[go_router] Fixes "Bad state: Future already completed" when a route with onExit is popped twice

packages/go_router/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 17.5.1
+
+- Fixes a `StateError` ("Bad state: Future already completed") when a route with an `onExit` callback is popped twice before the navigator rebuilds.
+
 ## 17.5.0
 
 - Adds route `metadata` support, including inheritance and override behavior with exposure on `GoRouterState`.

packages/go_router/lib/src/match.dart

@@ -458,7 +458,15 @@ class ImperativeRouteMatch extends RouteMatch {
 
   /// Called when the corresponding [Route] associated with this route match is
   /// completed.
+  ///
+  /// A route match can be completed more than once when the same route is
+  /// popped again before the navigator has rebuilt; for example, two back
+  /// events in quick succession while an `onExit` callback defers the pop to a
+  /// microtask. Only the first completion is reported; later ones are ignored.
   void complete([dynamic value]) {
+    if (completer.isCompleted) {
+      return;
+    }
     completer.complete(value);
   }
 

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: 17.5.0
+version: 17.5.1
 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/on_exit_test.dart

@@ -529,6 +529,45 @@ void main() {
     expect(find.byKey(homeKey), findsNothing);
   });
 
+  // Regression test for https://github.com/flutter/flutter/issues/191280
+  testWidgets('popping a route with onExit twice before the navigator rebuilds does not throw', (
+    WidgetTester tester,
+  ) async {
+    final homeKey = UniqueKey();
+    final detailKey = UniqueKey();
+
+    final GoRouter router = await createRouter(
+      <RouteBase>[
+        GoRoute(
+          path: '/',
+          builder: (_, _) => DummyScreen(key: homeKey),
+          routes: <RouteBase>[
+            GoRoute(
+              path: 'detail',
+              onExit: (_, _) => true,
+              builder: (_, _) => DummyScreen(key: detailKey),
+            ),
+          ],
+        ),
+      ],
+      tester,
+    );
+
+    final Future<Object?> pushFuture = router.push('/detail');
+    await tester.pumpAndSettle();
+    expect(find.byKey(detailKey), findsOneWidget);
+
+    // Two back events arrive before the deferred pop is applied — e.g. a user
+    // tapping the back button twice in quick succession.
+    router.pop('first');
+    router.pop('second');
+    await tester.pumpAndSettle();
+
+    expect(tester.takeException(), isNull);
+    expect(find.byKey(homeKey), findsOneWidget);
+    expect(await pushFuture, 'first');
+  });
+
   // Regression test for https://github.com/flutter/flutter/issues/137829
   testWidgets('back button works synchronously with ShellRoute', (WidgetTester tester) async {
     var allow = false;