Migrate to ChannelBuffers.push (flutter#81235)

Author: Hixie

dev/automated_tests/flutter_test/ticker_test.dart

@@ -11,6 +11,6 @@ void main() {
     Ticker((Duration duration) { }).start();
 
     final ByteData? message = const StringCodec().encodeMessage('AppLifecycleState.paused');
-    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', message, (_) {});
+    await tester.binding.defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', message, (_) {});
   });
 }

dev/integration_tests/web_e2e_tests/test_driver/text_editing_integration.dart

@@ -20,9 +20,6 @@ void main() {
     app.main();
     await tester.pumpAndSettle();
 
-    // TODO(nurhan): https://github.com/flutter/flutter/issues/51885
-    SystemChannels.textInput.setMockMethodCallHandler(null);
-
     // Focus on a TextFormField.
     final Finder finder = find.byKey(const Key('input'));
     expect(finder, findsOneWidget);
@@ -48,9 +45,6 @@ void main() {
     app.main();
     await tester.pumpAndSettle();
 
-    // TODO(nurhan): https://github.com/flutter/flutter/issues/51885
-    SystemChannels.textInput.setMockMethodCallHandler(null);
-
     // Focus on a TextFormField.
     final Finder finder = find.byKey(const Key('empty-input'));
     expect(finder, findsOneWidget);
@@ -76,9 +70,6 @@ void main() {
     app.main();
     await tester.pumpAndSettle();
 
-    // TODO(nurhan): https://github.com/flutter/flutter/issues/51885
-    SystemChannels.textInput.setMockMethodCallHandler(null);
-
     // This text will show no-enter initially. It will have 'enter-pressed'
     // after `onFieldSubmitted` of TextField is triggered.
     final Finder textFinder = find.byKey(const Key('text'));
@@ -112,9 +103,6 @@ void main() {
     app.main();
     await tester.pumpAndSettle();
 
-    // TODO(nurhan): https://github.com/flutter/flutter/issues/51885
-    SystemChannels.textInput.setMockMethodCallHandler(null);
-
     // Focus on a TextFormField.
     final Finder finder = find.byKey(const Key('input'));
     expect(finder, findsOneWidget);
@@ -147,9 +135,6 @@ void main() {
     app.main();
     await tester.pumpAndSettle();
 
-    // TODO(nurhan): https://github.com/flutter/flutter/issues/51885
-    SystemChannels.textInput.setMockMethodCallHandler(null);
-
     // Focus on a TextFormField.
     final Finder finder = find.byKey(const Key('input'));
     expect(finder, findsOneWidget);
@@ -197,9 +182,6 @@ void main() {
     app.main();
     await tester.pumpAndSettle();
 
-    // TODO(nurhan): https://github.com/flutter/flutter/issues/51885
-    SystemChannels.textInput.setMockMethodCallHandler(null);
-
     // Select something from the selectable text.
     final Finder finder = find.byKey(const Key('selectable'));
     expect(finder, findsOneWidget);

examples/hello_world/test_driver/smoke_web_engine_test.dart

@@ -5,7 +5,7 @@
 import 'dart:async';
 
 import 'package:flutter_driver/flutter_driver.dart';
-import 'package:test/test.dart' hide TypeMatcher, isInstanceOf;
+import 'package:test/test.dart';
 import 'package:webdriver/async_io.dart';
 
 /// The following test is used as a simple smoke test for verifying Flutter
@@ -33,6 +33,7 @@ void main() {
     test('enable accessibility', () async {
       await driver.enableAccessibility();
 
+      // TODO(ianh): this delay violates our style guide. We should instead wait for a triggering event.
       await Future<void>.delayed(const Duration(seconds: 2));
 
