jsonify_data is called on ConnexionResponse regardless of mimetype/content_type

[ASVincent]

Description

I wish to return data through a swagger endpoint that is not json serialised (text/plain); the documents suggest that this could be accomplished by initialising and returning a ConnexionResponse instance.

The purpose of this is to return metrics information for prometheus without adding additional middleware or a separate process to handle it.

Expected behaviour

The connexion documentation (https://connexion.readthedocs.io/en/latest/response.html) states that:

One way is to return a Response object that will be used unchanged.

def get_healthcheck()
    return ConnexionResponse(content_type='text/plain', body=b'hello-world')

Should return hello-world

Actual behaviour

TypeError: Object of type bytes is not JSON serializable

This occurs because cls._jsonify_data is applied regardless of the parameterisation of ConnexionResponse.

In connexion/apis/flask_api.py:182..184

        if data is not None and data is not NoContent:
            data = cls._jsonify_data(data, mimetype)
            flask_response.set_data(data)

Steps to reproduce

See expected behaviour for an endpoint that based on the documentation should be return without error.

Additional info:

Output of the commands:

• python --version
  Python 3.7.4
• pip show connexion | grep "^Version\:"
  Version: 2.3.0

[hjacobs]

Thanks for reporting! As a current workaround you could define the path on the Flask app directly.

[dtkav]

Can you post your openapi spec?

While Connexion does has some major problems with handling multiple content types on a single endpoint (I've done some work on this #760 here), if your endpoint explicitly (and only) returns 'text/plain' in your spec, it should work fine.