google_identity_services_web

A JS-interop layer for Google Identity's Sign In With Google SDK.

See the original JS SDK reference:

Usage

This package is the Dart JS-interop layer of the new Sign In With Google SDK. Here's the API references for both of the sub-libraries:

id.dart: Sign In With Google JavaScript API reference
oauth2.dart: Google 3P Authorization JavaScript Library for websites - API reference
loader.dart: An (optional) loader mechanism that installs the library and resolves a Future<void> when it's ready.

Loading the SDK

There are two ways to load the JS SDK in your app.

Modify your index.html (most performant)

The most performant way is to modify your web/index.html file to insert a script tag as recommended. Place the script tag in the <head> of your site, next to the script tag that loads flutter.js, so the browser can downloaded both in parallel:

<head>
<!-- ··· -->
  <!-- Include the GSI SDK below -->
  <script src="https://accounts.google.com/gsi/client" async defer></script>
  <!-- This script adds the flutter initialization JS code -->
  <script src="flutter.js" defer></script>
</head>

With the `loadWebSdk` function (on-demand)

An alternative way, that downloads the SDK on demand, is to use the loadWebSdk function provided by the library. A simple location to embed this in a Flutter Web only app can be the main.dart:

import 'package:google_identity_services_web/loader.dart' as gis;
// ···
void main() async {
  await gis.loadWebSdk(); // Load the GIS SDK
  // The rest of your code...
// ···
}

(Note that the above won‘t compile for mobile apps, so if you’re developing a cross-platform app, you'll probably need to hide the call to loadWebSdk behind a conditional import/export.)

Using the SDK

Once the SDK has been loaded, it can be used by importing the correct library:

import 'package:google_identity_services/id.dart'; for Authentication.
- This will expose an id JSObject that binds to google.accounts.id.
import 'package:google_identity_services/oauth2.dart'; for Authorization.
- This will expose an oauth2 JSObject that binds to google.accounts.oauth2.

Troubleshooting

Watch the browser's development tools JS console while using this package. Information about errors during initialization and use of the library will be displayed there.

Some common issues identified so far:

The given origin is not allowed for the given client ID

When you perform local tests or development, you must add both http://localhost and http://localhost:<port_number> to the Authorized JavaScript origins box. The Referrer-Policy response header must also be set to no-referrer-when-downgrade when using http and localhost.

Read more: Sign In with Google for Web - Setup - Get your Google API client ID.

Browser compatibility

The new SDK is introducing concepts that are on track for standardization to most browsers, and it might not be compatible with older browsers.

Refer to the official documentation site for the latest browser compatibility information of the underlying JS SDK:

Sign In With Google > Supported browsers and platforms

Testing

This web-only package uses dart:test to test its features. They can be run with dart test -p chrome.

(Look at test/README.md and tool/run_tests.dart for more info.)