       // Elements with tag "flt-semantics" would show up after enabling

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

@@ -104,8 +104,8 @@ abstract class BindingBase {
   /// A number of additional bindings are defined as extensions of
   /// [BindingBase], e.g., [ServicesBinding], [RendererBinding], and
   /// [WidgetsBinding]. Each of these bindings define behaviors that interact
-  /// with a [ui.PlatformDispatcher], e.g., [ServicesBinding] registers a
-  /// [ui.PlatformDispatcher.onPlatformMessage] handler, and [RendererBinding]
+  /// with a [ui.PlatformDispatcher], e.g., [ServicesBinding] registers
+  /// listeners with the [ChannelBuffers], and [RendererBinding]
   /// registers [ui.PlatformDispatcher.onMetricsChanged],
   /// [ui.PlatformDispatcher.onTextScaleFactorChanged],
   /// [ui.PlatformDispatcher.onSemanticsEnabledChanged], and

packages/flutter/lib/src/services/binary_messenger.dart

@@ -2,12 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-
 import 'dart:typed_data';
 import 'dart:ui' as ui;
 
-import 'binding.dart';
-
 /// A function which takes a platform message and asynchronously returns an encoded response.
 typedef MessageHandler = Future<ByteData?>? Function(ByteData? message);
 
@@ -19,12 +16,39 @@ abstract class BinaryMessenger {
   /// const constructors so that they can be used in const expressions.
   const BinaryMessenger();
 
-  /// Calls the handler registered for the given channel.
+  /// Queues a message.
+  ///
+  /// The returned future completes immediately.
+  ///
+  /// This method adds the provided message to the given channel (named by the
+  /// `channel` argument) of the [ChannelBuffers] object. This simulates what
+  /// happens when a plugin on the platform thread (e.g. Kotlin or Swift code)
+  /// sends a message to the plugin package on the Dart thread.
+  ///
+  /// The `data` argument contains the message as encoded bytes. (The format
+  /// used for the message depends on the channel.)
   ///
-  /// Typically called by [ServicesBinding] to handle platform messages received
-  /// from [dart:ui.PlatformDispatcher.onPlatformMessage].
+  /// The `callback` argument, if non-null, is eventually invoked with the
+  /// response that would have been sent to the platform thread.
+  ///
+  /// In production code, it is more efficient to call
+  /// `ServicesBinding.instance.channelBuffers.push` directly.
+  ///
+  /// In tests, consider using
+  /// `tester.binding.defaultBinaryMessenger.handlePlatformMessage` (see
+  /// [WidgetTester], [TestWidgetsFlutterBinding], [TestDefaultBinaryMessenger],
+  /// and [TestDefaultBinaryMessenger.handlePlatformMessage] respectively).
   ///
   /// To register a handler for a given message channel, see [setMessageHandler].
+  ///
+  /// To send a message _to_ a plugin on the platform thread, see [send].
+  // TODO(ianh): deprecate this method once cocoon and other customer_tests are migrated:
+  // @NotYetDeprecated(
+  //   'Instead of calling this method, use ServicesBinding.instance.channelBuffers.push. '
+  //   'In tests, consider using tester.binding.defaultBinaryMessenger.handlePlatformMessage '
+  //   'or TestDefaultBinaryMessenger.instance.defaultBinaryMessenger.handlePlatformMessage. '
+  //   'This feature was deprecated after v2.1.0-10.0.pre.'
+  // )
   Future<void> handlePlatformMessage(String channel, ByteData? data, ui.PlatformMessageResponseCallback? callback);
 
   /// Send a binary message to the platform plugins on the given channel.
@@ -43,37 +67,6 @@ abstract class BinaryMessenger {
   /// The handler's return value, if non-null, is sent as a response, unencoded.
   void setMessageHandler(String channel, MessageHandler? handler);
 
