Address previous comments, fix Intent.doNothing.

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

@@ -29,11 +29,10 @@ class Intent extends Diagnosticable {
 
   /// An intent that can't be mapped to an action.
   ///
-  /// This Intent is prevented from being mapped to an action in the
-  /// [ActionDispatcher], and as such can be used to indicate that a shortcut
-  /// should not do anything, allowing a shortcut defined at a higher level to
-  /// be disabled at a deeper level in the widget hierarchy.
-  static const Intent doNothing = Intent(ValueKey<Type>(Intent));
+  /// This Intent is mapped to an action in the [WidgetsApp] that does nothing,
+  /// so that it can be bound to a key in a [Shortcuts] widget in order to
+  /// disable a key binding made above it in the hierarchy.
+  static const Intent doNothing = DoNothingIntent();
 
   /// The key for the action this intent is associated with.
   final LocalKey key;
@@ -224,6 +223,7 @@ class Actions extends InheritedWidget {
         // Stop visiting.
         return false;
       }
+
       element.visitAncestorElements(visitAncestorElement);
     }
     return dispatcher ?? const ActionDispatcher();
@@ -278,9 +278,6 @@ class Actions extends InheritedWidget {
   ///
   /// Setting `nullOk` to true means that if no ambient [Actions] widget is
   /// found, then this method will return false instead of throwing.
-  ///
-  /// If the `intent` argument is [Intent.doNothing], then this function will
-  /// return false, without looking for a matching action.
   static bool invoke(
     BuildContext context,
     Intent intent, {
@@ -292,10 +289,6 @@ class Actions extends InheritedWidget {
     Element actionsElement;
     Action action;
 
-    if (identical(intent, Intent.doNothing)) {
-      return false;
-    }
-
     bool visitAncestorElement(Element element) {
       if (element.widget is! Actions) {
         // Continue visiting.
@@ -358,3 +351,29 @@ class Actions extends InheritedWidget {
     properties.add(DiagnosticsProperty<Map<LocalKey, ActionFactory>>('actions', actions));
   }
 }
+
+/// An [Action], that, as the name implies, does nothing.
+///
+/// This action is bound to the [Intent.doNothing] intent inside of
+/// [WidgetsApp.build] so that a [Shortcuts] widget can bind a key to it to
+/// override another shortcut binding defined above it in the hierarchy.
+class DoNothingAction extends Action {
+  /// Const constructor for [DoNothingAction].
+  const DoNothingAction() : super(key);
+
+  /// The Key used for the [DoNothingIntent] intent, and registered at the top
+  /// level actions in [WidgetsApp.build].
+  static const LocalKey key = ValueKey<Type>(DoNothingAction);
+
+  @override
+  void invoke(FocusNode node, Intent invocation) { }
+}
+
+/// An [Intent] that can be used to disable [Shortcuts] key bindings defined
+/// above a widget in the hierarchy.
+///
+/// The [Intent.doNothing] intent is of this type.
+class DoNothingIntent extends Intent {
+  /// Const constructor for [DoNothingIntent].
+  const DoNothingIntent() : super(DoNothingAction.key);
+}

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

@@ -8,6 +8,7 @@ import 'dart:collection' show HashMap;
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 
+import 'actions.dart';
 import 'banner.dart';
 import 'basic.dart';
 import 'binding.dart';
@@ -1194,14 +1195,19 @@ class _WidgetsAppState extends State<WidgetsApp> implements WidgetsBindingObserv
 
     assert(_debugCheckLocalizations(appLocale));
 
-    return DefaultFocusTraversal(
-      policy: ReadingOrderTraversalPolicy(),
-      child: MediaQuery(
-        data: MediaQueryData.fromWindow(WidgetsBinding.instance.window),
-        child: Localizations(
-          locale: appLocale,
-          delegates: _localizationsDelegates.toList(),
-          child: title,
+    return Actions(
+      actions: <LocalKey, ActionFactory>{
+        DoNothingAction.key: () => const DoNothingAction(),
+      },
+      child: DefaultFocusTraversal(
+        policy: ReadingOrderTraversalPolicy(),
+        child: MediaQuery(
+          data: MediaQueryData.fromWindow(WidgetsBinding.instance.window),
+          child: Localizations(
+            locale: appLocale,
+            delegates: _localizationsDelegates.toList(),
+            child: title,
+          ),
         ),
       ),
     );

packages/flutter/test/widgets/actions_test.dart

@@ -302,11 +302,11 @@ void main() {
       ).debugFillProperties(builder);
 
       final List<String> description = builder.properties
-          .where((DiagnosticsNode node) {
-            return !node.isFiltered(DiagnosticLevel.info);
-          })
-          .map((DiagnosticsNode node) => node.toString())
-          .toList();
+        .where((DiagnosticsNode node) {
+          return !node.isFiltered(DiagnosticLevel.info);
+        })
+        .map((DiagnosticsNode node) => node.toString())
+        .toList();
 
       expect(description[0], equalsIgnoringHashCodes('dispatcher: ActionDispatcher#00000'));
       expect(description[1], equals('actions: {}'));

packages/flutter/test/widgets/shortcuts_test.dart

@@ -37,22 +37,6 @@ class TestIntent extends Intent {
   const TestIntent() : super(TestAction.key);
 }
 
