extend / code / lambdas

Twitter Reconcile Lambda

When a Twitter identity provider is used to complete a federated login request, FusionAuth will use the configured linking strategy to reconcile the user. FusionAuth will attempt to match the user information returned from the Twitter identity provider to an existing user account or create a new one.

You may optionally utilize a lambda to customize the user and user registration during the authentication event.

When you create a new lambda using the FusionAuth administrative user interface, you will be provided an empty function to implement.

Lambda Structure

If you are using the API to create the lambda you will need to ensure your function has the following signature:

function reconcile(user, registration, twitterUser) {
  // Lambda code goes here
}

This lambda must contain a function named reconcile that takes three parameters. The parameters that the lambda is passed are:

user - the FusionAuth User object. You can modify this object. However, the email and username attributes may not be modified after the user has been linked.
registration - the FusionAuth UserRegistration object. You can modify this object.

twitterUser - the JSON user object returned by the Twitter Verify Credentials API. This object is read-only.

The two FusionAuth objects are well documented in the User API and Registration API documentation. The twitterUser may contain various user claims to utilize during the reconcile process.

Assigning The Lambda

Once a lambda is created, you may assign it to the Twitter identity provider in the IdP configuration.

Navigate to Settings -> Identity Providers and select your existing Twitter configuration or click Add provider and select Twitter if it has not yet been configured.

Example Lambda

There is not a default Twitter reconcile lambda provided by FusionAuth. The following is an example lambda you can use as a starting point.

// This is the default Twitter reconcile, modify this to your liking.
function reconcile(user, registration, twitterUser) {
  // Un-comment this line to see the twitterUser object printed to the event log
  // console.info(JSON.stringify(twitterUser, null, 2));

  // Set name if available in the response
  if (twitterUser.name) {
    user.fullName = twitterUser.name;
  }

  // https://developer.twitter.com/en/docs/accounts-and-users/user-profile-images-and-banners.html
  if (twitterUser.profile_image_url_https) {
    // Remove the _normal suffix to get the original size.
    user.imageUrl = twitterUser.profile_image_url_https.replace('_normal.png', '.png');
  }

  // Set twitter screen_name in registration.
  // - This is just for display purposes, this value cannot be used to uniquely identify
  //   the user in FusionAuth.
  registration.username = twitterUser.screen_name;
}

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