[go_router] Add GoRouter.maybeOf (flutter#3216)

* feat: Add GoRouter.maybeOf

* docs: Update the version number

* test: Add tests on GoRouter.of and GoRouter.maybeOf

Author: ValentinVignal

packages/go_router/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 6.1.0
+
+- Adds `GoRouter.maybeOf` to get the closest `GoRouter` from the context, if there is any.
+
 ## 6.0.10
 
 - Adds helpers for go_router_builder for ShellRoute support

packages/go_router/lib/src/router.dart

@@ -301,6 +301,13 @@ class GoRouter extends ChangeNotifier implements RouterConfig<RouteMatchList> {
     return inherited!.goRouter;
   }
 
+  /// The current GoRouter in the widget tree, if any.
+  static GoRouter? maybeOf(BuildContext context) {
+    final InheritedGoRouter? inherited =
+        context.dependOnInheritedWidgetOfExactType<InheritedGoRouter>();
+    return inherited?.goRouter;
+  }
+
   @override
   void dispose() {
     _routeInformationProvider.dispose();

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: 6.0.10
+version: 6.1.0
 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

@@ -3275,6 +3275,68 @@ void main() {
       });
     });
   });
+
+  group('of', () {
+    testWidgets(
+      'It should return the go router instance of the widget tree',
+      (WidgetTester tester) async {
+        const Key key = Key('key');
+        final List<RouteBase> routes = <RouteBase>[
+          GoRoute(
+            path: '/',
+            builder: (_, __) => const SizedBox(key: key),
+          ),
+        ];
+
+        final GoRouter router = await createRouter(routes, tester);
+        final Element context = tester.element(find.byKey(key));
+        final GoRouter foundRouter = GoRouter.of(context);
+        expect(foundRouter, router);
+      },
+    );
+
+    testWidgets(
+      'It should throw if there is no go router in the widget tree',
+      (WidgetTester tester) async {
+        const Key key = Key('key');
+        await tester.pumpWidget(const SizedBox(key: key));
+
+        final Element context = tester.element(find.byKey(key));
+        expect(() => GoRouter.of(context), throwsA(anything));
+      },
+    );
+  });
+
+  group('maybeOf', () {
+    testWidgets(
+      'It should return the go router instance of the widget tree',
+      (WidgetTester tester) async {
+        const Key key = Key('key');
+        final List<RouteBase> routes = <RouteBase>[
+          GoRoute(
+            path: '/',
+            builder: (_, __) => const SizedBox(key: key),
+          ),
+        ];
+
+        final GoRouter router = await createRouter(routes, tester);
+        final Element context = tester.element(find.byKey(key));
+        final GoRouter? foundRouter = GoRouter.maybeOf(context);
+        expect(foundRouter, router);
+      },
+    );
+
+    testWidgets(
+      'It should return null if there is no go router in the widget tree',
+      (WidgetTester tester) async {
+        const Key key = Key('key');
+        await tester.pumpWidget(const SizedBox(key: key));
+
+        final Element context = tester.element(find.byKey(key));
+        expect(GoRouter.maybeOf(context), isNull);
+      },
+    );
+  });
 }
 
 /// This allows a value of type T or T? to be treated as a value of type T?.