Impossible to return mime type other than application/json if multiple mime types are defined

[aigielsk]

We have an API spec in which we have a download operation that is supposed to return application/octet-stream (with status code 200). In case something is wrong with the user input another status codes are defined (400 and 404) that are supposed to return application/json.

This seems impossible to achieve with connexion. It always assumes application/json mime type and attempts to parse the JSON before sending the response.

Some details:
The method get_mimetype:

connexion/connexion/operations/abstract.py

Line 327 in ca70b16

def get_mimetype(self):

first checks if all returned mime types are the same and then (if this is not the case) - it only allows a non-JSON mime type if there is just one type defined:

connexion/connexion/operations/abstract.py

Lines 339 to 340 in ca70b16

	elif len(self.produces) == 1:
	return self.produces[0]

Otherwise it returns the DEFAULT_MIMETYPE, which is application/json.

It should be possible to define the returned mime type per returned status code.

[RobbeSneyders]

HI @aigielsk, handling multiple mimetypes on the same endpoint is indeed a current limitation of connexion (see #653). You can work around this by returning a response object with the correct mimetype set.

[RobbeSneyders]

Fixed in #1588