-class DoNothingAction extends Action {
-  const DoNothingAction({
-    @required OnInvokeCallback onInvoke,
-  })  : assert(onInvoke != null),
-        super(key);
-
-  static const LocalKey key = ValueKey<Type>(DoNothingAction);
-
-  @override
-  void invoke(FocusNode node, Intent invocation) {}
-}
-
-class DoNothingIntent extends Intent {
-  const DoNothingIntent() : super(DoNothingAction.key);
-}
-
 class TestShortcutManager extends ShortcutManager {
   TestShortcutManager(this.keys);
 
@@ -143,8 +127,8 @@ void main() {
         LogicalKeyboardKey.keyD,
         LogicalKeyboardKey.keyC,
         LogicalKeyboardKey.keyB,
-        LogicalKeyboardKey.keyA,}
-      );
+        LogicalKeyboardKey.keyA,
+      });
       final Map<LogicalKeySet, String> map = <LogicalKeySet, String>{set1: 'one'};
       expect(set2 == set3, isTrue);
       expect(set2 == set4, isTrue);
@@ -192,10 +176,12 @@ void main() {
       await tester.pumpWidget(
         Actions(
           actions: <LocalKey, ActionFactory>{
-            TestAction.key: () => TestAction(onInvoke: (FocusNode node, Intent intent) {
-              invoked = true;
-              return true;
-            }),
+            TestAction.key: () => TestAction(
+              onInvoke: (FocusNode node, Intent intent) {
+                invoked = true;
+                return true;
+              },
+            ),
           },
           child: Shortcuts(
             manager: testManager,
@@ -228,14 +214,16 @@ void main() {
           },
           child: Actions(
             actions: <LocalKey, ActionFactory>{
-              TestAction.key: () => TestAction(onInvoke: (FocusNode node, Intent intent) {
-                invoked = true;
-                return true;
-              }),
+              TestAction.key: () => TestAction(
+                onInvoke: (FocusNode node, Intent intent) {
+                  invoked = true;
+                  return true;
+                },
+              ),
             },
             child: Shortcuts(
               shortcuts: <LogicalKeySet, Intent>{
-                LogicalKeySet(LogicalKeyboardKey.keyA): const DoNothingIntent(),
+                LogicalKeySet(LogicalKeyboardKey.keyA): Intent.doNothing,
               },
               child: Focus(
                 autofocus: true,
@@ -251,5 +239,45 @@ void main() {
       expect(invoked, isTrue);
       expect(pressedKeys, equals(<LogicalKeyboardKey>[LogicalKeyboardKey.shiftLeft]));
     });
+    testWidgets('$Shortcuts can disable a shortcut with Intent.doNothing', (WidgetTester tester) async {
+      final GlobalKey containerKey = GlobalKey();
+      final List<LogicalKeyboardKey> pressedKeys = <LogicalKeyboardKey>[];
+      final TestShortcutManager testManager = TestShortcutManager(pressedKeys);
+      bool invoked = false;
+      await tester.pumpWidget(
+        MaterialApp(
+          home: Shortcuts(
+            manager: testManager,
+            shortcuts: <LogicalKeySet, Intent>{
+              LogicalKeySet(LogicalKeyboardKey.shift): const TestIntent(),
+            },
+            child: Actions(
+              actions: <LocalKey, ActionFactory>{
+                TestAction.key: () => TestAction(
+                  onInvoke: (FocusNode node, Intent intent) {
+                    invoked = true;
+                    return true;
+                  },
+                ),
+              },
+              child: Shortcuts(
+                shortcuts: <LogicalKeySet, Intent>{
+                  LogicalKeySet(LogicalKeyboardKey.shift): Intent.doNothing,
+                },
+                child: Focus(
+                  autofocus: true,
+                  child: Container(key: containerKey, width: 100, height: 100),
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+      await tester.pump();
+      expect(Shortcuts.of(containerKey.currentContext), isNotNull);
+      await tester.sendKeyDownEvent(LogicalKeyboardKey.shiftLeft);
+      expect(invoked, isFalse);
+      expect(pressedKeys, isEmpty);
+    });
   });
 }