Allow easier reuse of AuthenticationForm invalid_login ValidationError

[Jon Dufresne]

The AuthenticationForm contains the ​snippet in the clean method:

    def clean(self):
        username = self.cleaned_data.get('username')
        password = self.cleaned_data.get('password')

        if ...:
            ...
            if ... is None:
                raise forms.ValidationError(
                    self.error_messages['invalid_login'],
                    code='invalid_login',
                    params={'username': self.username_field.verbose_name},
                )
        ...

In my project, I have overridden AuthenticationForm with customizations. Among these customizations, I have other reasons for raising an invalid_login. Rather than copy round the:

                raise forms.ValidationError(
                    self.error_messages['invalid_login'],
                    code='invalid_login',
                    params={'username': self.username_field.verbose_name},
                )

I suggest the form wrap this in a small function for reuse.

I'm not sure if this requires documentation or can remain an internal implementation detail. I'm happy to also add documentation if it is a good idea.

[Jon Dufresne]

​PR

[Claude Paroz]

Looks good, I don't think documentation is required here.

[Tim Graham <timograham@…>]

In 6ed347d:

Fixed #28706 -- Moved AuthenticationFormn invalid login ValidationError to a method for reuse.