How to customise FILTER_DEFAULTS (e.g. for FileField)

[clement-escolano]

When using django-filter with Django-Rest-Framework, I was confused because I could not use django-filter to filter on a FileField (I know the path of the file and want to get the item that has this file). When setting up a filter on a FileField, the following error occurs:

AssertionError: QuestionnaireFilter resolved field 'file' with 'exact' lookup to an unrecognized field type FileField. Try adding an override to 'Meta.filter_overrides'. See: https://django-filter.readthedocs.io/en/main/ref/filterset.html#customise-filter-generation-with-filter-overrides

Code details

class Questionnaire(models.Model):
    file = models.FileField(upload_to=questionnaire_path)

class QuestionnaireFilter(FilterSet):
    class Meta:
        model = Questionnaire
        fields = ['file']

class QuestionnaireViewset(viewsets.ModelViewSet):
    filterset_class = QuestionnaireFilter

I am confused because this seems a common use case and could not find any information about it except adding filter_overrides for every FilterSet I need.

Code details with filter_overrides

class QuestionnaireFilter(FilterSet):
    class Meta:
        model = Questionnaire
        fields = ['file']
        filter_overrides = {
            models.FileField: {
                'filter_class': CharFilter,
                'extra': lambda f: {'lookup_expr': 'exact'},
            },
        }

Is this on purpose to not support the `FileField`? Is there some way to make this filter_overrides globally to avoid adding it in a lot of filter sets?

Thank you and have a good day

[carltongibson]

Hi @clement-escolano.

There's no FileFilter.

Is there some way to make this filter_overrides globally to avoid adding it in a lot of filter sets?

You can declare a base FilterSet subclass for your project. Inheritance of internal Meta classes gets sticky, so adjusting FILTER_DEFAULTS is likely the way to go. See how the rest_framework.FilterSet class does it:

django-filter/django_filters/rest_framework/filterset.py

Lines 17 to 25 in c906cf3

	FILTER_FOR_DBFIELD_DEFAULTS = deepcopy(filterset.FILTER_FOR_DBFIELD_DEFAULTS)
	FILTER_FOR_DBFIELD_DEFAULTS.update({
	models.DateTimeField: {'filter_class': IsoDateTimeFilter},
	models.BooleanField: {'filter_class': BooleanFilter},
	})
	class FilterSet(filterset.FilterSet):
	FILTER_DEFAULTS = FILTER_FOR_DBFIELD_DEFAULTS

I hope that helps.

[clement-escolano]

Alright thank you! I will follow the same pattern

[clement-escolano]

Out of curiosity, why there is no default filter for FileField?