allauth ACCOUNT_UNIQUE_EMAIL doesn't work as expected

[dontic]

There is an edge case when using email as the authentication method as well as email verification. The server will crash if the user hasn't verified the email but a new registration with that same email is tried.

Steps to reproduce:

1. Set the following allauth settings

ACCOUNT_AUTHENTICATION_METHOD = "email"  # username, email or username_email
ACCOUNT_USER_MODEL_USERNAME_FIELD = None
ACCOUNT_EMAIL_REQUIRED = True  # Needs to be True to use email as the auth method
ACCOUNT_USERNAME_REQUIRED = False
ACCOUNT_UNIQUE_EMAIL = True
ACCOUNT_EMAIL_VERIFICATION = "mandatory"  # "none", "optional", "mandatory"

2. Register a new email
3. Try to register the same email without first validating it

Analysis

I found that this edge case is not handled in the serializer:

def validate_email(self, email):
    email = get_adapter().clean_email(email)
    if allauth_account_settings.UNIQUE_EMAIL:
        if email and EmailAddress.objects.is_verified(email):
            raise serializers.ValidationError(
                _("A user is already registered with this e-mail address."),
            )
    return email

The validation error for unique email is only raised if the account has been verified.

Here's a proposed fix:

def validate_email(self, email):
    email = get_adapter().clean_email(email)
    if allauth_account_settings.UNIQUE_EMAIL:
        if email and EmailAddress.objects.is_verified(email):
            raise serializers.ValidationError(
                _("A user is already registered with this e-mail address."),
            )
        else:
            query = EmailAddress.objects.filter(email__iexact=email)
            if query.exists():
                email_address = query.first()
                if email_address.user.has_usable_password():
                    raise serializers.ValidationError(
                        _("A user is already registered with this e-mail address but hasn't been verified their email yet."),
                    )
    return email

The wording is not the best and can be changed.

Tested and working:

Opened #618

[danryu]

Just ran into this issue myself.
Though I am configuring with
ACCOUNT_EMAIL_VERIFICATION ="optional"
but I think your fix will work in this use-case as well.