Add restorationId to Material/CupertinoPage (#78450)

packages/flutter/lib/src/cupertino/route.dart

@@ -401,10 +401,11 @@ class CupertinoPage<T> extends Page<T> {
     LocalKey? key,
     String? name,
     Object? arguments,
+    String? restorationId,
   }) : assert(child != null),
        assert(maintainState != null),
        assert(fullscreenDialog != null),
-       super(key: key, name: name, arguments: arguments);
+       super(key: key, name: name, arguments: arguments, restorationId: restorationId);
 
   /// The content to be shown in the [Route] created by this page.
   final Widget child;

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

@@ -156,10 +156,11 @@ class MaterialPage<T> extends Page<T> {
     LocalKey? key,
     String? name,
     Object? arguments,
+    String? restorationId,
   }) : assert(child != null),
        assert(maintainState != null),
        assert(fullscreenDialog != null),
-       super(key: key, name: name, arguments: arguments);
+       super(key: key, name: name, arguments: arguments, restorationId: restorationId);
 
   /// The content to be shown in the [Route] created by this page.
   final Widget child;

packages/flutter/test/cupertino/page_test.dart

@@ -475,6 +475,68 @@ void main() {
     expect(find.text('subpage'), findsOneWidget);
     expect(find.text('home'), findsOneWidget);
   });
+
+  testWidgets('CupertinoPage restores its state', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      RootRestorationScope(
+        restorationId: 'root',
+        child: MediaQuery(
+          data: const MediaQueryData(),
+          child: Directionality(
+            textDirection: TextDirection.ltr,
+            child: Navigator(
+              onPopPage: (Route<dynamic> route, dynamic result) { return false; },
+              pages: const <Page<Object?>>[
+                CupertinoPage<void>(
+                  restorationId: 'p1',
+                  child: TestRestorableWidget(restorationId: 'p1'),
+                ),
+              ],
+              restorationScopeId: 'nav',
+              onGenerateRoute: (RouteSettings settings) {
+                return CupertinoPageRoute<void>(
+                  settings: settings,
+                  builder: (BuildContext context) {
+                    return TestRestorableWidget(restorationId: settings.name!);
+                  },
+                );
+              },
+            ),
+          ),
+        ),
+      ),
+    );
+
+    expect(find.text('p1'), findsOneWidget);
+    expect(find.text('count: 0'), findsOneWidget);
+
+    await tester.tap(find.text('increment'));
+    await tester.pump();
+    expect(find.text('count: 1'), findsOneWidget);
+
+    tester.state<NavigatorState>(find.byType(Navigator)).restorablePushNamed('p2');
+    await tester.pumpAndSettle();
+
+    expect(find.text('p1'), findsNothing);
+    expect(find.text('p2'), findsOneWidget);
+
+    await tester.tap(find.text('increment'));
+    await tester.pump();
+    await tester.tap(find.text('increment'));
+    await tester.pump();
+    expect(find.text('count: 2'), findsOneWidget);
+
+    await tester.restartAndRestore();
+
+    expect(find.text('p2'), findsOneWidget);
+    expect(find.text('count: 2'), findsOneWidget);
+
+    tester.state<NavigatorState>(find.byType(Navigator)).pop();
+    await tester.pumpAndSettle();
+
+    expect(find.text('p1'), findsOneWidget);
+    expect(find.text('count: 1'), findsOneWidget);
+  });
 }
 
