How to make Django username field of LoginView(FormView) lowercase?

Question

I've made it so that any user that signs up with a username will automatically have their username converted to lowercase. user/forms.py

I now have the issue where I can't figure a way to convert the username in the login form to become lower when submitted. As I would still like the user to be able to enter their name in the case of their choice.

I've tried the python tolower() function on a few things in the LoginView, yet unsuccessful. If anyone has an idea on how I could achieve this please let me know.

Here is the user/forms.py

class UserSignupForm(UserCreationForm):
    email = forms.EmailField()

    class Meta:
        model = User
        fields = ["username", "email", "password1", "password2"]

    def clean_username(self):
        username = self.cleaned_data["username"].lower()

        if not re.match(r"^[A-Za-z0-9_]+$", username):
            raise forms.ValidationError(
                "Sorry , you can only have alphanumeric, _ or - in username"
            )
        else:
            return username

Here is the user/urls.py

path("signup/", user_view.signup, name="signup"),
path("login/",auth_view.LoginView.as_view(template_name="user/login.html"),name="login"),

Answer 1

You can subclass the AuthenticationForm:

# app_name/forms.py

from django.contrib.auth.forms import AuthenticationForm

class MyAuthenticationForm(AuthenticationForm):

    def clean_username(self):
        return self.cleaned_data['username'].lower()

then you inject that form in the LoginView:

from app_name.forms import MyAuthenticationForm

# …

path('login/',
    auth_view.LoginView.as_view(
        form_class=MyAuthenticationForm,
        template_name='user/login.html'
    ),
    name='login'
)