Expo Google Auth Module

Common errors

• Failed to authenticate. ID token is null or undefined.

  cause Google credentials (e.g., Google Web Client ID, SHA-1 fingerprints for Android) are incorrectly configured or missing in the Google Cloud Console.
  fix Verify that your Google Web Client ID is correct, the Android client is registered with the correct package name and SHA-1 fingerprint in the Google Cloud Console, and ensure the API is enabled.

• TypeError: ExpoGoogleAuth.launchGoogleAuth is not a function

  cause This error typically occurs when attempting to use CommonJS `require()` syntax with an ESM-only package, or when TypeScript/Babel transpilation is misconfigured.
  fix Ensure you are using `import ExpoGoogleAuth from 'expo-google-auth';` in your JavaScript/TypeScript files. If using CommonJS, consider project-wide migration to ESM or using dynamic import.

• Module not found: Can't resolve 'expo-google-auth'

  cause The package `expo-google-auth` has not been installed, or there's a typo in the import path.
  fix Run `npm install expo-google-auth` or `yarn add expo-google-auth` in your project directory. Double-check the spelling of the import path.

Warnings

• gotcha This module currently provides native Google authentication support exclusively for Android. For iOS applications, developers are explicitly advised to use `expo-auth-session`.
  Fix: For iOS, implement Google authentication using `expo-auth-session` as recommended in the official Expo documentation.
• gotcha Successful Google authentication requires proper setup of Google Credentials, including obtaining a Google Web Client ID (GWC ID) and configuring it in the Google Cloud Console for your Android application (and potentially web client).
  Fix: Refer to Google's Identity API documentation and Expo's guides for setting up Google Credentials, ensuring your GWC ID and Android SHA-1 fingerprints are correctly configured.
• gotcha The `launchGoogleAuth` method accepts two string arguments: 'GID' (recommended) or 'SWIG' (traditional). While both may work, Google's latest recommendations favor the 'GID' approach.
  Fix: Always prefer `ExpoGoogleAuth.launchGoogleAuth("GID", gwcId)` for the most current and recommended Google Identity API integration.

Install

• npm install expo-google-auth npm
• yarn add expo-google-auth yarn
• pnpm add expo-google-auth pnpm

Imports

• ExpoGoogleAuth
  wrong:

  const ExpoGoogleAuth = require('expo-google-auth');

  correct:

  import ExpoGoogleAuth from 'expo-google-auth';

  Primarily designed for ESM usage within Expo/React Native projects. CommonJS `require` is not officially supported and may lead to issues.

Quickstart

Demonstrates how to initiate Google authentication using the recommended 'GID' method and handle the returned ID token. Includes error handling and prompts for necessary configuration.

import ExpoGoogleAuth from 'expo-google-auth';
import { Alert } from 'react-native'; // For showing results in a real app

const MY_GOOGLE_WEB_CLIENT_ID = process.env.GOOGLE_WEB_CLIENT_ID ?? 'YOUR_GWC_ID_HERE'; // Replace with your actual GWC ID

async function signInWithGoogle() {
  if (MY_GOOGLE_WEB_CLIENT_ID === 'YOUR_GWC_ID_HERE') {
    Alert.alert('Configuration Error', 'Please replace YOUR_GWC_ID_HERE with your actual Google Web Client ID.');
    return;
  }
  try {
    // Method 1: Latest, Recommended by Google
    const idToken = await ExpoGoogleAuth.launchGoogleAuth("GID", MY_GOOGLE_WEB_CLIENT_ID);
    if (idToken) {
      Alert.alert('Sign-in Successful', `Received ID Token: ${idToken.substring(0, 30)}...`);
      console.log('Google ID Token:', idToken);
      // Now, provide this id token to your backend auth provider
    } else {
      Alert.alert('Sign-in Failed', 'No ID token received.');
    }
  } catch (error) {
    console.error('Google Sign-in Error:', error);
    Alert.alert('Sign-in Error', error.message || 'An unknown error occurred during Google sign-in.');
  }
}

// Example of how to call it (e.g., from a button press in a React Native component)
signInWithGoogle();