Reland "Adds a parent scope TraversalEdgeBehavior and fixes modal rou… (#134554)

…… (#134550)"

fixes https://github.com/flutter/flutter/issues/112567

This reverts commit 5900c4ba.

The internal test needs migration. cl/564746935

This is the same of original pr, no new change

## Pre-launch Checklist

- [ ] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [ ] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [ ] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [ ] I signed the [CLA].
- [ ] I listed at least one issue that this PR fixes in the description
above.
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [ ] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [ ] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[Features we expect every widget to implement]:
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[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat

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

@@ -1683,6 +1683,7 @@ class _WidgetsAppState extends State<WidgetsApp> with WidgetsBindingObserver {
             },
           onUnknownRoute: _onUnknownRoute,
           observers: widget.navigatorObservers!,
+          routeTraversalEdgeBehavior: kIsWeb ? TraversalEdgeBehavior.leaveFlutterView : TraversalEdgeBehavior.parentScope,
           reportsRouteUpdateToEngine: true,
         ),
       );

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

@@ -120,6 +120,16 @@ enum TraversalEdgeBehavior {
   /// address bar, escape an `iframe`, or focus on HTML elements other than
   /// those managed by Flutter.
   leaveFlutterView,
+
+  /// Allows focus to traverse up to parent scope.
+  ///
+  /// When reaching the edge of the current scope, requesting the next focus
+  /// will look up to the parent scope of the current scope and focus the focus
+  /// node next to the current scope.
+  ///
+  /// If there is no parent scope above the current scope, fallback to
+  /// [closedLoop] behavior.
+  parentScope,
 }
 
 /// Determines how focusable widgets are traversed within a [FocusTraversalGroup].
@@ -186,6 +196,60 @@ abstract class FocusTraversalPolicy with Diagnosticable {
     );
   }
 
+  /// Request focus on a focus node as a result of a tab traversal.
+  ///
+  /// If the `node` is a [FocusScopeNode], this method will recursively find
+  /// the next focus from its descendants until it find a regular [FocusNode].
+  ///
+  /// Returns true if this method focused a new focus node.
+  bool _requestTabTraversalFocus(
+    FocusNode node, {
+    ScrollPositionAlignmentPolicy? alignmentPolicy,
+    double? alignment,
+    Duration? duration,
+    Curve? curve,
+    required bool forward,
+  }) {
+    if (node is FocusScopeNode) {
+      if (node.focusedChild != null) {
+        // Can't stop here as the `focusedChild` may be a focus scope node
+        // without a first focus. The first focus will be picked in the
+        // next iteration.
+        return _requestTabTraversalFocus(
+          node.focusedChild!,
+          alignmentPolicy: alignmentPolicy,
+          alignment: alignment,
+          duration: duration,
+          curve: curve,
+          forward: forward,
+        );
+      }
+      final List<FocusNode> sortedChildren = _sortAllDescendants(node, node);
+      if (sortedChildren.isNotEmpty) {
+        _requestTabTraversalFocus(
+          forward ? sortedChildren.first : sortedChildren.last,
+          alignmentPolicy: alignmentPolicy,
+          alignment: alignment,
+          duration: duration,
+          curve: curve,
+          forward: forward,
+        );
+        // Regardless if _requestTabTraversalFocus return true or false, a first
+        // focus has been picked.
+        return true;
+      }
+    }
+    final bool nodeHadPrimaryFocus = node.hasPrimaryFocus;
+    requestFocusCallback(
+      node,
+      alignmentPolicy: alignmentPolicy,
+      alignment: alignment,
+      duration: duration,
+      curve: curve,
+    );
+    return !nodeHadPrimaryFocus;
+  }
+
   /// Returns the node that should receive focus if focus is traversing
   /// forwards, and there is no current focus.
   ///
@@ -340,10 +404,21 @@ abstract class FocusTraversalPolicy with Diagnosticable {
   @protected
   Iterable<FocusNode> sortDescendants(Iterable<FocusNode> descendants, FocusNode currentNode);
 
-  Map<FocusNode?, _FocusTraversalGroupInfo> _findGroups(FocusScopeNode scope, _FocusTraversalGroupNode? scopeGroupNode, FocusNode currentNode) {
+  static Iterable<FocusNode> _getDescendantsWithoutExpandingScope(FocusNode node) {
+    final List<FocusNode> result = <FocusNode>[];
+    for (final FocusNode child in node.children) {
+      if (child is! FocusScopeNode) {
+        result.addAll(_getDescendantsWithoutExpandingScope(child));
+      }
+      result.add(child);
+    }
+    return result;
+  }
+
+  static Map<FocusNode?, _FocusTraversalGroupInfo> _findGroups(FocusScopeNode scope, _FocusTraversalGroupNode? scopeGroupNode, FocusNode currentNode) {
     final FocusTraversalPolicy defaultPolicy = scopeGroupNode?.policy ?? ReadingOrderTraversalPolicy();
     final Map<FocusNode?, _FocusTraversalGroupInfo> groups = <FocusNode?, _FocusTraversalGroupInfo>{};
-    for (final FocusNode node in scope.descendants) {
+    for (final FocusNode node in _getDescendantsWithoutExpandingScope(scope)) {
       final _FocusTraversalGroupNode? groupNode = FocusTraversalGroup._getGroupNode(node);
       // Group nodes need to be added to their parent's node, or to the "null"
       // node if no parent is found. This creates the hierarchy of group nodes
@@ -376,7 +451,7 @@ abstract class FocusTraversalPolicy with Diagnosticable {
 
