🐛 Custom attributes defined in result_from_instance are not present for default value

[tomas-nz]

Bug Description

Method result_from_instance is not called for a default (initial) value. Only method label_from_instance is called in this case.

Steps to Reproduce

If I define a custom widget:

class MyWidget(s2forms.ModelSelect2Widget):
    model = MyModel
    queryset = MyModel.objects.all()
    
    def result_from_instance(self, obj, request):
        return {
            'id': obj.pk,
            'text': self.label_from_instance(obj),
            'my_extra': obj.extra_attribute,
        }

Then I define a form field with an initial value:

my_field = forms.ModelChoiceField(widget=MyWidget, initial=MyModel.objects.get(pk=123))

In JavaScript in the browser I look at the selected value with:

$('#id_my_field').select2('data')[0]

I expect to see attribute my_extra but it is not there, only id and text are. Once I select a different value from the options list, then my extra attribute shows up correctly.

Expected Behavior

I would expect that result_from_instance would be called and my extra attribute would be present when an unchanged default value is queried using $('#id_my_field').select2('data')[0]

[codingjoe]

Hi Thomas,

Thanks for reaching out. I am not sure, I fully understand your use case yet.
Let me try to explain how the package works. If you specify an initial value, the widget will render an action HTML option-tag. This tag will include a value and innerHtml.

In fact, this behavior can't easily be adapted. You see, result_from_instance gets the request passed from a view. However, Django's form framework, doesn't pass the request around.

That being said, there is always a way. Just not an easy one.

I hope this answer helps a little.

Cheers!
Joe

[tomas-nz]

Hi Joe,
Thank you for looking into this. I have two use cases:

1. I need to render different look for the selected item, and for options in the list. I do that by removing class "django-select2" and manual initialization in JavaScript, setting up templateSelection and templateResult. At the moment I override widget's label_from_instance returning something like "selection string" + <separator character> + "option string", and split this and use relevant portion in each function. I thought it would be more elegant to have these two parts returned from result_from_instance as separate attributes, rather than relying on special separator characters.
2. I need to transport additional attributes for a selected item to be used in my JavaScript code. There are two workarounds I can think of: Pack them into the label_from_instance result like above, or deliver them as separate attributes in result_from_instance, however for the initial value find a different way of delivery (put them somewhere on the form in a hidden field for example). Again, it would seem more elegant (code which is easier to read and maintain) if data produced by result_from_instance would be available for the initial value too.

If you think it is not achievable to change the behavior of result_from_instance for initial values, perhaps a note in the documentation explaining how this works would be useful. It could save someone new a bit of time working out these details.