[go_router] add current state getter (#7651)

Adds a current state getter that returns `GoRouterState`.

I've no idea if this is correct but the added tests seem to be passing. Rebuilding the state may be expensive too ?

Fix: flutter/flutter#129833 
fixes flutter/flutter#148215

packages/go_router/CHANGELOG.md

@@ -1,6 +1,10 @@
+## 14.4.0
+
+- Adds current state getter on `GoRouter` that returns the current `GoRouterState`.
+
 ## 14.3.0
 
-- Added missing implementation for the routerNeglect parameter in GoRouter.
+- Adds missing implementation for the routerNeglect parameter in GoRouter.
 
 ## 14.2.9
 

packages/go_router/lib/src/delegate.dart

@@ -13,6 +13,7 @@ import 'configuration.dart';
 import 'match.dart';
 import 'misc/errors.dart';
 import 'route.dart';
+import 'state.dart';
 
 /// GoRouter implementation of [RouterDelegate].
 class GoRouterDelegate extends RouterDelegate<RouteMatchList>
@@ -169,6 +170,11 @@ class GoRouterDelegate extends RouterDelegate<RouteMatchList>
     }());
   }
 
+  /// The top [GoRouterState], the state of the route that was
+  /// last used in either [GoRouter.go] or [GoRouter.push].
+  GoRouterState? get state => currentConfiguration.last
+      .buildState(_configuration, currentConfiguration);
+
   /// For use by the Router architecture as part of the RouterDelegate.
   GlobalKey<NavigatorState> get navigatorKey => _configuration.navigatorKey;
 

packages/go_router/lib/src/router.dart

@@ -255,6 +255,14 @@ class GoRouter implements RouterConfig<RouteMatchList> {
     }());
   }
 
+  /// The top [GoRouterState], the state of the route that was
+  /// last used in either [GoRouter.go] or [GoRouter.push].
+  ///
+  /// Accessing this property via GoRouter.of(context).state will not
+  /// cause rebuild if the state has changed, consider using
+  /// GoRouterState.of(context) instead.
+  GoRouterState? get state => routerDelegate.state;
+
   /// Whether the imperative API affects browser URL bar.
   ///
   /// The Imperative APIs refer to [push], [pushReplacement], or [replace].

packages/go_router/pubspec.yaml

@@ -1,7 +1,7 @@
 name: go_router
 description: A declarative router for Flutter based on Navigation 2 supporting
   deep linking, data-driven routes and more
-version: 14.3.0
+version: 14.4.0
 repository: https://github.com/flutter/packages/tree/main/packages/go_router
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+go_router%22
 

packages/go_router/test/go_router_test.dart

@@ -5474,6 +5474,78 @@ void main() {
     );
   });
 
+  testWidgets(
+      'should return the current GoRouterState when router.currentState is called',
+      (WidgetTester tester) async {
+    final List<RouteBase> routes = <RouteBase>[
+      GoRoute(
+          name: 'home',
+          path: '/',
+          builder: (BuildContext context, GoRouterState state) =>
+              const HomeScreen()),
+      GoRoute(
+          name: 'books',
+          path: '/books',
+          builder: (BuildContext context, GoRouterState state) =>
+              const Text('books')),
+      GoRoute(
+          name: 'boats',
+          path: '/boats',
+          builder: (BuildContext context, GoRouterState state) =>
+              const Text('boats')),
+      ShellRoute(
+        builder: (BuildContext context, GoRouterState state, Widget child) =>
+            child,
+        routes: <RouteBase>[
+          GoRoute(
+            name: 'tulips',
+            path: '/tulips',
+            builder: (BuildContext context, GoRouterState state) =>
+                const Text('tulips'),
+          ),
+        ],
+      )
+    ];
+
+    final GoRouter router = await createRouter(routes, tester);
+    await tester.pumpAndSettle();
+
+    GoRouterState? state = router.state;
+    expect(state?.name, 'home');
+    expect(state?.fullPath, '/');
+
+    router.go('/books');
+    await tester.pumpAndSettle();
+    state = router.state;
+    expect(state?.name, 'books');
+    expect(state?.fullPath, '/books');
+
+    router.push('/boats');
+    await tester.pumpAndSettle();
+    state = router.state;
+    expect(state?.name, 'boats');
+    expect(state?.fullPath, '/boats');
+
+    router.pop();
+    await tester.pumpAndSettle();
+    state = router.state;
+    expect(state?.name, 'books');
+    expect(state?.fullPath, '/books');
+
+    router.go('/tulips');
+    await tester.pumpAndSettle();
+    state = router.state;
+    expect(state?.name, 'tulips');
+    expect(state?.fullPath, '/tulips');
+
+    router.go('/books');
+    router.push('/tulips');
+    await tester.pumpAndSettle();
+    state = router.state;
+    expect(state?.name, 'tulips');
+    expect(state?.fullPath, '/tulips');
+  });
+
   testWidgets('should allow route paths without leading /',
       (WidgetTester tester) async {
     final List<GoRoute> routes = <GoRoute>[