Add support for different content type responses (e.g. application/octet-stream)

[LevonW-IIS]

I have been creating a ninja API for my web app and have found the process very smooth, and have been enjoying the open API auto documentation, which I rely on in my front-end. I have encountered one problem in dealing with a file download endpoint.

The response should be easily specifiable under the openapi specs as

content:
  application/octet-stream:
    schema:
      type: string
      format: binary

however I've found no easy way to implement this within django-ninja.

I've had a look through the code and I think I've found where a change could be made

if model not in [None, NOT_SET]:
    # ::TODO:: test this: by_alias == True
    schema = self._create_schema_from_model(
        model, by_alias=operation.by_alias
    )[0]
    details[status]["content"] = {
        self.api.renderer.media_type: {"schema": schema}
    }

if the schema had an __ninja_override_media_type__ attribute, this could be used to provide a custom media type for a response.

If you want me to have a stab at writing a PR for this let me know

[vitalik]

Hi @LevonW-IIS

currently you can do it like this:

BIN_RESPONSE = {
    "responses": {
        200: {
            "description": "OK",
            "content": {"application/octet-stream": {"schema": {"type": "string", "format": "binary"}}},
        }
    }
}


@api.get("/hello", openapi_extra=BIN_RESPONSE)
def hello(request):
    return HttpResponse(b'hello', content_type='application/octet-stream')

but yeah - I guess some nicer/less-wordy solution would be nice...

like maybe this should give the same result:

@api.get("/hello", response=bytes)
def hello(request):
    return b'hello'

but maybe it's not super obvious.. not sure yet - still thinking

[LevonW-IIS]

Thanks for the speedy reply. Didn't manage to spot this in the docs.

Some extension of response= would be nice. There's a fair few file types where "schema": {"type": "string", "format": "binary"} would remain the same but you might want to change up the content type, e.g. application/pdf, application/zip, application/vnd.*.

Would be quite nice to use something like:

@api.get("/hello", response=BytesResponse("application/pdf"))
def hello(request):
    file_content: bytes = get_file_content()
    return file_content

[andy-isoc]

class CsvRenderer(BaseRenderer):

    def render(self, request, data, *, response_status):
        # Ignore if the data is already an HttpResponse here as that allows us to override the csv rendering per endpoint
        if request.headers.get('Accept') == 'text/csv' and not isinstance(data, HttpResponse):
            csv_data = render_csv(data)
            self.media_type = "text/csv"
            return HttpResponse(csv_data, status=200, content_type="text/csv")
        else:
            self.media_type = "application/json"
            return json_renderer.render(request, data, response_status=response_status)

It seems the problem in our case is with the temporal_response which sets the Content-type from the Renderer before render() is called.

[andy-isoc]

I guess using a Renderer for this is a bit of a hack but I couldn't see a better way to do it. We could set the Content-type manually on the temporal_response as well I suppose.

[andy-isoc]

Ok, figured it out

class CsvRenderer(BaseRenderer):
    media_type = "application/json"

    def render(self, request, data, *, response_status):
        if request.headers.get("Accept") == "text/csv":
            csv_data = render_csv(data)
            return HttpResponse(csv_data, status=200, content_type="text/csv")
        else:
            return json_renderer.render(request, data, response_status=response_status)

Plus on our API class

    def create_temporal_response(self, request: HttpRequest) -> HttpResponse:
        if request.headers.get("Accept") == "text/csv":
            return HttpResponse("", content_type="text/csv; charset=utf-8")
        return super().create_temporal_response(request)

That seems to work ok now.