Repository: flutter
Issue: [go_router] ShellRoutes seem to cause NavigatorObserver to not fire (5.0.1)
Labels: package,has reproducible steps,P2,p: go_router,found in release: 3.3,found in release: 3.4,team-go_router,triaged-go_router

## Steps to Reproduce

See the code below, or [this repo](https://github.com/jonmountjoy/navShell).  

**Expected results:** 

I would expect `didPush` in `NavigatorObserver` to be called for every navigation to any page.

**Actual results:** 

It doesn't get called at all, except for the page `b/details` possibly because it's using a `_rootNavigatorKey`?

So in the app, if you click on each tab, and each detail page, (and back again), you only see two logs:

```
[MyNavObserver] didPush: route(/b/details: {}), previousRoute= route(: {})
[MyNavObserver] didPop: route(/b/details: {}), previousRoute= route(: {})
```

<details>
<summary>Code sample</summary>

```dart
// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';
import 'package:logging/logging.dart';

final GlobalKey<NavigatorState> _rootNavigatorKey =
    GlobalKey<NavigatorState>(debugLabel: 'root');
final GlobalKey<NavigatorState> _shellNavigatorKey =
    GlobalKey<NavigatorState>(debugLabel: 'shell');

// This scenario demonstrates how to set up nested navigation using ShellRoute,
// which is a pattern where an additional Navigator is placed in the widget tree
// to be used instead of the root navigator. This allows deep-links to display
// pages along with other UI components such as a BottomNavigationBar.
//
// This example demonstrates how to display a route within a ShellRoute and also
// push a screen using a different navigator (such as the root Navigator) by
// providing a `parentNavigatorKey`.

void main() {
  runApp(ShellRouteExampleApp());
}

/// An example demonstrating how to use [ShellRoute]
class ShellRouteExampleApp extends StatelessWidget {
  /// Creates a [ShellRouteExampleApp]
  ShellRouteExampleApp({Key? key}) : super(key: key);

  final GoRouter _router = GoRouter(
    observers: <NavigatorObserver>[MyNavObserver()],
    debugLogDiagnostics: true,
    navigatorKey: _rootNavigatorKey,
    initialLocation: '/a',
    routes: <RouteBase>[
      /// Application shell
      ShellRoute(
        navigatorKey: _shellNavigatorKey,
        builder: (BuildContext context, GoRouterState state, Widget child) {
          return ScaffoldWithNavBar(child: child);
        },
        routes: <RouteBase>[
          /// The first screen to display in the bottom navigation bar.
          GoRoute(
            path: '/a',
            builder: (BuildContext context, GoRouterState state) {
              return const ScreenA();
            },
            routes: <RouteBase>[
              // The details screen to display stacked on the inner Navigator.
              // This will cover screen A but not the application shell.
              GoRoute(
                path: 'details',
                builder: (BuildContext context, GoRouterState state) {
                  return const DetailsScreen(label: 'A');
                },
              ),
            ],
          ),

          /// Displayed when the second item in the the bottom navigation bar is
          /// selected.
          GoRoute(
            path: '/b',
            builder: (BuildContext context, GoRouterState state) {
              return const ScreenB();
            },
            routes: <RouteBase>[
              /// Same as "/a/details", but displayed on the root Navigator by
              /// specifying [parentNavigatorKey]. This will cover both screen B
              /// and the application shell.
              GoRoute(
                path: 'details',
                parentNavigatorKey: _rootNavigatorKey,
                builder: (BuildContext context, GoRouterState state) {
                  return const DetailsScreen(label: 'B');
                },
              ),
            ],
          ),
        ],
      ),
    ],
  );

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      title: 'Flutter Defmo',
      theme: ThemeData(
        primarySwatch: Colors.red,
      ),
      routeInformationParser: _router.routeInformationParser,
      routerDelegate: _router.routerDelegate,
      routeInformationProvider: _router.routeInformationProvider,
    );
  }
}

/// Builds the "shell" for the app by building a Scaffold with a
/// BottomNavigationBar, where [child] is placed in the body of the Scaffold.
class ScaffoldWithNavBar extends StatelessWidget {
  /// Constructs an [ScaffoldWithNavBar].
  const ScaffoldWithNavBar({
    required this.child,
    Key? key,
  }) : super(key: key);

