Difficult to subclass FieldBase for custom ModelChoiceFields

i’m trying to build a custom autocomplete multiple model choice field. i started like this:

class SortedModelMultipleChoiceField(autocomplete_light.FieldBase, SortedMultipleChoiceField):
    pass

But that results in a TypeError: __init__() takes at least 2 arguments (2 given) because ‘queryset’ is not in kwargs.

This is because parents in https://github.com/yourlabs/django-autocomplete-light/blob/master/autocomplete_light/fields.py#L33 doesn’t return forms.ModelMultipleChoiceField in my case; it only returns (<class 'autocomplete_light.fields.FieldBase'>, <class 'sortedm2m.forms.SortedMultipleChoiceField'>) even though sortedm2m.forms.SortedMultipleChoiceField is a subclass of forms.ModelMultipleChoiceField

Using __mro__ instead of __bases__ would solve the check.

For the time being, i’m just declaring the field this way:

class SortedModelMultipleChoiceField(autocomplete_light.FieldBase, SortedMultipleChoiceField, forms.ModelMultipleChoiceField):
    """
    forms.ModelMultipleChoiceField is required as a parent class, even though 
    it's a parent class of SortedMultipleChoiceField
    """
    pass

[carlos22]

Since v3 is completely different, is there a similar approach to use dal with sortedm2m?

[smcoll]

For the record, with this fix in addition to #331 , making an autocomplete version of sortedm2m’s SortedMultipleChoiceField was super clean:

import autocomplete_light
from sortedm2m.forms import SortedMultipleChoiceField


class SortedModelMultipleChoiceField(autocomplete_light.FieldBase, SortedMultipleChoiceField):
    """
    Autocomplete ModelMultipleChoiceField with SortedM2M support
    """
    widget = autocomplete_light.MultipleChoiceWidget