[LightDM] Authentication with no passwords

[David Edmundson]

Sort of related to my previous email, I have a problem with logging in
user's where no password is required to log in, such as those in the
nopasswd group.

My code reads (in pseudocode):

greeer.authenticateUser("foo");
onPrompt() {
    greeer.respond(..);
}
onAuthenticationComplete() {
    if (greeter.authenticated) {
        greeter.startSessionSync
    } else {
        showError()
    }
}

In the case where no password is required, the backend goes straight
from authenticateUser to the onAuthenticationComplete callback,
however greeter.authenticated is false so my login fails. How is the
workflow meant to go?

David Edmundson