   // Sort all descendants, taking into account the FocusTraversalGroup
   // that they are each in, and filtering out non-traversable/focusable nodes.
-  List<FocusNode> _sortAllDescendants(FocusScopeNode scope, FocusNode currentNode) {
+  static List<FocusNode> _sortAllDescendants(FocusScopeNode scope, FocusNode currentNode) {
     final _FocusTraversalGroupNode? scopeGroupNode = FocusTraversalGroup._getGroupNode(scope);
     // Build the sorting data structure, separating descendants into groups.
     final Map<FocusNode?, _FocusTraversalGroupInfo> groups = _findGroups(scope, scopeGroupNode, currentNode);
@@ -463,30 +538,42 @@ abstract class FocusTraversalPolicy with Diagnosticable {
     if (focusedChild == null) {
       final FocusNode? firstFocus = forward ? findFirstFocus(currentNode) : findLastFocus(currentNode);
       if (firstFocus != null) {
-        requestFocusCallback(
+        return _requestTabTraversalFocus(
           firstFocus,
           alignmentPolicy: forward ? ScrollPositionAlignmentPolicy.keepVisibleAtEnd : ScrollPositionAlignmentPolicy.keepVisibleAtStart,
+          forward: forward,
         );
-        return true;
       }
     }
     focusedChild ??= nearestScope;
     final List<FocusNode> sortedNodes = _sortAllDescendants(nearestScope, focusedChild);
-
     assert(sortedNodes.contains(focusedChild));
-    if (sortedNodes.length < 2) {
-      // If there are no nodes to traverse to, like when descendantsAreTraversable
-      // is false or skipTraversal for all the nodes is true.
-      return false;
-    }
+
     if (forward && focusedChild == sortedNodes.last) {
       switch (nearestScope.traversalEdgeBehavior) {
         case TraversalEdgeBehavior.leaveFlutterView:
           focusedChild.unfocus();
           return false;
+        case TraversalEdgeBehavior.parentScope:
+          final FocusScopeNode? parentScope = nearestScope.enclosingScope;
+          if (parentScope != null && parentScope != FocusManager.instance.rootScope) {
+            focusedChild.unfocus();
+            parentScope.nextFocus();
+            // Verify the focus really has changed.
+            return focusedChild.enclosingScope?.focusedChild != focusedChild;
+          }
+          // No valid parent scope. Fallback to closed loop behavior.
+          return _requestTabTraversalFocus(
+            sortedNodes.first,
+            alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtEnd,
+            forward: forward,
+          );
         case TraversalEdgeBehavior.closedLoop:
-          requestFocusCallback(sortedNodes.first, alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtEnd);
-          return true;
+          return _requestTabTraversalFocus(
+            sortedNodes.first,
+            alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtEnd,
+            forward: forward,
+          );
       }
     }
     if (!forward && focusedChild == sortedNodes.first) {
@@ -494,9 +581,26 @@ abstract class FocusTraversalPolicy with Diagnosticable {
         case TraversalEdgeBehavior.leaveFlutterView:
           focusedChild.unfocus();
           return false;
+        case TraversalEdgeBehavior.parentScope:
+          final FocusScopeNode? parentScope = nearestScope.enclosingScope;
+          if (parentScope != null && parentScope != FocusManager.instance.rootScope) {
+            focusedChild.unfocus();
+            parentScope.previousFocus();
+            // Verify the focus really has changed.
+            return focusedChild.enclosingScope?.focusedChild != focusedChild;
+          }
+          // No valid parent scope. Fallback to closed loop behavior.
+          return _requestTabTraversalFocus(
+            sortedNodes.last,
+            alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtStart,
+            forward: forward,
+          );
         case TraversalEdgeBehavior.closedLoop:
-          requestFocusCallback(sortedNodes.last, alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtStart);
-          return true;
+          return _requestTabTraversalFocus(
+            sortedNodes.last,
+            alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtStart,
+            forward: forward,
+          );
       }
     }
 
