Fix a legacy TODO (#77454)

dev/integration_tests/web_e2e_tests/test_driver/text_editing_integration.dart

@@ -3,8 +3,10 @@
 // found in the LICENSE file.
 
 // @dart = 2.9
+
 import 'dart:html';
 import 'dart:js_util' as js_util;
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -21,9 +23,6 @@ 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);
@@ -49,9 +48,6 @@ 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);
@@ -77,9 +73,6 @@ 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'));
@@ -113,9 +106,6 @@ 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);
@@ -148,9 +138,6 @@ 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);
@@ -198,9 +185,6 @@ 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);

packages/flutter_test/lib/src/binding.dart

@@ -195,9 +195,15 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
 
   /// Called by the test framework at the beginning of a widget test to
   /// prepare the binding for the next test.
+  ///
+  /// If [registerTestTextInput] returns true when this method is called,
+  /// the [testTextInput] is configured to simulate the keyboard.
   void reset() {
     _restorationManager = null;
     resetGestureBinding();
+    testTextInput.reset();
+    if (registerTestTextInput)
+      _testTextInput.register();
   }
 
   @override
@@ -237,7 +243,8 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
   @protected
   bool get overrideHttpClient => true;
 
-  /// Determines whether the binding automatically registers [testTextInput].
+  /// Determines whether the binding automatically registers [testTextInput] as
+  /// a fake keyboard implementation.
   ///
   /// Unit tests make use of this to mock out text input communication for
   /// widgets. An integration test would set this to false, to test real IME
@@ -245,6 +252,19 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
   ///
   /// [TestTextInput.isRegistered] reports whether the text input mock is
   /// registered or not.
+  ///
+  /// Some of the properties and methods on [testTextInput] are only valid if
+  /// [registerTestTextInput] returns true when a test starts. If those
+  /// members are accessed when using a binding that sets this flag to false,
+  /// they will throw.
+  ///
+  /// If this property returns true when a test ends, the [testTextInput] is
+  /// unregistered.
+  ///
+  /// This property should not change the value it returns during the lifetime
+  /// of the binding. Changing the value of this property risks very confusing
+  /// behavior as the [TestTextInput] may be inconsistently registered or
+  /// unregistered.
   @protected
   bool get registerTestTextInput => true;
 
@@ -319,9 +339,6 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
       binding.setupHttpOverrides();
     }
     _testTextInput = TestTextInput(onCleared: _resetFocusedEditable);
-    if (registerTestTextInput) {
-      _testTextInput.register();
-    }
   }
 
   @override
@@ -799,6 +816,8 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
       // alone so that we don't cause more spurious errors.
       runApp(Container(key: UniqueKey(), child: _postTestMessage)); // Unmount any remaining widgets.
       await pump();
+      if (registerTestTextInput)
+        _testTextInput.unregister();
       invariantTester();
       _verifyAutoUpdateGoldensUnset(autoUpdateGoldensBeforeTest && !isBrowser);
       _verifyReportTestExceptionUnset(reportTestExceptionBeforeTest);

packages/flutter_test/lib/src/test_text_input.dart

@@ -15,6 +15,18 @@ export 'package:flutter/services.dart' show TextEditingValue, TextInputAction;
 ///
 /// Typical app tests will not need to use this class directly.
 ///
+/// The [TestWidgetsFlutterBinding] class registers a [TestTextInput] instance
+/// ([TestWidgetsFlutterBinding.testTextInput]) as a stub keyboard
+/// implementation if its [TestWidgetsFlutterBinding.registerTestTextInput]
+/// property returns true when a test starts, and unregisters it when the test
+/// ends (unless it ends with a failure).
+///
+/// See [register], [unregister], and [isRegistered] for details.
+///
+/// The [updateEditingValue], [enterText], and [receiveAction] methods can be
+/// used even when the [TestTextInput] is not registered. All other methods
+/// will assert if [isRegistered] is false.
+///
 /// See also:
 ///
 /// * [WidgetTester.enterText], which uses this class to simulate keyboard input.
@@ -37,37 +49,43 @@ class TestTextInput {
   /// The messenger which sends the bytes for this channel, not null.
   BinaryMessenger get _binaryMessenger => ServicesBinding.instance!.defaultBinaryMessenger;
 