  /// The widget to display in the body of the Scaffold.
  /// In this sample, it is a Navigator.
  final Widget child;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: child,
      bottomNavigationBar: BottomNavigationBar(
        items: const <BottomNavigationBarItem>[
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            label: 'A Screen',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.business),
            label: 'B Screen',
          ),
        ],
        currentIndex: _calculateSelectedIndex(context),
        onTap: (int idx) => _onItemTapped(idx, context),
      ),
    );
  }

  static int _calculateSelectedIndex(BuildContext context) {
    final GoRouter route = GoRouter.of(context);
    final String location = route.location;
    if (location == '/a') {
      return 0;
    }
    if (location == '/b') {
      return 1;
    }
    return 0;
  }

  void _onItemTapped(int index, BuildContext context) {
    switch (index) {
      case 0:
        GoRouter.of(context).go('/a');
        break;
      case 1:
        GoRouter.of(context).go('/b');
        break;
    }
  }
}

/// The first screen in the bottom navigation bar.
class ScreenA extends StatelessWidget {
  /// Constructs a [ScreenA] widget.
  const ScreenA({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            const Text('Screen A'),
            TextButton(
              onPressed: () {
                GoRouter.of(context).go('/a/details');
              },
              child: const Text('View A details'),
            ),
          ],
        ),
      ),
    );
  }
}

/// The second screen in the bottom navigation bar.
class ScreenB extends StatelessWidget {
  /// Constructs a [ScreenB] widget.
  const ScreenB({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            const Text('Screen B'),
            TextButton(
              onPressed: () {
                GoRouter.of(context).go('/b/details');
              },
              child: const Text('View B details'),
            ),
          ],
        ),
      ),
    );
  }
}

/// The details screen for either the A or B screen.
class DetailsScreen extends StatelessWidget {
  /// Constructs a [DetailsScreen].
  const DetailsScreen({
    required this.label,
    Key? key,
  }) : super(key: key);

  /// The label to display in the center of the screen.
  final String label;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Details Screen'),
      ),
      body: Center(
        child: Text(
          'Details for $label',
          style: Theme.of(context).textTheme.headlineMedium,
        ),
      ),
    );
  }
}

/// The Navigator observer.
class MyNavObserver extends NavigatorObserver {
  /// Creates a [MyNavObserver].
  MyNavObserver() {
    log.onRecord.listen((LogRecord e) => debugPrint('$e'));
  }

  /// The logged message.
  final Logger log = Logger('MyNavObserver');

  @override
  void didPush(Route<dynamic> route, Route<dynamic>? previousRoute) {
    log.info('didPush: ${route.str}, previousRoute= ${previousRoute?.str}');
  }

  @override
  void didPop(Route<dynamic> route, Route<dynamic>? previousRoute) =>
      log.info('didPop: ${route.str}, previousRoute= ${previousRoute?.str}');

  @override
  void didRemove(Route<dynamic> route, Route<dynamic>? previousRoute) =>
      log.info('didRemove: ${route.str}, previousRoute= ${previousRoute?.str}');

  @override
  void didReplace({Route<dynamic>? newRoute, Route<dynamic>? oldRoute}) =>
      log.info('didReplace: new= ${newRoute?.str}, old= ${oldRoute?.str}');
}

extension on Route<dynamic> {
  String get str => 'route(${settings.name}: ${settings.arguments})';
}

```

</details>

<details>
<summary>flutter doctor -v</summary>
[✓] Flutter (Channel stable, 3.3.2, on macOS 12.6 21G115 darwin-x64, locale en-GB)
    • Flutter version 3.3.2 on channel stable at /Users/jonmountjoy/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision e3c29ec00c (8 days ago), 2022-09-14 08:46:55 -0500
    • Engine revision a4ff2c53d8
    • Dart version 2.18.1
    • DevTools version 2.15.0

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    • Android SDK at /Users/jonmountjoy/Library/Android/sdk
    • Platform android-33, build-tools 30.0.3
    • ANDROID_HOME = /Users/jonmountjoy/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jre/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.12+0-b1504.28-7817840)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 14.0)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 14A309
    • CocoaPods version 1.11.3

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
</details>