[Auth] Anonymous to permanent account

[gwenoleR]

Hi !

I'm a little bit confused with the concept of Linking credentials.

In my app by default users are connected Anonymously.
They can signin later using their phone number.

So I want to link their previous anonymous user to their permanent account.

It's working fine if the permanent account is not already exists, but it throw me an error when a User tried to connect to his existing account [Error: [auth/credential-already-in-use] This credential is already associated with a different user account.]

👇 Use case example

• Alice just download our app and launch it for the first time. She is connected anonymously with an id abcd1234.
• She decides now, to create an account because she really likes our app. She enters her phone number and now she has a permanent account with her phone number with the id abcd1234
• For some reason, Alice decides to SignOut. So now, she is an anonymous user again, with a new id wxyz987.
• When she try to connect again with her phone number, this error his thrown [Error: [auth/credential-already-in-use] This credential is already associated with a different user account.]

I thought we could link as many anonymous users as we wanted to the same permanent account, but it seems that's not possible, or am I doing something wrong?

Here the snippet that links account:

async signIn(...[verificationId, code]: [string, string]) {
    const credential = auth.PhoneAuthProvider.credential(verificationId, code)

    const anonymousUser = this.user

    if (anonymousUser) {
      await anonymousUser
        .linkWithCredential(credential)
        .catch((e) => console.log(e))
    }
    return await auth().signInWithCredential(credential)
  }