[go_router] Block.then(() => router.go(...)) navigation silently lost when triggered by refreshListenable

### What package does this bug report belong to?

go_router

### What target platforms are you seeing this bug on?

Web

### Have you already upgraded your packages?

Yes

### Dependency versions

<details><summary>pubspec.lock</summary>

```lock
# Generated by pub
# See https://dart.dev/tools/pub/glossary#lockfile
packages:
  async:
    dependency: transitive
    description:
      name: async
      sha256: "758e6d74e971c3e5aceb4110bfd6698efc7f501675bcfe0c775459a8140750eb"
      url: "https://pub.dev"
    source: hosted
    version: "2.13.0"
  boolean_selector:
    dependency: transitive
    description:
      name: boolean_selector
      sha256: "8aab1771e1243a5063b8b0ff68042d67334e3feab9e95b9490f9a6ebf73b42ea"
      url: "https://pub.dev"
    source: hosted
    version: "2.1.2"
  characters:
    dependency: transitive
    description:
      name: characters
      sha256: faf38497bda5ead2a8c7615f4f7939df04333478bf32e4173fcb06d428b5716b
      url: "https://pub.dev"
    source: hosted
    version: "1.4.1"
  clock:
    dependency: transitive
    description:
      name: clock
      sha256: fddb70d9b5277016c77a80201021d40a2247104d9f4aa7bab7157b7e3f05b84b
      url: "https://pub.dev"
    source: hosted
    version: "1.1.2"
  collection:
    dependency: transitive
    description:
      name: collection
      sha256: "2f5709ae4d3d59dd8f7cd309b4e023046b57d8a6c82130785d2b0e5868084e76"
      url: "https://pub.dev"
    source: hosted
    version: "1.19.1"
  fake_async:
    dependency: transitive
    description:
      name: fake_async
      sha256: "5368f224a74523e8d2e7399ea1638b37aecfca824a3cc4dfdf77bf1fa905ac44"
      url: "https://pub.dev"
    source: hosted
    version: "1.3.3"
  flutter:
    dependency: "direct main"
    description: flutter
    source: sdk
    version: "0.0.0"
  flutter_lints:
    dependency: "direct dev"
    description:
      name: flutter_lints
      sha256: "3105dc8492f6183fb076ccf1f351ac3d60564bff92e20bfc4af9cc1651f4e7e1"
      url: "https://pub.dev"
    source: hosted
    version: "6.0.0"
  flutter_test:
    dependency: "direct dev"
    description: flutter
    source: sdk
    version: "0.0.0"
  flutter_web_plugins:
    dependency: transitive
    description: flutter
    source: sdk
    version: "0.0.0"
  go_router:
    dependency: "direct main"
    description:
      name: go_router
      sha256: "7974313e217a7771557add6ff2238acb63f635317c35fa590d348fb238f00896"
      url: "https://pub.dev"
    source: hosted
    version: "17.1.0"
  leak_tracker:
    dependency: transitive
    description:
      name: leak_tracker
      sha256: "33e2e26bdd85a0112ec15400c8cbffea70d0f9c3407491f672a2fad47915e2de"
      url: "https://pub.dev"
    source: hosted
    version: "11.0.2"
  leak_tracker_flutter_testing:
    dependency: transitive
    description:
      name: leak_tracker_flutter_testing
      sha256: "1dbc140bb5a23c75ea9c4811222756104fbcd1a27173f0c34ca01e16bea473c1"
      url: "https://pub.dev"
    source: hosted
    version: "3.0.10"
  leak_tracker_testing:
    dependency: transitive
    description:
      name: leak_tracker_testing
      sha256: "8d5a2d49f4a66b49744b23b018848400d23e54caf9463f4eb20df3eb8acb2eb1"
      url: "https://pub.dev"
    source: hosted
    version: "3.0.2"
  lints:
