Add test for #25980: ModelMultipleChoiceField does not properly clean QuerySets

[karyon]

See https://code.djangoproject.com/ticket/25980

[timgraham]

"used to" in an older version of Django? Did you find the commit where the behavior changed?

[karyon]

eh sorry, so that fails right now, with the current 1.9.x branch. i don't know when it got introduced, i can search for that if you want. i guess this got exposed with the introduction of the disabled attribute, as with it the initial value is passed unprocessed into clean.

[karyon]

the clean method seems to handle only lists and tuples of PKs and false-y values since it was created (somewhere in 2007).

[timgraham]

Can you give a higher level example? I tested with a form like this and didn't encounter any problems:

class Form(forms.ModelForm):
    choices = forms.ModelMultipleChoiceField(queryset=Choice.objects.all(), disabled=True, required=False)

    class Meta:
        model = Question
        fields = '__all__'

[karyon]

you have to provide an initial value that is not False-y. this will be passed to the clean method as-is on disabled fields, which i simulated in the test. i can provide a test using a complete form later.

[timgraham]

I tested with a Question which had an existing many-to-many relation for choices, but I think I understand the problem now. You passed a queryset as the form's initial value. The documentation says, "Validates that every id in the given list of values exists in the queryset." so I think you should be providing a list of ids for the initial values instead of a queryset.

[timgraham]

Closing since this test isn't meant to merged.