Can traverse if current focused node skips traversal (#130812)

Currently if the focus is on a focusnode that `skipTraversal = true`, the tab won't be able to traverse focus out of the node.

this pr fixes it

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

@@ -352,7 +352,7 @@ abstract class FocusTraversalPolicy with Diagnosticable {
   @protected
   Iterable<FocusNode> sortDescendants(Iterable<FocusNode> descendants, FocusNode currentNode);
 
-  Map<FocusNode?, _FocusTraversalGroupInfo> _findGroups(FocusScopeNode scope, _FocusTraversalGroupNode? scopeGroupNode) {
+  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) {
@@ -374,7 +374,10 @@ abstract class FocusTraversalPolicy with Diagnosticable {
       }
       // Skip non-focusable and non-traversable nodes in the same way that
       // FocusScopeNode.traversalDescendants would.
-      if (node.canRequestFocus && !node.skipTraversal) {
+      //
+      // Current focused node needs to be in the group so that the caller can
+      // find the next traversable node from the current focused node.
+      if (node == currentNode || (node.canRequestFocus && !node.skipTraversal)) {
         groups[groupNode] ??= _FocusTraversalGroupInfo(groupNode, members: <FocusNode>[], defaultPolicy: defaultPolicy);
         assert(!groups[groupNode]!.members.contains(node));
         groups[groupNode]!.members.add(node);
@@ -388,7 +391,7 @@ abstract class FocusTraversalPolicy with Diagnosticable {
   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);
+    final Map<FocusNode?, _FocusTraversalGroupInfo> groups = _findGroups(scope, scopeGroupNode, currentNode);
 
     // Sort the member lists using the individual policy sorts.
     for (final FocusNode? key in groups.keys) {
@@ -397,6 +400,7 @@ abstract class FocusTraversalPolicy with Diagnosticable {
       groups[key]!.members.addAll(sortedMembers);
     }
 
+
     // Traverse the group tree, adding the children of members in the order they
     // appear in the member lists.
     final List<FocusNode> sortedDescendants = <FocusNode>[];
@@ -421,17 +425,29 @@ abstract class FocusTraversalPolicy with Diagnosticable {
     // They were left in above because they were needed to find their members
     // during sorting.
     sortedDescendants.removeWhere((FocusNode node) {
-      return !node.canRequestFocus || node.skipTraversal;
+      return node != currentNode && (!node.canRequestFocus || node.skipTraversal);
     });
 
     // Sanity check to make sure that the algorithm above doesn't diverge from
     // the one in FocusScopeNode.traversalDescendants in terms of which nodes it
     // finds.
+    assert((){
+      final Set<FocusNode> difference = sortedDescendants.toSet().difference(scope.traversalDescendants.toSet());
+      if (currentNode.skipTraversal) {
         assert(
-      sortedDescendants.length <= scope.traversalDescendants.length && sortedDescendants.toSet().difference(scope.traversalDescendants.toSet()).isEmpty,
+         difference.length == 1 && difference.contains(currentNode),
          'Sorted descendants contains different nodes than FocusScopeNode.traversalDescendants would. '
-      'These are the different nodes: ${sortedDescendants.toSet().difference(scope.traversalDescendants.toSet())}',
+         'These are the different nodes: ${difference.where((FocusNode node) => node != currentNode)}',
         );
+        return true;
+      }
+      assert(
+        difference.isEmpty,
+        'Sorted descendants contains different nodes than FocusScopeNode.traversalDescendants would. '
+        'These are the different nodes: $difference',
+      );
+      return true;
+    }());
     return sortedDescendants;
   }
 
@@ -453,7 +469,7 @@ abstract class FocusTraversalPolicy with Diagnosticable {
   bool _moveFocus(FocusNode currentNode, {required bool forward}) {
     final FocusScopeNode nearestScope = currentNode.nearestScope!;
     invalidateScopeData(nearestScope);
-    final FocusNode? focusedChild = nearestScope.focusedChild;
+    FocusNode? focusedChild = nearestScope.focusedChild;
     if (focusedChild == null) {
       final FocusNode? firstFocus = forward ? findFirstFocus(currentNode) : findLastFocus(currentNode);
       if (firstFocus != null) {
@@ -464,8 +480,11 @@ abstract class FocusTraversalPolicy with Diagnosticable {
         return true;
       }
     }
-    final List<FocusNode> sortedNodes = _sortAllDescendants(nearestScope, currentNode);
-    if (sortedNodes.isEmpty) {
+    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;
@@ -473,7 +492,7 @@ abstract class FocusTraversalPolicy with Diagnosticable {
     if (forward && focusedChild == sortedNodes.last) {
       switch (nearestScope.traversalEdgeBehavior) {
         case TraversalEdgeBehavior.leaveFlutterView:
-          focusedChild!.unfocus();
+          focusedChild.unfocus();
           return false;
         case TraversalEdgeBehavior.closedLoop:
           requestFocusCallback(sortedNodes.first, alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtEnd);
@@ -483,7 +502,7 @@ abstract class FocusTraversalPolicy with Diagnosticable {
     if (!forward && focusedChild == sortedNodes.first) {
       switch (nearestScope.traversalEdgeBehavior) {
         case TraversalEdgeBehavior.leaveFlutterView:
-          focusedChild!.unfocus();
+          focusedChild.unfocus();
           return false;
         case TraversalEdgeBehavior.closedLoop:
           requestFocusCallback(sortedNodes.last, alignmentPolicy: ScrollPositionAlignmentPolicy.keepVisibleAtStart);

packages/flutter/test/material/icon_button_test.dart

@@ -812,7 +812,7 @@ void main() {
     expect(focusNode1.hasPrimaryFocus, isTrue);
     expect(focusNode2.hasPrimaryFocus, isFalse);
 
