Firebase Convert Anonymous User Account to Permanent Account Error

You should not call createUserWithEmailAndPassword to upgrade the anonymous user. This will sign up a new user, signing out the currently signed in anonymous user.

All you need is the email and password of the user. IDP providers (e.g. Google, Facebook), on the contrary, will require to complete their full sign in flow to get their tokens to identify the user. We do recommend to use linkWithPopup or linkWithRedirect for these, though.

Example:

// (Anonymous user is signed in at that point.)

// 1. Create the email and password credential, to upgrade the
// anonymous user.
var credential = firebase.auth.EmailAuthProvider.credential(email, password);

// 2. Links the credential to the currently signed in user
// (the anonymous user).
firebase.auth().currentUser.linkWithCredential(credential).then(function(user) {
  console.log("Anonymous account successfully upgraded", user);
}, function(error) {
  console.log("Error upgrading anonymous account", error);
});

Let me know if that works!

After you log in as an Anonymous user, run this code to raise Popup and connect your anon user wit some OAUTH provider

const provider = new firebase.auth.FacebookAuthProvider()
firebase.auth().currentUser.linkWithPopup(provider)
console.log(provider)