BaseForm __init__ doesn't super and so breaks MI Mixins

[gbauer]

BaseForm's init method doesn't do a super(...) call to follow up the chain, which breaks writing mixins for ModelForms, as the chain is not followed to the classes to the right of the base classes:

class MyForm(ModelForm, ModelFormMixin):

... do stuff

Inheritance will follow ModelForm up the chain until it hits BaseForm and then stop following up further, but ModelFormMixin is in the mro after the mro of ModelForm and so will never looked at. Just adding a super(BaseForm, self).init(.....) to the BaseForm init will work wonders there ...

[Matthias Kestenholz]

This is a bit harder than it looks at first sight. According to ​http://fuhm.net/super-harmful/ , every single argument should be passed on. However, this obviously won't work when there aren't any mixins around, just object, because object does not accept any arguments in init.

On the other hand, standard subclassing of Form expects all arguments BaseForm itself accepts too.

Depending on the mro, mixins/subclasses will have to accept either *args/kwargs or nothing.

I'm not sure how we should fix this issue.

[Valentin Golev]

We could choose a class-based generic views way: add a self.args/self.kwargs parameter (or self._args/self._kwargs maybe)

[Łukasz Rekucki]

I would vote for "won't fix" on this. The proper way to write this is:

class MyForm(ModelFormMixin, ModelForm):
    pass

I don't see a reason why a mixin should be later in MRO then the class it extends. If the mixin is unrelated to ModelForm then putting it in front won't hurt either. This is also how class-based views use mixins.

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Aymeric Augustin]

Change Easy pickings from NULL to False.

[Claude Paroz]

Closing based on comment:5