Extra value is null when Widget inspector is open

[diegoveloper]

The extra from GoRouterState is null when the Widget inspector is open with the toggle SELECT WIDGET MODE is enabled and the current page extract data from the GoRouterState (extra).

Video:

https://user-images.githubusercontent.com/4898256/155167172-4e6924bd-f71b-49e6-be25-2884ce39e593.mov

Code to reproduce this issue:

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

void main() {
  runApp(const MyApp());
}

GoRouter _router = GoRouter(
  initialLocation: '/splash',
  debugLogDiagnostics: true,
  observers: [],
  routes: [
    GoRoute(
      path: '/splash',
      pageBuilder: (context, state) => CustomTransitionPage<void>(
        key: state.pageKey,
        child: const SplashPage(),
        transitionsBuilder: (context, animation, animation2, child) {
          return FadeTransition(
            opacity: animation,
            child: child,
          );
        },
      ),
    ),
    GoRoute(
      name: 'login',
      path: '/login',
      builder: (context, state) => LoginPage(user: state.extra! as String),
    ),
  ],
);

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      routeInformationParser: _router.routeInformationParser,
      routerDelegate: _router.routerDelegate,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
    );
  }
}

class SplashPage extends StatefulWidget {
  const SplashPage({Key? key}) : super(key: key);

  @override
  State<SplashPage> createState() => _SplashPageState();
}

class _SplashPageState extends State<SplashPage> {
  Future<void> _checkSplash() async {
    await Future.delayed(const Duration(seconds: 2));
    context.go('/login', extra: "Diego");
  }

  @override
  void initState() {
    _checkSplash();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      backgroundColor: Colors.white,
      body: const Center(
        child: CircularProgressIndicator(),
      ),
    );
  }
}

class LoginPage extends StatefulWidget {
  const LoginPage({required this.user, Key? key}) : super(key: key);
  final String user;

  @override
  State<LoginPage> createState() => _LoginPageState();
}

class _LoginPageState extends State<LoginPage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('LOGIN'),
      ),
      body: Center(
        child: Text('user: ${widget.user}'),
      ),
    );
  }
}