fix changinternalstate crash when remove local history entry in final… (#52561)

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

@@ -6,6 +6,7 @@ import 'dart:async';
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
+import 'package:flutter/scheduler.dart';
 
 import 'basic.dart';
 import 'focus_manager.dart';
@@ -606,9 +607,19 @@ mixin LocalHistoryRoute<T> on Route<T> {
     _localHistory.remove(entry);
     entry._owner = null;
     entry._notifyRemoved();
-    if (_localHistory.isEmpty)
+    if (_localHistory.isEmpty) {
+      if (SchedulerBinding.instance.schedulerPhase == SchedulerPhase.persistentCallbacks) {
+        // The local history might be removed as a result of disposing inactive
+        // elements during finalizeTree. The state is locked at this moment, and
+        // we can only notify state has changed in the next frame.
+        SchedulerBinding.instance.addPostFrameCallback((Duration duration) {
+          changedInternalState();
+        });
+      } else {
         changedInternalState();
       }
+    }
+  }
 
   @override
   Future<RoutePopDisposition> willPop() async {

packages/flutter/test/widgets/routes_test.dart

@@ -1294,6 +1294,28 @@ void main() {
       // It should refocus page one after pops.
       expect(focusNodeOnPageOne.hasFocus, isTrue);
     });
+
+    testWidgets('child with local history can be disposed', (WidgetTester tester) async {
+      // Regression test: https://github.com/flutter/flutter/issues/52478
+      await tester.pumpWidget(MaterialApp(
+        home: WidgetWithLocalHistory(),
+      ));
+
+      final WidgetWithLocalHistoryState state = tester.state(find.byType(WidgetWithLocalHistory));
+      state.addLocalHistory();
+      // Waits for modal route to update its internal state;
+      await tester.pump();
+
+      // Pumps a new widget to dispose WidgetWithLocalHistory. This should cause
+      // it to remove the local history entry from modal route during
+      // finalizeTree.
+      await tester.pumpWidget(const MaterialApp(
+        home: Text('dummy'),
+      ));
+      // Waits for modal route to update its internal state;
+      await tester.pump();
+      expect(tester.takeException(), null);
+    });
   });
 }
 
@@ -1390,3 +1412,29 @@ class _TestDialogRouteWithCustomBarrierCurve<T> extends PopupRoute<T> {
     );
   }
 }
+
+class WidgetWithLocalHistory extends StatefulWidget {
+  @override
+  WidgetWithLocalHistoryState createState() => WidgetWithLocalHistoryState();
+}
+
+class WidgetWithLocalHistoryState extends State<WidgetWithLocalHistory> {
+  LocalHistoryEntry _localHistory;
+
+  void addLocalHistory() {
+    final ModalRoute<dynamic> route = ModalRoute.of(context);
+    _localHistory = LocalHistoryEntry();
+    route.addLocalHistoryEntry(_localHistory);
+  }
+
+  @override
+  void dispose() {
+    super.dispose();
+    _localHistory.remove();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return const Text('dummy');
+  }
+}