JSONRenderer does not return a valid json response when data=None

[kltdwrds]

Steps to reproduce

@permission_classes((AllowAny, ))
class Viewset(viewsets.ViewSet):
    renderer_classes = (JSONRenderer, )
    def list(self, request, *args, **kwargs):
        return Response()

Expected behavior

A valid json response body like null or {}

Actual behavior

No Content-Type header set and an empty response is returned - particularly painful when making requests with jquery's ajax(). It throws an parseerror and rejects the promise on a success response with an empty body. See here https://stackoverflow.com/a/6186905

PR here: #6027

[rpkilby]

Just a quick clarification.. I may not be recreating your exact setup, but a quick, manual test shows that the Content-Type header is correctly set to application/json.

As to the empty response, I'm inclined to agree with @kltdwrds. I don't know if the spec allows an empty body, however, both JavaScript's JSON.parse and Python's json.loads fail to decode an empty string.

That is to say, data=None should be encoded as null.

---

On second thought, the current behavior makes sense. Although JSON.parse and json.loads do fail, it's the responsibility of the client to check the content type before parsing. If anything, this is a bug in jQuery.

[kltdwrds]

hmm I'm using

from rest_framework import viewsets
from rest_framework.renderers import JSONRenderer
from rest_framework.response import Response

Not sure where the Content-Type header gets set, but I just confirmed it missing from responses using the example above.

[kltdwrds]

It looks like the Content-Type header is deleted on an empty renderer response (line 80)
https://github.com/encode/django-rest-framework/blob/master/rest_framework/response.py#L72

[tomchristie]

Our current behavior for return Response() is intentional. Although returning null would also be valid, it's more typical that we need a way to return an empty response with no content type. I'd probably rather we leave things as they are for now.