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    [CodeWithSwiz 19] Firebase Auth support in useAuth, pt1

    Support for Firebase Auth is one of the most requested features for useAuth and I figured what the heck, how hard can it be?

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    Friend, it can be very hard. Google docs are shit. The perfect example of For Engineers, By Engineers.

    You find out everything that's possible. All the little trees, every detail. Want user/pass auth? Here's the code. Email link? Do this. OAuth with xyz provider? Here.

    You know what they don't say?

    How to set up fricken Firebase 😡

    The setup

    // Initialize the FirebaseUI Widget using Firebase.
    var ui = new firebaseui.auth.AuthUI(firebase.auth())

    Ok Google, how do I import this? Where's my API key?

    Is there Google magic afoot and they can guess? Ask me after initialization like the Netlify Identity widget can?


    Firebase error about missing configuration
    Firebase error about missing configuration

    We later found the right docs to follow for initial setup. Even explains how to correctly import for a smaller bundle size.

    pt2 will go swimmingly 💪

    Creating an auth provider for useAuth

    My favorite result of refactoring useAuth from React.Context to XState is that we can support multiple auth providers. Core logic is the same, details pluggable.

    useAuth state machine
    useAuth state machine

    There's an abstraction layer and basic documentation on what to do. We're putting my docs to the test 😅

    1. stub your provider

    You start with copypasta of the abstract implementation.

    // src/providers/YourThing.ts
    // Auth Wrapper for Auth0
    export class Auth0 implements AuthProviderClass {
      private auth0: Auth0Client.WebAuth
      private dispatch: (eventName: string, eventData?: any) => void
      // Auth0 specific, used for roles
      private customPropertyNamespace?: string
      // Initialize the client and save any custom config
      constructor(params: AuthOptions) {
        // You will almost always need access to dispatch
        this.dispatch = params.dispatch
        // Auth0 specific, used for roles
        this.customPropertyNamespace = params.customPropertyNamespace
        // Init your client
        this.auth0 = new Auth0Client.WebAuth({
          ...(params as Auth0Options),
      // Makes configuration easier by guessing default options
      static addDefaultParams(params: ProviderOptions, callbackDomain: string) {
        const vals = params as Auth0Options
        return {
          redirectUri: `${callbackDomain}/auth0_callback`,
          audience: `https://${vals.domain}/api/v2/`,
          responseType: "token id_token",
          scope: "openid profile email",
      public authorize() {
        // Open login dialog
      public signup() {
        // Open signup dialog
      public logout(returnTo?: string) {
        // Logs user out of the underlying service
      public userId(user: Auth0UserProfile): string {
        // Return the userId from Auth0 shape of data
      public userRoles(user: AuthUser): string[] | null {
        // Return user roles from Auth0 shape of data
      public async handleLoginCallback(): Promise<boolean> {
        // Handle login data after redirect back from service
        // Dispatch ERROR on error
        // Dispatch AUTHENTICATED on success
        // include the user object and authResult with at least an expiresIn value
      public async checkSession(): Promise<{
        user: Auth0UserProfile
        authResult: Auth0DecodedHash
      }> {
        // verify session is still valid
        // return fresh user info

    2. fill abstract implementation

    Fill in those methods to fit your auth provider. Here's what we tried for Firebase Auth. Don't know yet if it works.

    // src/providers/FirebaseUI.ts
    constructor(params: AuthOptions) {
        // You will almost always need access to dispatch
        this.dispatch = params.dispatch;
        // Init your client
        this.ui = new FirebaseAuthUI.AuthUI(firebase.auth());
    public authorize() {
        // Open login dialog
        this.ui.start("#firebaseui-auth-container", {
            signInOptions: [firebase.auth.EmailAuthProvider.PROVIDER_ID]

    Don't quote me on that yet :)

    3. use the provider

    Use in your app. We created a Gatsby-based example on stream

    // gatsby-browser.js
    export const wrapRootElement = ({ element }) => (
      <ThemeProvider theme={theme}>
              /* ... */

    Render <AuthConfig> and provide the new auth provider. We don't know yet which params Firebase Auth is going to use. Find out next time :)

    4. contribute to useAuth 🙏🏻

    To contribute the FirebaseUI auth provider to the core library we needed an extra step 👉 adding it to the library.

    That happens in package.json:

        "source": [
        // ...
        "files": [

    The "source" config tells microbundle to build FirebaseUI.ts as its own library. Creates a bunch of files in dist/* that aren't connected with the rest.

    The "files" config tells NPM to keep ./firebase-ui.js when publishing. That file is a hack.

    // ./firebase-ui.js
    // this is a hack to improve DX
    // TODO: figure out a better way
    const { FirebaseUI } = require("./dist/FirebaseUI")
    module.exports = { FirebaseUI }

    Only way I could find to:

    1. Reduce bundle size and let you use different providers without installing all of them
    2. Have understandable imports like import FirebaseUI from "react-use-auth/firebase-ui"

    If you know a better way please hit reply.

    In conclusion

    Understanding beats knowledge. Knowing how several details of Firebase work, does not mean you can make it fit together.

    Keep that in mind next time you write docs for your team.


    PS: it's beyond cool that TypeScript lets you define "An auth provider must conform to this API" and enforces it at the compiler level. Makes this way easier 😍

    Published on January 12th, 2021 in CodeWithSwiz, Technical, Firebase, useAuth, Livecoding, State machines

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