Fixed #9161 -- Ensure that ModelMultipleChoiceField respects to_field_name in...

            return []

        if not isinstance(value, (list, tuple)):

            raise ValidationError(self.error_messages['list'])

        key = self.to_field_name or 'pk'

        for pk in value:

            try:

                self.queryset.filter(pk=pk)

                self.queryset.filter(**{key: pk})

            except ValueError:

                raise ValidationError(self.error_messages['invalid_pk_value'] % pk)

        qs = self.queryset.filter(pk__in=value)

        pks = set([force_unicode(o.pk) for o in qs])

        qs = self.queryset.filter(**{'%s__in' % key: value})

        pks = set([force_unicode(getattr(o, key)) for o in qs])

        for val in value:

            if force_unicode(val) not in pks:

                raise ValidationError(self.error_messages['invalid_choice'] % val)

<tr><th><label for="id_description">Description:</label></th><td><input type="text" name="description" id="id_description" /></td></tr>

<tr><th><label for="id_url">The URL:</label></th><td><input id="id_url" type="text" name="url" maxlength="40" /></td></tr>

# to_field_name should also work on ModelMultipleChoiceField ##################

>>> field = ModelMultipleChoiceField(Inventory.objects.all(), to_field_name='barcode')

>>> for choice in field.choices:

...     print choice

(86, u'Apple')

(22, u'Pear')

(87, u'Core')

>>> field.clean([86])

[<Inventory: Apple>]

>>> class SelectInventoryForm(forms.Form):

...     items = ModelMultipleChoiceField(Inventory.objects.all(), to_field_name='barcode')

>>> form = SelectInventoryForm({'items': [87, 22]})

>>> form.is_valid()

True

>>> form.cleaned_data

{'items': [<Inventory: Pear>, <Inventory: Core>]}

# Model field that returns None to exclude itself with explicit fields ########

>>> class CustomFieldForExclusionForm(ModelForm):