-  /// Resets any internal state of this object and calls [register].
+  /// Log for method calls.
+  ///
+  /// For all registered channels, handled calls are added to the list. Can
+  /// be cleaned using `log.clear()`.
+  final List<MethodCall> log = <MethodCall>[];
+
+  /// Resets any internal state of this object.
   ///
   /// This method is invoked by the testing framework between tests. It should
   /// not ordinarily be called by tests directly.
-  void resetAndRegister() {
+  void reset() {
     log.clear();
     editingState = null;
     setClientArgs = null;
     _client = 0;
     _isVisible = false;
-    register();
   }
+
   /// Installs this object as a mock handler for [SystemChannels.textInput].
+  ///
+  /// Called by the binding at the top of a test when
+  /// [TestWidgetsFlutterBinding.registerTestTextInput] is true.
   void register() => SystemChannels.textInput.setMockMethodCallHandler(_handleTextInputCall);
 
   /// Removes this object as a mock handler for [SystemChannels.textInput].
   ///
   /// After calling this method, the channel will exchange messages with the
-  /// Flutter engine. Use this with [FlutterDriver] tests that need to display
-  /// on-screen keyboard provided by the operating system.
-  void unregister() => SystemChannels.textInput.setMockMethodCallHandler(null);
-
-  /// Log for method calls.
+  /// Flutter engine instead of the stub.
   ///
-  /// For all registered channels, handled calls are added to the list. Can
-  /// be cleaned using `log.clear()`.
-  final List<MethodCall> log = <MethodCall>[];
+  /// Called by the binding at the end of a (successful) test when
+  /// [TestWidgetsFlutterBinding.registerTestTextInput] is true.
+  void unregister() => SystemChannels.textInput.setMockMethodCallHandler(null);
 
   /// Whether this [TestTextInput] is registered with [SystemChannels.textInput].
   ///
-  /// Use [register] and [unregister] methods to control this value.
+  /// The binding uses the [register] and [unregister] methods to control this
+  /// value when [TestWidgetsFlutterBinding.registerTestTextInput] is true.
   bool get isRegistered => SystemChannels.textInput.checkMockMethodCallHandler(_handleTextInputCall);
 
   /// Whether there are any active clients listening to text input.
@@ -78,11 +96,13 @@ class TestTextInput {
 
   int _client = 0;
 
-  /// Arguments supplied to the TextInput.setClient method call.
+  /// The last set of arguments supplied to the `TextInput.setClient` and
+  /// `TextInput.updateConfig` methods of this stub implementation.
   Map<String, dynamic>? setClientArgs;
 
   /// The last set of arguments that [TextInputConnection.setEditingState] sent
-  /// to the embedder.
+  /// to this stub implementation (i.e. the arguments set to
+  /// `TextInput.setEditingState`).
   ///
   /// This is a map representation of a [TextEditingValue] object. For example,
   /// it will have a `text` entry whose value matches the most recent
@@ -118,15 +138,27 @@ class TestTextInput {
   }
 
   /// Whether the onscreen keyboard is visible to the user.
+  ///
+  /// Specifically, this reflects the last call to `TextInput.show` or
+  /// `TextInput.hide` received by the stub implementation.
   bool get isVisible {
     assert(isRegistered);
     return _isVisible;
   }
   bool _isVisible = false;
 
+  /// Simulates the user hiding the onscreen keyboard.
+  ///
+  /// This does nothing but set the internal flag.
+  void hide() {
+    assert(isRegistered);
+    _isVisible = false;
+  }
+
   /// Simulates the user changing the [TextEditingValue] to the given value.
+  ///
+  /// This can be called even if the [TestTextInput] has not been [register]ed.
   void updateEditingValue(TextEditingValue value) {
-    assert(isRegistered);
     // Not using the `expect` function because in the case of a FlutterDriver
     // test this code does not run in a package:test test zone.
     if (_client == 0)
@@ -146,6 +178,7 @@ class TestTextInput {
   /// Simulates the user closing the text input connection.
   ///
   /// For example:
+  ///
   /// - User pressed the home button and sent the application to background.
   /// - User closed the virtual keyboard.
   void closeConnection() {
@@ -167,8 +200,9 @@ class TestTextInput {
   }
 
