Overriding APIView.get_renderers() does not automatically set Vary: Accept header

[PoByBolek]

One of my view classes overrides APIView.get_renderers() to return different renderers based on the inidividual view action, e.g. list() may use different renderers than retrieve() or update(). But it doesn't set the renderer_classes class attribute (because it doesn't need to anymore). Since renderer_classes still has its default value (and only contains a single value in my case), DRF doesn't set the Vary: Accept header for that view:

django-rest-framework/rest_framework/views.py

Lines 153 to 160 in 2510456

	@property
	def default_response_headers(self):
	headers = {
	'Allow': ', '.join(self.allowed_methods),
	}
	if len(self.renderer_classes) > 1:
	headers['Vary'] = 'Accept'
	return headers

Did I mess up here? Is APIView.get_renderers() considered a private API and am I supposed to only set renderer_classes? I mean, get_renderers() is at least mentioned on your documentation page... And there appear to be a few others who do this.

If not, would it be possible to add the Vary: Accept based on the result of get_renderers() instead of renderer_classes?

---

from restframework.views import APIView
from restframework.response import Response
from restframework.renderers import JSONRenderer, TemplateHTMLRenderer


class HasVaryAcceptHeader(APIView):
    renderer_classes = [JSONRenderer, TemplateHTMLRenderer]

    def get(self, *args, **kwargs):
        return Response()  # gets a Vary: Accept header

    def put(self, *args, **kwargs):
        return Response()  # gets a Vary: Accept header


class DoesNotHaveVaryAcceptHeader(APIView):
    def get(self, *args, **kwargs):
        return Response()  # *SHOULD* get a Vary: Accept header

    def put(self, *args, **kwargs):
        return Response()  # gets no Vary: Accept header

    def get_renderers():
        if self.request.method == 'GET':
            return [JSONRenderer(), TemplateHTMLRenderer()]
        else:
            return [JSONRenderer()]