How to Use Supabase Apple OAuth in React Native

Supabase combined with NextJS or Expo makes spinning up a side project in a few hours possible.

Supabase recently added a tutorial for Expo and support for Apple OAuth authentication. However, Apple OAuth does not work out of the box with Expo and Supabase. So I figured I'd write this article and create a GitHub template.

Supabase and Expo

I followed Supabase's Expo quickstart to get basic authentication working in Expo. The quickstart does not mentioned AsyncStorage which is required in lib/supabase.js to get it working.

My final code:

import AsyncStorage from '@react-native-async-storage/async-storage';
import { createClient } from '@supabase/supabase-js';

// https://reactnative.dev/docs/security#storing-sensitive-info
import { supabaseUrl, supabaseAnonKey } from './supabase-keys';

export const supabase = createClient(supabaseUrl, supabaseAnonKey, {
  localStorage: AsyncStorage,
  detectSessionInUrl: false
});

Supabase Apple OAuth with Expo

Next I followed Supabase's tutorial for Apple authentication. I tried to use Supabase's sign in method onClick in my React Native auth component, which doesn't work:

const { user, session, error } = await supabase.auth.signIn({
  provider: 'apple'
});

The user/session/error all will be null. I was a bit worried Apple OAuth on mobile wouldn't be supported by Supabase's Go True library, but I stumbled upon a PR which adds support Fix: Add id_token grant flow

Instead of using Apple as the provider I decided to use Expo's authentication library to get a token and then pass that to Supabase:

import { startAsync, makeRedirectUri } from 'expo-auth-session';

import { supabase } from '../lib/supabase';
import { supabaseUrl } from '../lib/supabase-keys';

const signInWithApple = async () => {
    const returnUrl = makeRedirectUri({ useProxy: false });
    const provider = 'apple';
    const authUrl = `${supabaseUrl}/auth/v1/authorize?provider=${provider}&redirect_to=${returnUrl}`;

    const response = await startAsync({ authUrl, returnUrl });

    if (!response || !response.params?.refresh_token) {
      return;
    }

    await supabase.auth.signIn({
      refreshToken: response.params.refresh_token
    });
};

The full code is available on GitHub. Apple OAuth with Supabase and support for React Native is relatively new. Feedback is always welcome if there's a better way of doing things.