How to natively handle multiple values for one parameter name separated by ampersand? #1736

arpit-nectar · 2025-11-26T22:31:13Z

arpit-nectar
Nov 26, 2025

Hi, I'm trying to build some filters where we pass multiple values for one parameter name. I was hoping to represent the values in the query string as follows foo=1&foo=2, instead of foo=1,2. This is because my values themselves could have commas in them. I assumed that there would be a filter that natively supports this strategy, but BaseInFilter was not working.

I traced through the code and found that BaseInFilter uses BaseCSVFilter, which uses BaseCSVField as the base_field_class, which in turn uses the BaseCSVWidget. I saw that BaseCSVWidget had behavior I would expect to process the values, i.e.

    def value_from_datadict(self, data, files, name):
        value = super().value_from_datadict(data, files, name)

        if value is not None:
            if value == "":  # empty value should parse as an empty list
                return []
            if isinstance(value, list):
                # since django.forms.widgets.SelectMultiple tries to use getlist
                # if available, we should return value if it's already an array
                return value
            return value.split(",")
        return None

However, since it inherits from forms.Widget, the value_from_datadict function will always use data.get instead of every trying data.getlist. So even though the query params in the QueryDict will be a list, .get will only get one element from the list. I was wondering if this is expected behavior, or if there is a better Widget to inherit from, or a different Filter I should be using.