Demo of go_router interface inconsistency between GoRoute build and errorBuilder environments

README.md

This gist demonstrates a difference in behaviour of GoRouteState.of when instantiated in a child constructed via a GoRoute builder method compared to errorBuilder, despite both GoRouteStates having meaning / being in the function arguments.

Check it out here.

main.dart

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

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(const SimpleApp());
}

class SimpleApp extends StatelessWidget {
  const SimpleApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
        routerConfig: GoRouter(routes: [
      GoRoute(path: '/', builder: (context, state) => RouteExplorer(state))
    ], errorBuilder: (context, state) => RouteExplorer(state)));
  }
}

class RouteExplorer extends StatelessWidget {
  final GoRouterState state;
  const RouteExplorer(this.state, {super.key});

  @override
  Widget build(BuildContext context) {
    GoRouterState? fetchedState;
    try {
      fetchedState = GoRouterState.of(context);
    } catch (_) {}
    return Scaffold(
        body: Column(mainAxisAlignment: MainAxisAlignment.center, children: [
      ...[
        state,
        fetchedState
      ].map((s) => Text(s == null ? 'Null state' : 'uri.path = ${s.uri.path}')),
      Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: ['/', '/foo']
              .map((path) => ElevatedButton(
                  onPressed: () => context.go(path), child: Text(path)))
              .toList())
    ]));
  }
}