   /// Simulates the user typing the given text.
+  ///
+  /// This can be called even if the [TestTextInput] has not been [register]ed.
   void enterText(String text) {
-    assert(isRegistered);
     updateEditingValue(TextEditingValue(
       text: text,
     ));
@@ -177,8 +211,9 @@ class TestTextInput {
   /// Simulates the user pressing one of the [TextInputAction] buttons.
   /// Does not check that the [TextInputAction] performed is an acceptable one
   /// based on the `inputAction` [setClientArgs].
+  ///
+  /// This can be called even if the [TestTextInput] has not been [register]ed.
   Future<void> receiveAction(TextInputAction action) async {
-    assert(isRegistered);
     return TestAsyncUtils.guard(() {
       // Not using the `expect` function because in the case of a FlutterDriver
       // test this code does not run in a package:test test zone.
@@ -216,10 +251,4 @@ class TestTextInput {
       return completer.future;
     });
   }
-
-  /// Simulates the user hiding the onscreen keyboard.
-  void hide() {
-    assert(isRegistered);
-    _isVisible = false;
-  }
 }

packages/flutter_test/lib/src/widget_tester.dart

@@ -136,7 +136,6 @@ void testWidgets(
           () async {
             binding.reset();
             debugResetSemanticsIdCounter();
-            tester.resetTestTextInput();
             Object? memento;
             try {
               memento = await variant.setUp(value);
@@ -989,18 +988,13 @@ class WidgetTester extends WidgetController implements HitTestDispatcher, Ticker
   ///
   /// Typical app tests will not need to use this value. To add text to widgets
   /// like [TextField] or [TextFormField], call [enterText].
-  TestTextInput get testTextInput => binding.testTextInput;
-
-  /// Ensures that [testTextInput] is registered and [TestTextInput.log] is
-  /// reset.
   ///
-  /// This is called by the testing framework before test runs, so that if a
-  /// previous test has set its own handler on [SystemChannels.textInput], the
-  /// [testTextInput] regains control and the log is fresh for the new test.
-  /// It should not typically need to be called by tests.
-  void resetTestTextInput() {
-    testTextInput.resetAndRegister();
-  }
+  /// Some of the properties and methods on this value are only valid if the
+  /// binding's [TestWidgetsFlutterBinding.registerTestTextInput] flag is set to
+  /// true as a test is starting (meaning that the keyboard is to be simulated
+  /// by the test framework). If those members are accessed when using a binding
+  /// that sets this flag to false, they will throw.
+  TestTextInput get testTextInput => binding.testTextInput;
 
   /// Give the text input widget specified by [finder] the focus, as if the
   /// onscreen keyboard had appeared.

packages/flutter_test/test/bindings_test.dart

@@ -11,6 +11,8 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:test_api/test_api.dart' as test_package;
 
 void main() {
+  final AutomatedTestWidgetsFlutterBinding binding = AutomatedTestWidgetsFlutterBinding();
+
   group(TestViewConfiguration, () {
     test('is initialized with top-level window if one is not provided', () {
       // The code below will throw without the default.
@@ -20,15 +22,32 @@ void main() {
 
   group(AutomatedTestWidgetsFlutterBinding, () {
     test('allows setting defaultTestTimeout to 5 minutes', () {
-      final AutomatedTestWidgetsFlutterBinding binding = AutomatedTestWidgetsFlutterBinding();
       binding.defaultTestTimeout = const test_package.Timeout(Duration(minutes: 5));
       expect(binding.defaultTestTimeout.duration, const Duration(minutes: 5));
     });
   });
 
+  // The next three tests must run in order -- first using `test`, then `testWidgets`, then `test` again.
+
+  int order = 0;
+
   test('Initializes httpOverrides and testTextInput', () async {
-    final TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized() as TestWidgetsFlutterBinding;
-    expect(binding.testTextInput.isRegistered, true);
+    assert(order == 0);
+    expect(binding.testTextInput, isNotNull);
+    expect(binding.testTextInput.isRegistered, isFalse);
     expect(HttpOverrides.current, isNotNull);
+    order += 1;
+  });
+
+  testWidgets('Registers testTextInput', (WidgetTester tester) async {
+    assert(order == 1);
+    expect(tester.testTextInput.isRegistered, isTrue);
+    order += 1;
+  });
+
+  test('Unregisters testTextInput', () async {
+    assert(order == 2);
+    expect(binding.testTextInput.isRegistered, isFalse);
+    order += 1;
   });
 }