`BaseModelFormSet` ignore form's widgets options when adding the pk field

[Simon Charette]

When defining a custom widget for the pk field of a modelform used in a modelformset this way:

class MyModelForm(forms.ModelForm):
    class Meta:
        model = MyModel
        widgets = {
          'id': forms.HiddenInput(attrs={'class': 'a-useful-class'})
        }

MyFormSet = modelformset_factory(MyModel, MyModelForm)

The specified widget is ignored because of ​this line.

It should be replaced by something along

widget = form._meta.widgets.get(self._pk_field.name, HiddenInput)
form.fields[self._pk_field.name] = ModelChoiceField(qs, initial=pk_value, required=False, widget=widget)

I'll provide patch with tests if this gets accepted.

[Claude Paroz]

I see no reason why the pk field wouldn't respect the widgets dict. Patch welcome!

[Simon Charette]

Fix with tests

[Simon Charette]

Added patch with tests. Note that I also corrected regressiontests.model_formsets.regress.CustomWidget (introduced for #13095) to actually be a widget and not a field subclass.

[Adrien Lemaire]

Good

[Simon Charette <charette.s@…>]

In a097ee32d8364045a950d6a36b19630fc34397f1:

Fixed #17683 -- Make sure BaseModelFormSet respects defined widgets.