Ignore unmounted parent when _debugVerifyGlobalKeyReservation for GlobalKey check (#62323)

* Ignore unmounted parent when _debugVerifyGlobalKeyReservation (#62055)

* Ignore unmounted parent when _debugVerifyGlobalKeyReservation (#62055)

* Ignore unmounted parent when _debugVerifyGlobalKeyReservation (#62055)

* Ignore unmounted parent when _debugVerifyGlobalKeyReservation (#62055)

* Ignore unmounted parent when _debugVerifyGlobalKeyReservation (#62055)

* Ignore unmounted parent when _debugVerifyGlobalKeyReservation (#62055)

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

@@ -194,8 +194,8 @@ abstract class GlobalKey<T extends State<StatefulWidget>> extends Key {
     assert(() {
       final Map<GlobalKey, Element> keyToParent = <GlobalKey, Element>{};
       _debugReservations.forEach((Element parent, Map<Element, GlobalKey> childToKey) {
-        // We ignore parent that are detached.
-        if (parent.renderObject?.attached == false)
+        // We ignore parent that are unmounted or detached.
+        if (parent._debugLifecycleState == _ElementLifecycle.defunct || parent.renderObject?.attached == false)
           return;
         childToKey.forEach((Element child, GlobalKey key) {
           // If parent = null, the node is deactivated by its parent and is

packages/flutter/test/widgets/framework_test.dart

@@ -4,6 +4,7 @@
 
 // @dart = 2.8
 
+import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
@@ -1061,6 +1062,52 @@ void main() {
     element.createChild(0, after: null);
   });
 
+  testWidgets('GlobalKey - re-attach child to new parents, and the old parent is deactivated(unmounted)', (WidgetTester tester) async {
+    // This is a regression test for https://github.com/flutter/flutter/issues/62055
+    const Key key1 = GlobalObjectKey('key1');
+    const Key key2 = GlobalObjectKey('key2');
+    StateSetter setState;
+    int tabBarViewCnt = 2;
+    TabController tabController = TabController(length: tabBarViewCnt, vsync: const TestVSync(),);
+
+    await tester.pumpWidget(Directionality(
+      textDirection: TextDirection.ltr,
+      child: StatefulBuilder(
+        builder: (BuildContext context, StateSetter setter) {
+          setState = setter;
+          return TabBarView(
+            controller: tabController,
+            children: <Widget>[
+              if (tabBarViewCnt > 0) const Text('key1', key: key1,),
+              if (tabBarViewCnt > 1) const Text('key2', key: key2,),
+            ],
+          );
+        },
+      ),
+    ));
+
+    expect(tabController.index, 0);
+
+    // switch tabs 0 -> 1
+    setState((){
+      tabController.index = 1;
+    });
+
+    await tester.pump(const Duration(seconds: 1)); // finish the animation
+
+    expect(tabController.index, 1);
+
+    // rebuild TabBarView that only have the 1st page with GlobalKey 'key1'
+    setState((){
+      tabBarViewCnt = 1;
+      tabController = TabController(length: tabBarViewCnt, vsync: const TestVSync(),);
+    });
+
+    await tester.pump(const Duration(seconds: 1)); // finish the animation
+
+    expect(tabController.index, 0);
+  });
+
   testWidgets('Defunct setState throws exception', (WidgetTester tester) async {
     StateSetter setState;