BUG: SocialLoginSerializer.validate() checks if email exists, however complete_social_login from allauth already created the user, always ending up in error state

[Meess]

Config

Using all-auth social login with Google

# Pipfile
dj-rest-auth = "==6.0.0"
django-allauth = {extras = ["socialaccount"], version = "==0.63.6"}

Using the following settings:

# base_settings.py
ACCOUNT_LOGOUT_ON_GET = True
SOCIALACCOUNT_AUTO_SIGNUP = True
ACCOUNT_USERNAME_REQUIRED = False
ACCOUNT_USER_MODEL_USERNAME_FIELD = 'username'
SOCIAL_ACCOUNT_USER_MODEL_USERNAME_FIELD = 'username'
ACCOUNT_EMAIL_REQUIRED = True
SOCIALACCOUNT_EMAIL_REQUIRED = True
ACCOUNT_AUTHENTICATION_METHOD = 'email'
SOCIALACCOUNT_AUTHENTICATION_METHOD = 'email'

Functional Issue

Not signed up user has to login twice before actually logged in.

The first time a user logs in always results in a ValidationError with message 'User is already registered with this e-mail address.'. However the user is actually created in de db, even though the error occurs. If the user logs in again, it recognises the user in the database and logs you in with status 200 (i.e. user is actually logged in).

Issue

SocialLoginSerializer.validate(..) itself checks if the e-mail adress is already in use on signup, however prior to that is call the all-auth function complete_social_login which already checks this, and saves the user:

SocialLoginSerializer.validate(...) calls allauth's complete_social_login

# /dj_rest_auth/registration/serializers.py
class SocialLoginSerializer(serializers.Serializer):
    def validate(self, attrs):
            ...
            ret = complete_social_login(request, login)

########### START callstack into allauth ###########
# /allauth/socialaccount/helpers.py
def complete_social_login(request, sociallogin):
    ...
    flows.login.complete_login(request, sociallogin)

# /allauth/socialaccount/internal/flows/login.py
def complete_login(request, sociallogin, raises=False):
    ...
    return _authenticate(request, sociallogin)

def _authenticate(request, sociallogin):
    ...
    ret = process_signup(request, sociallogin)

# /allauth/socialaccount/internal/flows/signup.py
def process_signup(request, sociallogin):
    ...
    # Here the user get's saved by allauth, and returns to where dj-rest-auth's SocialLoginSerializer.validate
    # called complete_social_login (where it goes wrong.)
    get_adapter().save_user(request, sociallogin, form=None)
########### END callstack into allauth ###########

# /dj_rest_auth/registration/serializers.py
class SocialLoginSerializer(serializers.Serializer):
    def validate(self, attrs):
            ...
            # Back in dj-rest-auth validation, it tries to validate if the email adress is unique, however
            # the user was just created by all-auth with exactly this email adress, so it will throw an error
            # that the adres is already in use. As the user is already created, a new login follows the login flow
            # instead of the signup flow, and therefore the user can login without issue on the second login
            account_exists = get_user_model().objects.filter(
                    email=login.user.email,
                ).exists()

Possible solution

The returned login variable login.is_existing is checked to see if a user already existed, if not it goes and checks the email adress. However login.user can also be checked, as allauth fills login.user with the created user object on signup, dj-rest-auth could check this and see if it already has an ID. If it has an ID it knows the user is already created (and then assume allauth did proper validation) and hence skip the email check.

Workaround (hacky)

Create a custom SocialLoginSerializer, copy only yhe validate function from the original code and comment out the email check.

# custom_social_login_serializer.py
class CustomSocialLoginSerializer(SocialLoginSerializer):
    def validate(self, attrs):
            ...
            # if allauth_account_settings.UNIQUE_EMAIL:
            #     # Do we have an account already with this email address?
            #     account_exists = get_user_model().objects.filter(
            #         email=login.user.email,
            #     ).exists()
            #     if account_exists:
            #         raise serializers.ValidationError(
            #             _('User is already registered with this e-mail address.'),
            #         )

# social_providers.py
from dj_rest_auth.registration.views import SocialLoginView
from allauth.socialaccount.providers.google.views import GoogleOAuth2Adapter
from allauth.socialaccount.providers.oauth2.client import OAuth2Client
from .custom_social_login_serializer import CustomSocialLoginSerializer

class GoolgeAuth(SocialLoginView):
    adapter_class = GoogleOAuth2Adapter
    client_class = OAuth2Client
    serializer_class = CustomSocialLoginSerializer

[benshaji-sequoiaat]

Hi, it seems this is a similar issue: #658