GoRouter in Flutter not recognizing root path deep links without a trailing slash

Question

I'm experiencing an issue with deep linking in a Flutter app, particularly when using GoRouter (version 13.2.1) for navigation. My web app is built with Next.js, hosted on Vercel, and uses a custom domain (www.example.com). I've set up deep linking following the official Flutter documentation, including adding assetlinks.json to the /public/.well-known directory and configuring AndroidManifest.xml as follows:

<meta-data android:name="flutter_deeplinking_enabled" android:value="true" />
<intent-filter android:autoVerify="true">
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.DEFAULT" />
    <category android:name="android.intent.category.BROWSABLE" />
    <data android:scheme="http" android:host="www.example.com" />
    <data android:scheme="https" />
</intent-filter>

With this setup, deep links work as expected, opening the app from URLs shared in other apps. However, the issue arises when integrating GoRouter for in-app navigation with the following basic setup:

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

void main() => runApp(MaterialApp.router(routerConfig: router));

final router = GoRouter(
  routes: [
    GoRoute(
      path: '/',
      builder: (_, __) => Scaffold(appBar: AppBar(title: const Text('Home Screen'))),
      routes: [
        GoRoute(
          path: 'details',
          builder: (_, __) => Scaffold(appBar: AppBar(title: const Text('Details Screen'))),
        ),
      ],
    ),
  ],
);

Navigating to www.example.com/details works flawlessly, but attempting to open www.example.com to reach the HomeScreen ('/' path) triggers a GoException:

GoException: no routes for location: https://www.example.com

Upon investigation, I found that GoRouter receives an empty string instead of '/' for the root path. Here's the state at the time of the exception (logged within onException of GoRouter):

state.error: null
state.path: null
state.fullPath:
state.uri: https://www.example.com
state.topRoute: null
state.extra: null
state.matchedLocation:
state.pageKey: [<'topLevel'>]
state.pathParameters: {}
state.name: null

Interestingly, navigating to www.example.com// (with a double slash) correctly opens the root route ('/'). Neither www.example.com nor www.example.com/ (with a single slash) works as expected. It seems GoRouter anticipates a trailing slash in the domain, but my URL doesn't include one, resulting in routing issues.

Question: What could be causing this discrepancy? I am not sure where should I look for the potential cause - because I am not sure if this is an issue with Vercel, Next.js, or GoRouter. Any insights or solutions to ensure the root URL correctly routes to '/' in GoRouter would be greatly appreciated.

Answer 1

This was an internal issue of the GoRouter package. It should be fixed as of version 13.2.3 and above. If you really have to use a version that has this issue, you can use Joseph Schmoe's solution with redirect.

If you're wondering what was causing this issue, you can check out this PR on GitHub which fixed it.