Make AuthenticationForm use the username length from the user model

[Ramin Farajpour Cami]

AuthenticationForm has a hardcoded max_length=254 (#19130). It might be able to use the max length from the user model with something like: self.fields['username'].max_length = UserModel._meta.get_field(UserModel.USERNAME_FIELD).max_length in AuthenticationForm.__init__().

[Tim Graham]

The suggestion doesn't account for custom user models and undoes #19130 (you might try using git blame to investigate history next time).

If the current situation is problematic for you, perhaps there would be some value in setting the max length based on the custom user model ​as Claude suggested .

[Ramin Farajpour Cami]

User model use max_length=150,also in add user form set 150,
What your means "value setting the max length based on the custom user model"?

[Tim Graham]

​Custom user models may have a username with length other than 150, that's why using that value isn't appropriate. We might be able to use that with something like this: self.fields['username'].max_length = UserModel._meta.get_field(UserModel.USERNAME_FIELD).max_length.