Exclude modal barrier from semantics on Android (#11024)

* Exclude modal barrier from semantics on Android

* Add tests

packages/flutter/lib/src/material/drawer.dart

@@ -272,6 +272,8 @@ class DrawerControllerState extends State<DrawerController> with SingleTickerPro
             children: <Widget>[
               new BlockSemantics(
                 child: new GestureDetector(
+                  // On Android, the back button is used to dismiss a modal.
+                  excludeFromSemantics: defaultTargetPlatform == TargetPlatform.android,
                   onTap: close,
                   child: new Container(
                     color: _color.evaluate(_controller)

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

@@ -2,6 +2,8 @@
 // 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 'basic.dart';
 import 'container.dart';
 import 'framework.dart';
@@ -28,7 +30,8 @@ class ModalBarrier extends StatelessWidget {
   Widget build(BuildContext context) {
     return new BlockSemantics(
       child: new ExcludeSemantics(
-        excluding: !dismissible,
+        // On Android, the back button is used to dismiss a modal.
+        excluding: !dismissible || defaultTargetPlatform == TargetPlatform.android,
         child: new Semantics(
           container: true,
           child: new GestureDetector(

packages/flutter/test/material/dialog_test.dart

@@ -212,7 +212,7 @@ void main() {
       ),
     );
 
-    expect(semantics, includesNodeWithLabel(buttonText));
+    expect(semantics, includesNodeWith(label: buttonText));
 
     final BuildContext context = tester.element(find.text(buttonText));
 
@@ -224,8 +224,8 @@ void main() {
 
     await tester.pumpAndSettle(const Duration(seconds: 1));
 
-    expect(semantics, includesNodeWithLabel(alertText));
-    expect(semantics, isNot(includesNodeWithLabel(buttonText)));
+    expect(semantics, includesNodeWith(label: alertText));
+    expect(semantics, isNot(includesNodeWith(label: buttonText)));
 
     semantics.dispose();
   });

packages/flutter/test/material/scaffold_test.dart

@@ -459,22 +459,22 @@ void main() {
       drawer: new Drawer(child:new Semantics(label: drawerLabel, child: new Container())),
     )));
 
-    expect(semantics, includesNodeWithLabel(bodyLabel));
-    expect(semantics, includesNodeWithLabel(persistentFooterButtonLabel));
-    expect(semantics, includesNodeWithLabel(bottomNavigationBarLabel));
-    expect(semantics, includesNodeWithLabel(floatingActionButtonLabel));
-    expect(semantics, isNot(includesNodeWithLabel(drawerLabel)));
+    expect(semantics, includesNodeWith(label: bodyLabel));
+    expect(semantics, includesNodeWith(label: persistentFooterButtonLabel));
+    expect(semantics, includesNodeWith(label: bottomNavigationBarLabel));
+    expect(semantics, includesNodeWith(label: floatingActionButtonLabel));
+    expect(semantics, isNot(includesNodeWith(label: drawerLabel)));
 
     final ScaffoldState state = tester.firstState(find.byType(Scaffold));
     state.openDrawer();
     await tester.pump();
     await tester.pump(const Duration(seconds: 1));
 
-    expect(semantics, isNot(includesNodeWithLabel(bodyLabel)));
-    expect(semantics, isNot(includesNodeWithLabel(persistentFooterButtonLabel)));
-    expect(semantics, isNot(includesNodeWithLabel(bottomNavigationBarLabel)));
-    expect(semantics, isNot(includesNodeWithLabel(floatingActionButtonLabel)));
-    expect(semantics, includesNodeWithLabel(drawerLabel));
+    expect(semantics, isNot(includesNodeWith(label: bodyLabel)));
+    expect(semantics, isNot(includesNodeWith(label: persistentFooterButtonLabel)));
+    expect(semantics, isNot(includesNodeWith(label: bottomNavigationBarLabel)));
+    expect(semantics, isNot(includesNodeWith(label: floatingActionButtonLabel)));
+    expect(semantics, includesNodeWith(label: drawerLabel));
 
     semantics.dispose();
   });

packages/flutter/test/widgets/drawer_test.dart

@@ -3,9 +3,13 @@
 // found in the LICENSE file.
 