-  /// Returns true if the `handler` argument matches the `handler` previously
-  /// passed to [setMessageHandler].
-  ///
-  /// This method is useful for tests or test harnesses that want to assert the
-  /// handler for the specified channel has not been altered by a previous test.
-  ///
-  /// Passing null for the `handler` returns true if the handler for the
-  /// `channel` is not set.
-  bool checkMessageHandler(String channel, MessageHandler? handler);
-
-  /// Set a mock callback for intercepting messages from the [send] method on
-  /// this class, on the given channel, without decoding them.
-  ///
-  /// The given callback will replace the currently registered mock callback for
-  /// that channel, if any. To remove the mock handler, pass null as the
-  /// `handler` argument.
-  ///
-  /// The handler's return value, if non-null, is used as a response, unencoded.
-  ///
-  /// This is intended for testing. Messages intercepted in this manner are not
-  /// sent to platform plugins.
-  void setMockMessageHandler(String channel, MessageHandler? handler);
-
-  /// Returns true if the `handler` argument matches the `handler` previously
-  /// passed to [setMockMessageHandler].
-  ///
-  /// This method is useful for tests or test harnesses that want to assert the
-  /// mock handler for the specified channel has not been altered by a previous
-  /// test.
-  ///
-  /// Passing null for the `handler` returns true if the handler for the
-  /// `channel` is not set.
-  bool checkMockMessageHandler(String channel, MessageHandler? handler);
+  // Looking for setMockMessageHandler or checkMockMessageHandler?
+  // See this shim package: packages/flutter_test/lib/src/deprecated.dart
 }

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

@@ -30,7 +30,6 @@ mixin ServicesBinding on BindingBase, SchedulerBinding {
     _instance = this;
     _defaultBinaryMessenger = createBinaryMessenger();
     _restorationManager = createRestorationManager();
-    window.onPlatformMessage = defaultBinaryMessenger.handlePlatformMessage;
     initLicenses();
     SystemChannels.system.setMessageHandler((dynamic message) => handleSystemMessage(message as Object));
     SystemChannels.lifecycle.setMessageHandler(_handleLifecycleMessage);
@@ -49,14 +48,35 @@ mixin ServicesBinding on BindingBase, SchedulerBinding {
   BinaryMessenger get defaultBinaryMessenger => _defaultBinaryMessenger;
   late BinaryMessenger _defaultBinaryMessenger;
 
+  /// The low level buffering and dispatch mechanism for messages sent by
+  /// plugins on the engine side to their corresponding plugin code on
+  /// the framework side.
+  ///
+  /// This exposes the [dart:ui.channelBuffers] object. Bindings can override
+  /// this getter to intercept calls to the [ChannelBuffers] mechanism (for
+  /// example, for tests).
+  ///
+  /// In production, direct access to this object should not be necessary.
+  /// Messages are received and dispatched by the [defaultBinaryMessenger]. This
+  /// object is primarily used to send mock messages in tests, via the
+  /// [ChannelBuffers.push] method (simulating a plugin sending a message to the
+  /// framework).
+  ///
+  /// See also:
+  ///
+  ///  * [PlatformDispatcher.sendPlatformMessage], which is used for sending
+  ///    messages to plugins from the framework (the opposite of
+  ///    [channelBuffers]).
+  ///  * [platformDispatcher], the [PlatformDispatcher] singleton.
+  ui.ChannelBuffers get channelBuffers => ui.channelBuffers;
+
   /// Creates a default [BinaryMessenger] instance that can be used for sending
   /// platform messages.
   @protected
   BinaryMessenger createBinaryMessenger() {
     return const _DefaultBinaryMessenger._();
   }
 
-
   /// Called when the operating system notifies the application of a memory
   /// pressure situation.
   ///
@@ -253,17 +273,20 @@ mixin ServicesBinding on BindingBase, SchedulerBinding {
 class _DefaultBinaryMessenger extends BinaryMessenger {
   const _DefaultBinaryMessenger._();
 
-  // Handlers for incoming messages from platform plugins.
-  // This is static so that this class can have a const constructor.
-  static final Map<String, MessageHandler> _handlers =
-      <String, MessageHandler>{};
-
-  // Mock handlers that intercept and respond to outgoing messages.
-  // This is static so that this class can have a const constructor.
-  static final Map<String, MessageHandler> _mockHandlers =
-      <String, MessageHandler>{};
+  @override
+  Future<void> handlePlatformMessage(
+    String channel,
+    ByteData? message,
+    ui.PlatformMessageResponseCallback? callback,
+  ) async {
+    ui.channelBuffers.push(channel, message, (ByteData? data) {
+      if (callback != null)
+        callback(data);
+    });
+  }
 