    dependency: transitive
    description:
      name: lints
      sha256: "12f842a479589fea194fe5c5a3095abc7be0c1f2ddfa9a0e76aed1dbd26a87df"
      url: "https://pub.dev"
    source: hosted
    version: "6.1.0"
  logging:
    dependency: transitive
    description:
      name: logging
      sha256: c8245ada5f1717ed44271ed1c26b8ce85ca3228fd2ffdb75468ab01979309d61
      url: "https://pub.dev"
    source: hosted
    version: "1.3.0"
  matcher:
    dependency: transitive
    description:
      name: matcher
      sha256: "12956d0ad8390bbcc63ca2e1469c0619946ccb52809807067a7020d57e647aa6"
      url: "https://pub.dev"
    source: hosted
    version: "0.12.18"
  material_color_utilities:
    dependency: transitive
    description:
      name: material_color_utilities
      sha256: "9c337007e82b1889149c82ed242ed1cb24a66044e30979c44912381e9be4c48b"
      url: "https://pub.dev"
    source: hosted
    version: "0.13.0"
  meta:
    dependency: transitive
    description:
      name: meta
      sha256: "23f08335362185a5ea2ad3a4e597f1375e78bce8a040df5c600c8d3552ef2394"
      url: "https://pub.dev"
    source: hosted
    version: "1.17.0"
  path:
    dependency: transitive
    description:
      name: path
      sha256: "75cca69d1490965be98c73ceaea117e8a04dd21217b37b292c9ddbec0d955bc5"
      url: "https://pub.dev"
    source: hosted
    version: "1.9.1"
  sky_engine:
    dependency: transitive
    description: flutter
    source: sdk
    version: "0.0.0"
  source_span:
    dependency: transitive
    description:
      name: source_span
      sha256: "56a02f1f4cd1a2d96303c0144c93bd6d909eea6bee6bf5a0e0b685edbd4c47ab"
      url: "https://pub.dev"
    source: hosted
    version: "1.10.2"
  stack_trace:
    dependency: transitive
    description:
      name: stack_trace
      sha256: "8b27215b45d22309b5cddda1aa2b19bdfec9df0e765f2de506401c071d38d1b1"
      url: "https://pub.dev"
    source: hosted
    version: "1.12.1"
  stream_channel:
    dependency: transitive
    description:
      name: stream_channel
      sha256: "969e04c80b8bcdf826f8f16579c7b14d780458bd97f56d107d3950fdbeef059d"
      url: "https://pub.dev"
    source: hosted
    version: "2.1.4"
  string_scanner:
    dependency: transitive
    description:
      name: string_scanner
      sha256: "921cd31725b72fe181906c6a94d987c78e3b98c2e205b397ea399d4054872b43"
      url: "https://pub.dev"
    source: hosted
    version: "1.4.1"
  term_glyph:
    dependency: transitive
    description:
      name: term_glyph
      sha256: "7f554798625ea768a7518313e58f83891c7f5024f88e46e7182a4558850a4b8e"
      url: "https://pub.dev"
    source: hosted
    version: "1.2.2"
  test_api:
    dependency: transitive
    description:
      name: test_api
      sha256: "93167629bfc610f71560ab9312acdda4959de4df6fac7492c89ff0d3886f6636"
      url: "https://pub.dev"
    source: hosted
    version: "0.7.9"
  vector_math:
    dependency: transitive
    description:
      name: vector_math
      sha256: d530bd74fea330e6e364cda7a85019c434070188383e1cd8d9777ee586914c5b
      url: "https://pub.dev"
    source: hosted
    version: "2.2.0"
  vm_service:
    dependency: transitive
    description:
      name: vm_service
      sha256: "45caa6c5917fa127b5dbcfbd1fa60b14e583afdc08bfc96dda38886ca252eb60"
      url: "https://pub.dev"
    source: hosted
    version: "15.0.2"
sdks:
  dart: ">=3.11.0 <4.0.0"
  flutter: ">=3.35.0"
```