@@ -504,11 +608,11 @@ abstract class FocusTraversalPolicy with Diagnosticable {
     FocusNode? previousNode;
     for (final FocusNode node in maybeFlipped) {
       if (previousNode == focusedChild) {
-        requestFocusCallback(
+        return _requestTabTraversalFocus(
           node,
           alignmentPolicy: forward ? ScrollPositionAlignmentPolicy.keepVisibleAtEnd : ScrollPositionAlignmentPolicy.keepVisibleAtStart,
+          forward: forward,
         );
-        return true;
       }
       previousNode = node;
     }

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

@@ -1144,9 +1144,7 @@ class DefaultTransitionDelegate<T> extends TransitionDelegate<T> {
 /// The default value of [Navigator.routeTraversalEdgeBehavior].
 ///
 /// {@macro flutter.widgets.navigator.routeTraversalEdgeBehavior}
-const TraversalEdgeBehavior kDefaultRouteTraversalEdgeBehavior = kIsWeb
-  ? TraversalEdgeBehavior.leaveFlutterView
-  : TraversalEdgeBehavior.closedLoop;
+const TraversalEdgeBehavior kDefaultRouteTraversalEdgeBehavior = TraversalEdgeBehavior.parentScope;
 
 /// A widget that manages a set of child widgets with a stack discipline.
 ///

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

@@ -834,7 +834,9 @@ class _ModalScopeState<T> extends State<_ModalScope<T>> {
   late Listenable _listenable;
 
   /// The node this scope will use for its root [FocusScope] widget.
-  final FocusScopeNode focusScopeNode = FocusScopeNode(debugLabel: '$_ModalScopeState Focus Scope');
+  final FocusScopeNode focusScopeNode = FocusScopeNode(
+    debugLabel: '$_ModalScopeState Focus Scope',
+  );
   final ScrollController primaryScrollController = ScrollController();
 
   @override
@@ -936,6 +938,8 @@ class _ModalScopeState<T> extends State<_ModalScope<T>> {
                     controller: primaryScrollController,
                     child: FocusScope(
                       node: focusScopeNode, // immutable
+                      // Only top most route can participate in focus traversal.
+                      skipTraversal: !widget.route.isCurrent,
                       child: RepaintBoundary(
                         child: AnimatedBuilder(
                           animation: _listenable, // immutable
@@ -1704,11 +1708,26 @@ abstract class ModalRoute<T> extends TransitionRoute<T> with LocalHistoryRoute<T
     changedInternalState();
   }
 
+  @override
+  void didChangeNext(Route<dynamic>? nextRoute) {
+    super.didChangeNext(nextRoute);
+    changedInternalState();
+  }
+
+  @override
+  void didPopNext(Route<dynamic> nextRoute) {
+    super.didPopNext(nextRoute);
+    changedInternalState();
+  }
+
   @override
   void changedInternalState() {
     super.changedInternalState();
-    setState(() { /* internal state already changed */ });
-    _modalBarrier.markNeedsBuild();
+    // No need to mark dirty if this method is called during build phase.
+    if (SchedulerBinding.instance.schedulerPhase != SchedulerPhase.persistentCallbacks) {
+      setState(() { /* internal state already changed */ });
+      _modalBarrier.markNeedsBuild();
+    }
     _modalScope.maintainState = maintainState;
   }
 

packages/flutter/test/material/icon_button_test.dart

@@ -4,6 +4,7 @@
 
 import 'dart:ui';
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -792,6 +793,10 @@ void main() {
   testWidgetsWithLeakTracking("Disabled IconButton can't be traversed to when disabled.", (WidgetTester tester) async {
     final FocusNode focusNode1 = FocusNode(debugLabel: 'IconButton 1');
     final FocusNode focusNode2 = FocusNode(debugLabel: 'IconButton 2');
+    addTearDown(() {
+      focusNode1.dispose();
+      focusNode2.dispose();
+    });
 
     await tester.pumpWidget(
       wrap(
@@ -821,11 +826,8 @@ void main() {
     expect(focusNode1.nextFocus(), isFalse);
     await tester.pump();
 
-    expect(focusNode1.hasPrimaryFocus, isTrue);
+    expect(focusNode1.hasPrimaryFocus, !kIsWeb);
     expect(focusNode2.hasPrimaryFocus, isFalse);
-
-    focusNode1.dispose();
-    focusNode2.dispose();
   });
 
   group('feedback', () {

packages/flutter/test/widgets/actions_test.dart

@@ -981,7 +981,7 @@ void main() {
         expect(buttonNode2.hasFocus, isFalse);
         primaryFocus!.nextFocus();
         await tester.pump();
-        expect(buttonNode1.hasFocus, isTrue);
+        expect(buttonNode1.hasFocus, isFalse);
         expect(buttonNode2.hasFocus, isFalse);
       },
     );

packages/flutter/test/widgets/focus_traversal_test.dart

@@ -441,6 +441,96 @@ void main() {
 
   });
 
