[go_router] fix onExit ignored for GoRoute nested inside ShellRoute (#11853)

`onExit` was silently ignored when the route was nested inside a ShellRoute + added test for async and sync pop for this specific case
Attempt to fix flutter/flutter#137829 flutter/flutter#137829

*List which issues are fixed by this PR. You must list at least one issue.*

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Author: qiqetes

packages/go_router/lib/src/delegate.dart

@@ -137,7 +137,13 @@ class GoRouterDelegate extends RouterDelegate<RouteMatchList> with ChangeNotifie
       assert(!popped);
       return popped;
     }
-    final RouteBase routeBase = match.route;
+
+    var leafMatch = match;
+    while (leafMatch is ShellRouteMatch) {
+      leafMatch = leafMatch.matches.last;
+    }
+
+    final RouteBase routeBase = leafMatch.route;
     if (routeBase is! GoRoute || routeBase.onExit == null) {
       route.didPop(result);
       _completeRouteMatch(result, match);
@@ -150,7 +156,7 @@ class GoRouterDelegate extends RouterDelegate<RouteMatchList> with ChangeNotifie
     scheduleMicrotask(() async {
       final bool onExitResult = await routeBase.onExit!(
         navigatorKey.currentContext!,
-        match.buildState(_configuration, currentConfiguration),
+        leafMatch.buildState(_configuration, currentConfiguration),
       );
       if (onExitResult) {
         _completeRouteMatch(result, match);

packages/go_router/pending_changelogs/change_2026_06_07_1780787180781.yaml

@@ -0,0 +1,3 @@
+changelog: |
+  - Fixes onExit ignored for GoRoute nested inside ShellRoute
+version: patch

packages/go_router/test/on_exit_test.dart

@@ -528,4 +528,82 @@ void main() {
     expect(find.byKey(detailKey), findsOneWidget);
     expect(find.byKey(homeKey), findsNothing);
   });
+
+  // Regression test for https://github.com/flutter/flutter/issues/137829
+  testWidgets('back button works synchronously with ShellRoute', (WidgetTester tester) async {
+    var allow = false;
+    final home = UniqueKey();
+    final page = UniqueKey();
+    final routes = <RouteBase>[
+      GoRoute(
+        path: '/',
+        builder: (_, _) => DummyScreen(key: home),
+        routes: <RouteBase>[
+          ShellRoute(
+            builder: (_, _, Widget child) => child,
+            routes: <RouteBase>[
+              GoRoute(
+                path: 'page',
+                builder: (_, _) => DummyScreen(key: page),
+                onExit: (BuildContext context, GoRouterState state) => allow,
+              ),
+            ],
+          ),
+        ],
+      ),
+    ];
+
+    final GoRouter router = await createRouter(routes, tester, initialLocation: '/page');
+    expect(find.byKey(page), findsOneWidget);
+
+    router.pop();
+    await tester.pumpAndSettle();
+    expect(find.byKey(page), findsOneWidget);
+
+    allow = true;
+    router.pop();
+    await tester.pumpAndSettle();
+    expect(find.byKey(home), findsOneWidget);
+  });
+
+  // Regression test for https://github.com/flutter/flutter/issues/137829
+  testWidgets('back button works asynchronously with ShellRoute', (WidgetTester tester) async {
+    var allow = Completer<bool>();
+    final home = UniqueKey();
+    final page = UniqueKey();
+    final routes = <RouteBase>[
+      GoRoute(
+        path: '/',
+        builder: (_, _) => DummyScreen(key: home),
+        routes: <RouteBase>[
+          ShellRoute(
+            builder: (_, _, Widget child) => child,
+            routes: <RouteBase>[
+              GoRoute(
+                path: 'page',
+                builder: (_, _) => DummyScreen(key: page),
+                onExit: (BuildContext context, GoRouterState state) async => allow.future,
+              ),
+            ],
+          ),
+        ],
+      ),
+    ];
+
+    final GoRouter router = await createRouter(routes, tester, initialLocation: '/page');
+    expect(find.byKey(page), findsOneWidget);
+
+    router.pop();
+    await tester.pumpAndSettle();
+    allow.complete(false);
+    await tester.pumpAndSettle();
+    expect(find.byKey(page), findsOneWidget);
+
+    allow = Completer<bool>();
+    router.pop();
+    await tester.pumpAndSettle();
+    allow.complete(true);
+    await tester.pumpAndSettle();
+    expect(find.byKey(home), findsOneWidget);
+  });
 }