Not working for multiple levels of inheritance

[kekomal]

When the mixin is added to a parent abstract model, it does not add the fields to the child.

In my case, this approach to the receiver works better:

def mixin_step(target, clazz):
    for base in clazz.__bases__:
        if issubclass(base, ModelMixin):
            if ModelMixin in base.__bases__:
                base.model_mixin(target)
            mixin_step(target, base)

@receiver(class_prepared)
def mixin(sender, **kwargs):
    mixin_step(sender, sender)

I'm afraid this approach can give problems for non-abstract parent models (it was not my case, so I haven't tested it), so maybe the next approach is better:

def mixin_step(target, clazz):
    for base in clazz.__bases__:
        if issubclass(base, ModelMixin):
            if ModelMixin in base.__bases__:
                base.model_mixin(target)
            try:
                if not (issubclass(base, models.Model) and not base._meta.abstract):
                    mixin_step(target, base)
            except: pass

@receiver(class_prepared)
def mixin(sender, **kwargs):
    mixin_step(sender, sender)

I'm sure this solution can be polished. I only wanted to comment the issue and prompt to a feasible solution.

Regards,
Eneko