</details>


### Steps to reproduce

**Reproduction repository:** https://github.com/davidmigloz/flutter_block_then_bug
**Live demo:** https://davidmigloz.github.io/flutter_block_then_bug/

### Steps to reproduce

1. Clone the reproduction repository:
   ```bash
   git clone https://github.com/davidmigloz/flutter_block_then_bug.git
   cd flutter_block_then_bug
   flutter pub get
   flutter run -d chrome
   ```

2. The app starts **authenticated** on `/home`.

3. Tap **"Sign Out (set false)"** to toggle `isAuthenticated` to `false`.

4. This triggers `refreshListenable`, which re-evaluates the `onEnter` guard. The guard returns:
   ```dart
   Block.then(() => router.go('/login'));
   ```

5. **Expected:** The app navigates to `/login` (green "FIXED" indicator).

6. **Actual:** The app stays on `/home` (red "BUG" indicator). The debug console confirms the callback fires (`[Block.then] Calling router.go(/login)`), but the navigation is silently lost.

### Minimal code

```dart
final isAuthenticated = ValueNotifier<bool>(true);

GoRouter(
  initialLocation: '/home',
  refreshListenable: isAuthenticated,
  onEnter: (context, current, next, router) {
    if (next.matchedLocation == '/login') return const Allow();

    if (!isAuthenticated.value) {
      return Block.then(() => router.go('/login'));
    }
    return const Allow();
  },
  routes: [
    GoRoute(path: '/home', builder: (_, _) => HomeScreen()),
    GoRoute(path: '/login', builder: (_, _) => LoginScreen()),
  ],
);

// Toggling this triggers the bug:
isAuthenticated.value = false;
```

### Key observation

The same `Block.then(() => router.go('/login'))` works correctly when triggered by imperative navigation (`router.go('/protected')`), but **fails** when triggered by `refreshListenable`. The difference is that `refreshListenable` triggers route re-evaluation via `notifyListeners()` -> `_processRouteInformation`, and the callback's `router.go()` causes a re-entrant parse whose result is discarded by Flutter's Router transaction token mechanism.


### Expected results

When `refreshListenable` fires and the `onEnter` guard returns `Block.then(() => router.go('/login'))`, the app should navigate to `/login`.

The `then` callback documentation states it is "executed after the decision is committed" — so `router.go()` inside it should start a fresh navigation that commits normally, regardless of whether the guard was triggered by imperative navigation or by `refreshListenable`.


### Actual results

The app stays on `/home`. The `Block.then` callback fires (confirmed by debug logs: `[Block.then] Calling router.go(/login)`), but the navigation to `/login` is silently lost. No error or warning is raised.

### Root cause

In `parser.dart`, `handleTopOnEnter` executes the `then` callback synchronously via `await Future<void>.sync(callback)` while the current parse's Future chain is still in-flight. When the callback calls `router.go('/login')`:

1. `GoRouteInformationProvider._setValue` calls `notifyListeners()` **synchronously**
2. Flutter's `Router` receives the notification and starts a new `_processRouteInformation`, minting a new transaction token (TokenB), replacing the outer parse's token (TokenA)
3. The re-entrant `/login` parse (FutureB) is scheduled but hasn't resolved yet
4. `Future.sync(callback)` returns, and the outer `handleTopOnEnter` returns its "stay on current route" `matchList`
5. The outer parse (FutureA) resolves, but `_processParsedRouteInformation` finds TokenA is stale and **silently discards** the result
6. The `/login` parse result is also lost due to the interleaved transaction lifecycle

The net result: `router.go('/login')` fires without error, but the navigation is silently dropped by Flutter's Router transaction token mechanism.

### Why it only fails with `refreshListenable`

The same `Block.then(() => router.go('/login'))` works when triggered by imperative navigation (e.g., `router.go('/protected')`). The difference is the call stack depth and transaction token lifecycle when `refreshListenable` triggers re-evaluation via its own `notifyListeners()` -> `_processRouteInformation` path.


