Unique usernames but not unique emails

[dan]

We have a question about user uniqueness.

We want to have multiple users with unique usernames, but duplicate email addresses.

When creating some users, we found FusionAuth wants unique usernames and email addresses. Is there a way to have usernames be unique, but not emails?

[dan]

The recommended course of action is to store the email in the user.data.email field, which is not required to be unique but is still used for activities like 'forgot password' emails. Leave the user.email field blank and use user.username.

That should work. Support for user.data.email was removed in 1.26 and added back in 1.27.2, so avoid version 1.26.* and 1.27.0 and 1.27.1.

[kasir-barati]

Hey @dan,

Would you mind if I ask you to differentiate between uniqueUsername and username both in updateUser and register in FusionAuth Typescript Client?

await fusionAuthClient.updateUser(id, {
  // ...
  user: {
    uniqueUsername: username,
  },
});
await fusionAuthClient.updateUser(id, {
  // ...
  user: {
    username: username,
  },
});
await fusionAuthClient.register('', {
  // ...
  user: {
    username,
  },
});
await fusionAuthClient.register('', {
  // ...
  user: {
    uniqueUsername,
  },
});

Questions

1. If I use username instead of uniqueUsername, then should I enforce uniqueness manually in my NestJS app?
2. If I use uniqueUsername then will I have access to it as preferred_username returned by FusionAuth?

[kasir-barati]

I tried to specify both username and email and I got this error:

{
  statusCode: 400,
  exception: {
    fieldErrors: {
      'user.email': [
        {
          code: '[blank]user.email',
          message: 'You must specify either the [user.email] or [user.username] property. If you are emailing the user you must specify the [user.email].'
        }
      ],
      'user.username': [
        {
          code: '[blank]user.username',
          message: 'You must specify either the [user.email] or [user.username] property. If you are emailing the user you must specify the [user.email].'
        }
      ]
    },
    generalErrors: []
  }
}

So basically I guess my best bet is to manually enforce uniqueness of username in my backend. But it could have been less cumbersome if I could delegate it to FusionAuth.

I guess what I am trying to emphasis here is the fact that just by saving username in user.data we will be able to have both username and email but applying rules such as uniqueness would require more manual labor. Cannot we just tell FusionAuth to make sure that user.data.username should be unique in that app or tenant?

Side note: Since my question is deviating from the OP I'll create a new post and reference this one.