-    expect(focusNode1.nextFocus(), isTrue);
+    expect(focusNode1.nextFocus(), isFalse);
     await tester.pump();
 
     expect(focusNode1.hasPrimaryFocus, isTrue);

packages/flutter/test/material/input_chip_test.dart

@@ -271,7 +271,7 @@ void main() {
     expect(focusNode1.hasPrimaryFocus, isTrue);
     expect(focusNode2.hasPrimaryFocus, isFalse);
 
-    expect(focusNode1.nextFocus(), isTrue);
+    expect(focusNode1.nextFocus(), isFalse);
 
     await tester.pump();
     expect(focusNode1.hasPrimaryFocus, isTrue);

packages/flutter/test/material/raw_material_button_test.dart

@@ -414,7 +414,7 @@ void main() {
     expect(focusNode1.hasPrimaryFocus, isTrue);
     expect(focusNode2.hasPrimaryFocus, isFalse);
 
-    expect(focusNode1.nextFocus(), isTrue);
+    expect(focusNode1.nextFocus(), isFalse);
     await tester.pump();
 
     expect(focusNode1.hasPrimaryFocus, isTrue);

packages/flutter/test/material/text_field_test.dart

@@ -6690,7 +6690,7 @@ void main() {
     expect(focusNode1.hasPrimaryFocus, isTrue);
     expect(focusNode2.hasPrimaryFocus, isFalse);
 
-    expect(focusNode1.nextFocus(), isTrue);
+    expect(focusNode1.nextFocus(), isFalse);
     await tester.pump();
 
     expect(focusNode1.hasPrimaryFocus, isTrue);

packages/flutter/test/widgets/actions_test.dart

@@ -908,6 +908,7 @@ void main() {
         await tester.pumpWidget(
           MaterialApp(
             home: FocusableActionDetector(
+              focusNode: FocusNode(skipTraversal: true),
               child: Column(
                 children: <Widget>[
                   ElevatedButton(
@@ -938,6 +939,7 @@ void main() {
         await tester.pumpWidget(
           MaterialApp(
             home: FocusableActionDetector(
+              focusNode: FocusNode(skipTraversal: true),
               descendantsAreTraversable: false,
               child: Column(
                 children: <Widget>[

packages/flutter/test/widgets/focus_traversal_test.dart

@@ -2090,6 +2090,61 @@ void main() {
       expect(Focus.of(upperLeftKey.currentContext!).hasPrimaryFocus, isTrue);
     }, skip: isBrowser, variant: KeySimulatorTransitModeVariant.all()); // https://github.com/flutter/flutter/issues/35347
 
+    testWidgets('Focus traversal actions works when current focus skip traversal', (WidgetTester tester) async {
+      final GlobalKey key1 = GlobalKey(debugLabel: 'key1');
+      final GlobalKey key2 = GlobalKey(debugLabel: 'key2');
+      final GlobalKey key3 = GlobalKey(debugLabel: 'key3');
+
+      await tester.pumpWidget(
+        WidgetsApp(
+          color: const Color(0xFFFFFFFF),
+          onGenerateRoute: (RouteSettings settings) {
+            return TestRoute(
+              child: Directionality(
+                textDirection: TextDirection.ltr,
+                child: FocusScope(
+                  debugLabel: 'scope',
+                  child: Column(
+                    children: <Widget>[
+                      Row(
+                        children: <Widget>[
+                          Focus(
+                            autofocus: true,
+                            skipTraversal: true,
+                            debugLabel: '1',
+                            child: SizedBox(width: 100, height: 100, key: key1),
+                          ),
+                          Focus(
+                            debugLabel: '2',
+                            child: SizedBox(width: 100, height: 100, key: key2),
+                          ),
+                          Focus(
+                            debugLabel: '3',
+                            child: SizedBox(width: 100, height: 100, key: key3),
+                          ),
+                        ],
+                      ),
+                    ],
+                  ),
+                ),
+              ),
+            );
+          },
+        ),
+      );
+
+      expect(Focus.of(key1.currentContext!).hasPrimaryFocus, isTrue);
+      await tester.sendKeyEvent(LogicalKeyboardKey.tab);
+      expect(Focus.of(key2.currentContext!).hasPrimaryFocus, isTrue);
+      await tester.sendKeyEvent(LogicalKeyboardKey.tab);
+      expect(Focus.of(key3.currentContext!).hasPrimaryFocus, isTrue);
+      await tester.sendKeyEvent(LogicalKeyboardKey.tab);
+      // Skips key 1 because it skips traversal.
+      expect(Focus.of(key2.currentContext!).hasPrimaryFocus, isTrue);
+      await tester.sendKeyEvent(LogicalKeyboardKey.tab);
+      expect(Focus.of(key3.currentContext!).hasPrimaryFocus, isTrue);
+    }, skip: isBrowser, variant: KeySimulatorTransitModeVariant.all()); // https://github.com/flutter/flutter/issues/35347
+
     testWidgets('Focus traversal inside a vertical scrollable scrolls to stay visible.', (WidgetTester tester) async {
       final List<int> items = List<int>.generate(11, (int index) => index).toList();
       final List<FocusNode> nodes = List<FocusNode>.generate(11, (int index) => FocusNode(debugLabel: 'Item ${index + 1}')).toList();