Add another popup

[tomgscs]

The "add another" functionality of django admin (with related object popup) doesn't work with ModelSelect2. The + sign is not displayed on the field.

The functionality seems to appear in v2 documentation but not in v3 documentation.

[jpic]

Well it works for me :

The functionality seems to appear in v2 documentation but not in v3 documentation.

Because in dal v3 it relies purely on admin features (use django-add-another app outside the admin).

Did you try without dal on a normal select field ? Do you see the + sign then ?

[jpic]

Mystery solved. When using a ModelForm that declares a widget like this:

class TForm(forms.ModelForm):
    class Meta:
        model = TModel
        fields = ('name', 'test')
        widgets = {
            'test': autocomplete.ModelSelect2(url='select2_fk')
        }

Then the admin will generate its own ModelChoiceField and wrap its widget with the RelatedFieldWidgetWrapper.

When you register a ModelForm that declares a custom foreign key field as such:

    class PersonForm(forms.ModelForm):
        birth_country = forms.ModelChoiceField(
            queryset=Country.objects.all(),
            widget=autocomplete.ModelSelect2(url='country-autocomplete')
        )

        class Meta:
            model = Person
            fields = ('__all__')

Then Django will override it's foreign key field that has its widget decorated with RelatedFieldWidgetWrapper, with your declared one which does not have the decorator.

This is pretty annoying but understandable: if you specify your own field then Django does not know if it's compatible with its RelatedFieldWidgetWrapper.

Proof:

> /home/jpic/.local/lib/python3.9/site-packages/django/forms/models.py(279)__new__()
-> fields.update(new_class.declared_fields)
(Pdb) l
274  	                message = message % (', '.join(missing_fields),
275  	                                     opts.model.__name__)
276  	                raise FieldError(message)
277  	            # Override default model fields with any custom declared ones
278  	            # (plus, include all the other declared fields).
279  ->	            fields.update(new_class.declared_fields)
280  	        else:
281  	            fields = new_class.declared_fields
282
283  	        new_class.base_fields = fields
284
(Pdb) fields
{'name': <django.forms.fields.CharField object at 0x7f0a251cf0d0>, 'test': <django.forms.models.ModelChoiceField object at 0x7f0a251cf9a0>}
(Pdb) fields.declared_fields
*** AttributeError: 'dict' object has no attribute 'declared_fields'
(Pdb) new_class.declared_fields
{'test': <dal_alight.fields.ModelAlight object at 0x7f0a283b6460>}
(Pdb) new_class.declared_fields['test'].widget
<dal_alight.fields.ModelAlightWidget object at 0x7f0a283b6520>
(Pdb) fields['test'].widget
<django.contrib.admin.widgets.RelatedFieldWidgetWrapper object at 0x7f0a251cfdf0>

Here you can see that Django is about to override it's default field that has the RelatedFieldWidgetWrapper with my own declared field that does not have it.

[jpic]

Solutions:

• use Meta.widgets instead of declaring the field,
• or, if you really want to declare the field: use djhacker to define your field instead of instanciating one in a form class declaration, because then django admin will wrap the widget inside RelatedWidgetWrapper
• or, use django-add-another

[jpic]

Ticket created @ Django https://code.djangoproject.com/ticket/33321

Let's hope they'll agree to do something about it ... 😂