-  Future<ByteData?> _sendPlatformMessage(String channel, ByteData? message) {
+  @override
+  Future<ByteData?> send(String channel, ByteData? message) {
     final Completer<ByteData?> completer = Completer<ByteData?>();
     // ui.PlatformDispatcher.instance is accessed directly instead of using
     // ServicesBinding.instance.platformDispatcher because this method might be
@@ -272,6 +295,8 @@ class _DefaultBinaryMessenger extends BinaryMessenger {
     // ui.PlatformDispatcher.instance because the PlatformDispatcher may be
     // dependency injected elsewhere with a different instance. However, static
     // access at this location seems to be the least bad option.
+    // TODO(ianh): Use ServicesBinding.instance once we have better diagnostics
+    // on that getter.
     ui.PlatformDispatcher.instance.sendPlatformMessage(channel, message, (ByteData? reply) {
       try {
         completer.complete(reply);
@@ -287,70 +312,27 @@ class _DefaultBinaryMessenger extends BinaryMessenger {
     return completer.future;
   }
 
-  @override
-  // TODO(goderbauer): Add pragma (and enable test in
-  //   break_on_framework_exceptions_test.dart) when it works on async methods,
-  //   https://github.com/dart-lang/sdk/issues/45673
-  // @pragma('vm:notify-debugger-on-exception')
-  Future<void> handlePlatformMessage(
-    String channel,
-    ByteData? data,
-    ui.PlatformMessageResponseCallback? callback,
-  ) async {
-    ByteData? response;
-    try {
-      final MessageHandler? handler = _handlers[channel];
-      if (handler != null) {
-        response = await handler(data);
-      } else {
-        ui.channelBuffers.push(channel, data, callback!);
-        callback = null;
-      }
-    } catch (exception, stack) {
-      FlutterError.reportError(FlutterErrorDetails(
-        exception: exception,
-        stack: stack,
-        library: 'services library',
-        context: ErrorDescription('during a platform message callback'),
-      ));
-    } finally {
-      if (callback != null) {
-        callback(response);
-      }
-    }
-  }
-
-  @override
-  Future<ByteData?>? send(String channel, ByteData? message) {
-    final MessageHandler? handler = _mockHandlers[channel];
-    if (handler != null)
-      return handler(message);
-    return _sendPlatformMessage(channel, message);
-  }
-
   @override
   void setMessageHandler(String channel, MessageHandler? handler) {
     if (handler == null) {
-      _handlers.remove(channel);
+      ui.channelBuffers.clearListener(channel);
     } else {
-      _handlers[channel] = handler;
-      ui.channelBuffers.drain(channel, (ByteData? data, ui.PlatformMessageResponseCallback callback) async {
-        await handlePlatformMessage(channel, data, callback);
+      ui.channelBuffers.setListener(channel, (ByteData? data, ui.PlatformMessageResponseCallback callback) async {
+        ByteData? response;
+        try {
+          response = await handler(data);
+        } catch (exception, stack) {
+
+          FlutterError.reportError(FlutterErrorDetails(
+            exception: exception,
+            stack: stack,
+            library: 'services library',
+            context: ErrorDescription('during a platform message callback'),
+          ));
+        } finally {
+          callback(response);
+        }
       });
     }
   }
-
-  @override
-  bool checkMessageHandler(String channel, MessageHandler? handler) => _handlers[channel] == handler;
-
-  @override
-  void setMockMessageHandler(String channel, MessageHandler? handler) {
-    if (handler == null)
-      _mockHandlers.remove(channel);
-    else
-      _mockHandlers[channel] = handler;
-  }
-
-  @override
-  bool checkMockMessageHandler(String channel, MessageHandler? handler) => _mockHandlers[channel] == handler;
 }

packages/flutter/lib/src/services/message_codec.dart

@@ -95,7 +95,6 @@ abstract class MethodCodec {
   ByteData encodeErrorEnvelope({ required String code, String? message, Object? details});
 }
 
-
 /// Thrown to indicate that a platform interaction failed in the platform
 /// plugin.
 ///