateChangedEvents('ext.flutter.timeDilation');
+    Map<String, dynamic> extensionChangedEvent;
     Map<String, dynamic> result;
 
     expect(binding.frameScheduled, isFalse);
@@ -525,18 +583,29 @@ void main() {
     result = await binding.testExtension('timeDilation', <String, String>{});
     expect(result, <String, String>{ 'timeDilation': '1.0' });
     expect(timeDilation, 1.0);
+    expect(extensionChangedEvents, isEmpty);
     result = await binding.testExtension('timeDilation', <String, String>{ 'timeDilation': '100.0' });
     expect(result, <String, String>{ 'timeDilation': '100.0' });
     expect(timeDilation, 100.0);
+    expect(extensionChangedEvents.length, 1);
+    extensionChangedEvent = extensionChangedEvents.last;
+    expect(extensionChangedEvent['extension'], 'ext.flutter.timeDilation');
+    expect(extensionChangedEvent['value'], '100.0');
     result = await binding.testExtension('timeDilation', <String, String>{});
     expect(result, <String, String>{ 'timeDilation': '100.0' });
     expect(timeDilation, 100.0);
+    expect(extensionChangedEvents.length, 1);
     result = await binding.testExtension('timeDilation', <String, String>{ 'timeDilation': '1.0' });
     expect(result, <String, String>{ 'timeDilation': '1.0' });
     expect(timeDilation, 1.0);
+    expect(extensionChangedEvents.length, 2);
+    extensionChangedEvent = extensionChangedEvents.last;
+    expect(extensionChangedEvent['extension'], 'ext.flutter.timeDilation');
+    expect(extensionChangedEvent['value'], '1.0');
     result = await binding.testExtension('timeDilation', <String, String>{});
     expect(result, <String, String>{ 'timeDilation': '1.0' });
     expect(timeDilation, 1.0);
+    expect(extensionChangedEvents.length, 2);
     expect(binding.frameScheduled, isFalse);
   });
 

packages/flutter/test/widgets/widget_inspector_test.dart

@@ -194,8 +194,7 @@ void main() {
 class TestWidgetInspectorService extends Object with WidgetInspectorService {
   final Map<String, InspectorServiceExtensionCallback> extensions = <String, InspectorServiceExtensionCallback>{};
 
-  final Map<String, List<Map<Object, Object>>> eventsDispatched =
-      <String, List<Map<Object, Object>>>{};
+  final Map<String, List<Map<Object, Object>>> eventsDispatched = <String, List<Map<Object, Object>>>{};
 
   @override
   void registerServiceExtension({
@@ -215,6 +214,11 @@ class TestWidgetInspectorService extends Object with WidgetInspectorService {
     return eventsDispatched.putIfAbsent(eventKind, () => <Map<Object, Object>>[]);
   }
 
+  Iterable<Map<Object, Object>> getServiceExtensionStateChangedEvents(String extensionName) {
+    return getEventsDispatched('Flutter.ServiceExtensionStateChanged')
+      .where((Map<Object, Object> event) => event['extension'] == extensionName);
+  }
+
   Future<Object> testExtension(String name, Map<String, String> arguments) async {
     expect(extensions.containsKey(name), isTrue);
     // Encode and decode to JSON to match behavior using a real service
@@ -1725,15 +1729,33 @@ class TestWidgetInspectorService extends Object with WidgetInspectorService {
     }, skip: !WidgetInspectorService.instance.isWidgetCreationTracked()); // Test requires --track-widget-creation flag.
 
     testWidgets('ext.flutter.inspector.show', (WidgetTester tester) async {
+      final Iterable<Map<Object, Object>> extensionChangedEvents = service.getServiceExtensionStateChangedEvents('ext.flutter.inspector.show');
+      Map<Object, Object> extensionChangedEvent;
+
       service.rebuildCount = 0;
+      expect(extensionChangedEvents, isEmpty);
       expect(await service.testBoolExtension('show', <String, String>{'enabled': 'true'}), equals('true'));
+      expect(extensionChangedEvents.length, equals(1));
+      extensionChangedEvent = extensionChangedEvents.last;
+      expect(extensionChangedEvent['extension'], equals('ext.flutter.inspector.show'));
+      expect(extensionChangedEvent['value'], isTrue);
       expect(service.rebuildCount, equals(1));
       expect(await service.testBoolExtension('show', <String, String>{}), equals('true'));
       expect(WidgetsApp.debugShowWidgetInspectorOverride, isTrue);
+      expect(extensionChangedEvents.length, equals(1));
       expect(await service.testBoolExtension('show', <String, String>{'enabled': 'true'}), equals('true'));
+      expect(extensionChangedEvents.length, equals(2));
+      extensionChangedEvent = extensionChangedEvents.last;
+      expect(extensionChangedEvent['extension'], equals('ext.flutter.inspector.show'));
+      expect(extensionChangedEvent['value'], isTrue);
       expect(service.rebuildCount, equals(1));
       expect(await service.testBoolExtension('show', <String, String>{'enabled': 'false'}), equals('false'));
+      expect(extensionChangedEvents.length, equals(3));
+      extensionChangedEvent = extensionChangedEvents.last;
+      expect(extensionChangedEvent['extension'], equals('ext.flutter.inspector.show'));
+      expect(extensionChangedEvent['value'], isFalse);
       expect(await service.testBoolExtension('show', <String, String>{}), equals('false'));
+      expect(extensionChangedEvents.length, equals(3));
       expect(service.rebuildCount, equals(2));
       expect(WidgetsApp.debugShowWidgetInspectorOverride, isFalse);
     });