+  testWidgetsWithLeakTracking('Nested navigator does not trap focus', (WidgetTester tester) async {
+    final FocusNode node1 = FocusNode();
+    addTearDown(node1.dispose);
+    final FocusNode node2 = FocusNode();
+    addTearDown(node2.dispose);
+    final FocusNode node3 = FocusNode();
+    addTearDown(node3.dispose);
+
+    await tester.pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: FocusTraversalGroup(
+          policy: ReadingOrderTraversalPolicy(),
+          child: FocusScope(
+            child: Column(
+              children: <Widget>[
+                Focus(
+                  focusNode: node1,
+                  child: const SizedBox(width: 100, height: 100),
+                ),
+                SizedBox(
+                  width: 100,
+                  height: 100,
+                  child: Navigator(
+                    pages: <Page<void>>[
+                      MaterialPage<void>(
+                        child: Focus(
+                          focusNode: node2,
+                          child: const SizedBox(width: 100, height: 100),
+                        ),
+                      ),
+                    ],
+                    onPopPage: (_, __) => false,
+                  ),
+                ),
+                Focus(
+                  focusNode: node3,
+                  child: const SizedBox(width: 100, height: 100),
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+
+    node1.requestFocus();
+    await tester.pump();
+
+    expect(node1.hasFocus, isTrue);
+    expect(node2.hasFocus, isFalse);
+    expect(node3.hasFocus, isFalse);
+
+    node1.nextFocus();
+    await tester.pump();
+    expect(node1.hasFocus, isFalse);
+    expect(node2.hasFocus, isTrue);
+    expect(node3.hasFocus, isFalse);
+
+    node2.nextFocus();
+    await tester.pump();
+    expect(node1.hasFocus, isFalse);
+    expect(node2.hasFocus, isFalse);
+    expect(node3.hasFocus, isTrue);
+
+    node3.nextFocus();
+    await tester.pump();
+    expect(node1.hasFocus, isTrue);
+    expect(node2.hasFocus, isFalse);
+    expect(node3.hasFocus, isFalse);
+
+    node1.previousFocus();
+    await tester.pump();
+    expect(node1.hasFocus, isFalse);
+    expect(node2.hasFocus, isFalse);
+    expect(node3.hasFocus, isTrue);
+
+    node3.previousFocus();
+    await tester.pump();
+    expect(node1.hasFocus, isFalse);
+    expect(node2.hasFocus, isTrue);
+    expect(node3.hasFocus, isFalse);
+
+    node2.previousFocus();
+    await tester.pump();
+    expect(node1.hasFocus, isTrue);
+    expect(node2.hasFocus, isFalse);
+    expect(node3.hasFocus, isFalse);
+  });
+
   group(ReadingOrderTraversalPolicy, () {
     testWidgetsWithLeakTracking('Find the initial focus if there is none yet.', (WidgetTester tester) async {
       final GlobalKey key1 = GlobalKey(debugLabel: '1');

packages/flutter/test/widgets/navigator_test.dart

@@ -1489,29 +1489,34 @@ void main() {
         return result;
       },
     ));
-    expect(log, <String>['building page 1 - false']);
+    final List<String> expected = <String>['building page 1 - false'];
+    expect(log, expected);
     key.currentState!.pushReplacement(PageRouteBuilder<int>(
       pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
         log.add('building page 2 - ${ModalRoute.of(context)!.canPop}');
         return const Placeholder();
       },
     ));
-    expect(log, <String>['building page 1 - false']);
+    expect(log, expected);
     await tester.pump();
-    expect(log, <String>['building page 1 - false', 'building page 2 - false']);
+    expected.add('building page 2 - false');
+    expected.add('building page 1 - false'); // page 1 is rebuilt again because isCurrent changed.
+    expect(log, expected);
     await tester.pump(const Duration(milliseconds: 150));
-    expect(log, <String>['building page 1 - false', 'building page 2 - false']);
+    expect(log, expected);
     key.currentState!.pushReplacement(PageRouteBuilder<int>(
       pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
         log.add('building page 3 - ${ModalRoute.of(context)!.canPop}');
         return const Placeholder();
       },
     ));
-    expect(log, <String>['building page 1 - false', 'building page 2 - false']);
+    expect(log, expected);
     await tester.pump();
-    expect(log, <String>['building page 1 - false', 'building page 2 - false', 'building page 3 - false']);
+    expected.add('building page 3 - false');
+    expected.add('building page 2 - false'); // page 2 is rebuilt again because isCurrent changed.
+    expect(log, expected);
     await tester.pump(const Duration(milliseconds: 200));
-    expect(log, <String>['building page 1 - false', 'building page 2 - false', 'building page 3 - false']);
+    expect(log, expected);
   });
 
   testWidgetsWithLeakTracking('route semantics', (WidgetTester tester) async {