MultiPartParser throws a KeyError if parser_context is not provided

[biletboh]

If you try to use MultiPartParser without providing a request object in parser_context, it will throw a KeyError.

    def parse(self, stream, media_type=None, parser_context=None):
        """
        Parses the incoming bytestream as a multipart encoded form,
        and returns a DataAndFiles object.

        `.data` will be a `QueryDict` containing all the form parameters.
        `.files` will be a `QueryDict` containing all the form files.
        """
        parser_context = parser_context or {}
        request = parser_context['request']

It seems to be that parser_context is required and can't be None.

[itzzdev09]

Confirmed on DRF 3.18.0 — and parser_context={} fails the same way, so the or {} fallback doesn't actually save you:

>>> MultiPartParser().parse(io.BytesIO(b"x"), media_type="multipart/form-data; boundary=abc", parser_context=None)
KeyError: 'request'
>>> MultiPartParser().parse(io.BytesIO(b"x"), media_type="multipart/form-data; boundary=abc", parser_context={})
KeyError: 'request'

The reason it reads as optional is that the signature is shared across all parsers — JSONParser genuinely doesn't need it, while MultiPartParser needs the underlying request to hand to Django's own upload handling (encoding, upload_handlers, META). So parser_context is optional in the base signature but parser_context["request"] is effectively mandatory for this parser specifically.

In normal use you never hit this, because Request builds the context for you and always includes request. It only surfaces when calling a parser directly.

If you're calling it directly, pass a real request:

from rest_framework.test import APIRequestFactory

wsgi = APIRequestFactory().post("/", {"file": f}, format="multipart")
MultiPartParser().parse(wsgi, media_type=wsgi.content_type, parser_context={"request": wsgi})

Whether the fix should be a clearer TypeError explaining the requirement rather than a bare KeyError seems like the actual question here — the current failure gives no hint about what's missing.