 import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 
+import 'semantics_tester.dart';
+
 void main() {
 
   testWidgets('Drawer control test', (WidgetTester tester) async {
@@ -172,4 +176,60 @@ void main() {
     expect(buttonPressed, equals(true));
   });
 
+  testWidgets('Dismissible ModalBarrier includes button in semantic tree on iOS', (WidgetTester tester) async {
+    debugDefaultTargetPlatformOverride = TargetPlatform.iOS;
+
+    final SemanticsTester semantics = new SemanticsTester(tester);
+    final GlobalKey<ScaffoldState> scaffoldKey = new GlobalKey<ScaffoldState>();
+
+    await tester.pumpWidget(
+        new MaterialApp(
+            home: new Builder(
+                builder: (BuildContext context) {
+                  return new Scaffold(
+                      key: scaffoldKey,
+                      drawer: const Drawer(),
+                  );
+                }
+            )
+        )
+    );
+
+    // Open the drawer.
+    scaffoldKey.currentState.openDrawer();
+    await tester.pump(const Duration(milliseconds: 100));
+
+    expect(semantics, includesNodeWith(actions: <SemanticsAction>[SemanticsAction.tap]));
+
+    semantics.dispose();
+
+    debugDefaultTargetPlatformOverride = null;
+  });
+
+  testWidgets('Dismissible ModalBarrier is hidden on Android (back button is used to dismiss)', (WidgetTester tester) async {
+    final SemanticsTester semantics = new SemanticsTester(tester);
+    final GlobalKey<ScaffoldState> scaffoldKey = new GlobalKey<ScaffoldState>();
+
+    await tester.pumpWidget(
+        new MaterialApp(
+            home: new Builder(
+                builder: (BuildContext context) {
+                  return new Scaffold(
+                      key: scaffoldKey,
+                      drawer: const Drawer(),
+                      body: new Container()
+                  );
+                }
+            )
+        )
+    );
+
+    // Open the drawer.
+    scaffoldKey.currentState.openDrawer();
+    await tester.pump(const Duration(milliseconds: 100));
+
+    expect(semantics, isNot(includesNodeWith(actions: <SemanticsAction>[SemanticsAction.tap])));
+
+    semantics.dispose();
+  });
 }

packages/flutter/test/widgets/modal_barrier_test.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
@@ -92,7 +93,9 @@ void main() {
     semantics.dispose();
   });
 
-  testWidgets('Dismissible ModalBarrier includes button in semantic tree', (WidgetTester tester) async {
+  testWidgets('Dismissible ModalBarrier includes button in semantic tree on iOS', (WidgetTester tester) async {
+    debugDefaultTargetPlatformOverride = TargetPlatform.iOS;
+
     final SemanticsTester semantics = new SemanticsTester(tester);
     await tester.pumpWidget(const ModalBarrier(dismissible: true));
 
@@ -113,6 +116,17 @@ void main() {
     );
     expect(semantics, hasSemantics(expectedSemantics));
 
+    semantics.dispose();
+    debugDefaultTargetPlatformOverride = null;
+  });
+
+  testWidgets('Dismissible ModalBarrier is hidden on Android (back button is used to dismiss)', (WidgetTester tester) async {
+    final SemanticsTester semantics = new SemanticsTester(tester);
+    await tester.pumpWidget(const ModalBarrier(dismissible: true));
+
+    final TestSemantics expectedSemantics = new TestSemantics.root();
+    expect(semantics, hasSemantics(expectedSemantics));
+
     semantics.dispose();
   });
 }

packages/flutter/test/widgets/semantics_9_test.dart

@@ -28,7 +28,7 @@ void main() {
         ],
       ));
 
-      expect(semantics, isNot(includesNodeWithLabel('layer#1')));
+      expect(semantics, isNot(includesNodeWith(label: 'layer#1')));
 
       await tester.pumpWidget(new Stack(
         children: <Widget>[
@@ -39,7 +39,7 @@ void main() {
         ],
       ));
 
-      expect(semantics, includesNodeWithLabel('layer#1'));
+      expect(semantics, includesNodeWith(label: 'layer#1'));
 
       semantics.dispose();
     });
@@ -86,13 +86,13 @@ void main() {
         ],
       ));
 