### Code sample

<details open><summary>Code sample</summary>

```dart
[Paste your code here]
```

</details>


### Screenshots or Videos

Full reproduction repository: https://github.com/davidmigloz/flutter_block_then_bug

<details open><summary>Code sample</summary>

```dart
import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';

/// Simulates an auth state that can be toggled.
final ValueNotifier<bool> isAuthenticated = ValueNotifier<bool>(true);

void main() => runApp(const App());

class App extends StatefulWidget {
  const App({super.key});

  @override
  State<App> createState() => _AppState();
}

class _AppState extends State<App> {
  late final GoRouter _router;

  @override
  void initState() {
    super.initState();
    _router = GoRouter(
      initialLocation: '/home',
      refreshListenable: isAuthenticated,
      onEnter: (context, current, next, router) {
        final goingTo = next.matchedLocation;
        debugPrint('[onEnter] authenticated=${isAuthenticated.value}, going to $goingTo');

        // Public routes — always allow
        if (goingTo == '/login') return const Allow();

        // Protected routes — require auth
        if (!isAuthenticated.value) {
          debugPrint('[onEnter] Blocking, returning Block.then(go /login)');
          return Block.then(() {
            debugPrint('[Block.then] Calling router.go(/login)');
            router.go('/login');
          });
        }

        return const Allow();
      },
      routes: [
        GoRoute(path: '/home', builder: (_, _) => const Scaffold(body: Center(child: Text('Home')))),
        GoRoute(path: '/login', builder: (_, _) => const Scaffold(body: Center(child: Text('Login')))),
      ],
    );
  }

  @override
  void dispose() {
    _router.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(routerConfig: _router);
  }
}

// To trigger the bug:
// 1. App starts authenticated on /home
// 2. Toggle: isAuthenticated.value = false;
// 3. refreshListenable fires, guard returns Block.then(() => router.go('/login'))
// 4. Expected: navigates to /login
// 5. Actual: stays on /home — callback navigation silently lost
```

</details>


### Logs

<details open><summary>Logs</summary>

```console
// Debug console output after tapping "Sign Out" (toggling isAuthenticated to false):

[onEnter] authenticated=false, going to /home
[onEnter] Blocking, returning Block.then(go /login)
[Block.then] Calling router.go(/login)
[onEnter] authenticated=false, going to /login

// The guard correctly evaluates, the Block.then callback fires, router.go('/login') is called,
// and onEnter even runs for /login and returns Allow — but the app stays on /home.
// No error or warning is logged. The navigation is silently lost.
```

</details>

### Flutter Doctor output

<details open><summary>Doctor output</summary>

```console
[✓] Flutter (Channel stable, 3.41.2, on macOS 26.3 25D125 darwin-arm64, locale en-US)
    • Flutter version 3.41.2 on channel stable
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 90673a4eef (9 days ago), 2026-02-18 13:54:59 -0800
    • Engine revision 6c0baaebf7
    • Dart version 3.11.0
    • DevTools version 2.54.1

[✓] Android toolchain - develop for Android devices (Android SDK version 36.0.0)
    • Platform android-36, build-tools 36.0.0
    • Java version OpenJDK Runtime Environment (build 21.0.6+-13391695-b895.109)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 26.3)
    • Build 17C529
    • CocoaPods version 1.16.2

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Connected device (2 available)
    • macOS (desktop) • macos  • darwin-arm64   • macOS 26.3 25D125 darwin-arm64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 145.0.7632.117

[✓] Network resources
    • All expected network resources are available.

• No issues found!
```

</details>


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[go_router] Block.then(() => router.go(...)) navigation silently lost when triggered by refreshListenable #183012

What package does this bug report belong to?

What target platforms are you seeing this bug on?

Have you already upgraded your packages?

Dependency versions

Steps to reproduce

Steps to reproduce

Minimal code

Key observation

Expected results

Actual results

Root cause

Why it only fails with `refreshListenable`

Code sample

Screenshots or Videos

Logs

Flutter Doctor output

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

[go_router] Block.then(() => router.go(...)) navigation silently lost when triggered by refreshListenable #183012

Description

What package does this bug report belong to?

What target platforms are you seeing this bug on?

Have you already upgraded your packages?

Dependency versions

Steps to reproduce

Steps to reproduce

Minimal code

Key observation

Expected results

Actual results

Root cause

Why it only fails with refreshListenable

Code sample

Screenshots or Videos

Logs

Flutter Doctor output

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions

Why it only fails with `refreshListenable`