 class RtlOverrideWidgetsDelegate extends LocalizationsDelegate<WidgetsLocalizations> {
@@ -527,3 +589,42 @@ class _KeepsStateTestWidgetState extends State<KeepsStateTestWidget> {
     );
   }
 }
+
+class TestRestorableWidget extends StatefulWidget {
+  const TestRestorableWidget({Key? key, required this.restorationId}) : super(key: key);
+
+  final String restorationId;
+
+  @override
+  State<StatefulWidget> createState() => _TestRestorableWidgetState();
+}
+
+class _TestRestorableWidgetState extends State<TestRestorableWidget> with RestorationMixin {
+  @override
+  String? get restorationId => widget.restorationId;
+
+  final RestorableInt counter = RestorableInt(0);
+
+  @override
+  void restoreState(RestorationBucket? oldBucket, bool initialRestore) {
+    registerForRestoration(counter, 'counter');
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      children: <Widget>[
+        Text(widget.restorationId),
+        Text('count: ${counter.value}'),
+        CupertinoButton(
+          onPressed: () {
+            setState(() {
+              counter.value++;
+            });
+          },
+          child: const Text('increment'),
+        ),
+      ],
+    );
+  }
+}

packages/flutter/test/material/page_test.dart

@@ -913,6 +913,65 @@ void main() {
     expect(find.text('subpage'), findsOneWidget);
     expect(find.text('home'), findsOneWidget);
   });
+
+  testWidgets('MaterialPage restores its state', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      RootRestorationScope(
+        restorationId: 'root',
+        child: Directionality(
+          textDirection: TextDirection.ltr,
+          child: Navigator(
+            onPopPage: (Route<dynamic> route, dynamic result) { return false; },
+            pages: const <Page<Object?>>[
+              MaterialPage<void>(
+                restorationId: 'p1',
+                child: TestRestorableWidget(restorationId: 'p1'),
+              ),
+            ],
+            restorationScopeId: 'nav',
+            onGenerateRoute: (RouteSettings settings) {
+              return MaterialPageRoute<void>(
+                settings: settings,
+                builder: (BuildContext context) {
+                  return TestRestorableWidget(restorationId: settings.name!);
+                },
+              );
+            },
+          ),
+        ),
+      ),
+    );
+
+    expect(find.text('p1'), findsOneWidget);
+    expect(find.text('count: 0'), findsOneWidget);
+
+    await tester.tap(find.text('increment'));
+    await tester.pump();
+    expect(find.text('count: 1'), findsOneWidget);
+
+    tester.state<NavigatorState>(find.byType(Navigator)).restorablePushNamed('p2');
+    await tester.pumpAndSettle();
+
+    expect(find.text('p1'), findsNothing);
+    expect(find.text('p2'), findsOneWidget);
+
+    await tester.tap(find.text('increment'));
+    await tester.pump();
+    await tester.tap(find.text('increment'));
+    await tester.pump();
+    expect(find.text('count: 2'), findsOneWidget);
+
+    await tester.restartAndRestore();
+
+    expect(find.text('p2'), findsOneWidget);
+    expect(find.text('count: 2'), findsOneWidget);
+
+    tester.state<NavigatorState>(find.byType(Navigator)).pop();
+    await tester.pumpAndSettle();
+
+    expect(find.text('p1'), findsOneWidget);
+    expect(find.text('count: 1'), findsOneWidget);
+  });
 }
 
 class TransitionDetector extends DefaultTransitionDelegate<void> {
@@ -993,3 +1052,42 @@ class _KeepsStateTestWidgetState extends State<KeepsStateTestWidget> {
     );
   }
 }
+
+class TestRestorableWidget extends StatefulWidget {
+  const TestRestorableWidget({Key? key, required this.restorationId}) : super(key: key);
+
+  final String restorationId;
+
+  @override
+  State<StatefulWidget> createState() => _TestRestorableWidgetState();
+}
+
+class _TestRestorableWidgetState extends State<TestRestorableWidget> with RestorationMixin {
+  @override
+  String? get restorationId => widget.restorationId;
+
+  final RestorableInt counter = RestorableInt(0);
+
+  @override
+  void restoreState(RestorationBucket? oldBucket, bool initialRestore) {
+    registerForRestoration(counter, 'counter');
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      children: <Widget>[
+        Text(widget.restorationId),
+        Text('count: ${counter.value}'),
+        ElevatedButton(
+          onPressed: () {
+            setState(() {
+              counter.value++;
+            });
+          },
+          child: const Text('increment'),
+        ),
+      ],
+    );
+  }
+}