-      expect(semantics, includesNodeWithLabel('#1'));
-      expect(semantics, includesNodeWithLabel('#2'));
-      expect(semantics, isNot(includesNodeWithLabel('NOT#2.1')));
-      expect(semantics, includesNodeWithLabel('#2.2'));
-      expect(semantics, includesNodeWithLabel('#2.2.1'));
-      expect(semantics, includesNodeWithLabel('#2.3'));
-      expect(semantics, includesNodeWithLabel('#3'));
+      expect(semantics, includesNodeWith(label: '#1'));
+      expect(semantics, includesNodeWith(label: '#2'));
+      expect(semantics, isNot(includesNodeWith(label:'NOT#2.1')));
+      expect(semantics, includesNodeWith(label: '#2.2'));
+      expect(semantics, includesNodeWith(label: '#2.2.1'));
+      expect(semantics, includesNodeWith(label: '#2.3'));
+      expect(semantics, includesNodeWith(label: '#3'));
 
       semantics.dispose();
     });
@@ -121,9 +121,9 @@ void main() {
         ],
       ));
 
-      expect(semantics, isNot(includesNodeWithLabel('NOT#1')));
-      expect(semantics, includesNodeWithLabel('#2.1'));
-      expect(semantics, includesNodeWithLabel('#3'));
+      expect(semantics, isNot(includesNodeWith(label: 'NOT#1')));
+      expect(semantics, includesNodeWith(label: '#2.1'));
+      expect(semantics, includesNodeWith(label: '#3'));
 
       semantics.dispose();
     });

packages/flutter/test/widgets/semantics_tester.dart

@@ -240,17 +240,21 @@ class _HasSemantics extends Matcher {
 /// Asserts that a [SemanticsTester] has a semantics tree that exactly matches the given semantics.
 Matcher hasSemantics(TestSemantics semantics) => new _HasSemantics(semantics);
 
-class _IncludesNodeWithLabel extends Matcher {
-  const _IncludesNodeWithLabel(this._label) : assert(_label != null);
+class _IncludesNodeWith extends Matcher {
+  const _IncludesNodeWith({
+    this.label,
+    this.actions,
+}) : assert(label != null || actions != null);
 
-  final String _label;
+  final String label;
+  final List<SemanticsAction> actions;
 
   @override
   bool matches(covariant SemanticsTester item, Map<dynamic, dynamic> matchState) {
     bool result = false;
     SemanticsNodeVisitor visitor;
     visitor = (SemanticsNode node) {
-      if (node.label == _label) {
+      if (checkNode(node)) {
         result = true;
       } else {
         node.visitChildren(visitor);
@@ -262,16 +266,43 @@ class _IncludesNodeWithLabel extends Matcher {
     return result;
   }
 
+  bool checkNode(SemanticsNode node) {
+    if (label != null && node.label != label)
+      return false;
+    if (actions != null) {
+      final int expectedActions = actions.fold(0, (int value, SemanticsAction action) => value | action.index);
+      final int actualActions = node.getSemanticsData().actions;
+      if (expectedActions != actualActions)
+        return false;
+    }
+    return true;
+  }
+
   @override
   Description describe(Description description) {
-    return description.add('includes node with label "$_label"');
+    return description.add('includes node with $_configAsString');
   }
 
   @override
   Description describeMismatch(dynamic item, Description mismatchDescription, Map<dynamic, dynamic> matchState, bool verbose) {
-    return mismatchDescription.add('could not find node with label "$_label".\n$_matcherHelp');
+    return mismatchDescription.add('could not find node with $_configAsString.\n$_matcherHelp');
+  }
+
+  String get _configAsString {
+    String string = '';
+    if (label != null) {
+      string += 'label "$label"';
+      if (actions != null)
+        string += ' and ';
+    }
+    if (actions != null) {
+      string += ' actions "${actions.join(', ')}"';
+    }
+    return string;
   }
 }
 
-/// Asserts that a node in the semantics tree of [SemanticsTester] has [label].
-Matcher includesNodeWithLabel(String label) => new _IncludesNodeWithLabel(label);
+/// Asserts that a node in the semantics tree of [SemanticsTester] has [label] and [actions].
+///
+/// If `null` is provided for either argument it will match against any value.
+Matcher includesNodeWith({ String label, List<SemanticsAction> actions }) => new _IncludesNodeWith(label: label, actions: actions);