[FIXED] Invisible keyword arguments in flask GET operation cause TypeError

Issue

I have a very simple GET handler in flask that looks like this:

@app.route('/thing/<thing_id>', methods=['GET'])
def get_thing(thing_id):
    """Get thing"""
    json_in = {
       "id": thing_id
    }
    return jsonify(app.thing_service.on_get_thing(json_in))

which is very simple, and complies with all the documentation for Flask. It works locally. However, when I push it to the server, it fails with the message:

TypeError: get_thing() takes no keyword arguments

which sounds like get_thing is being passed some extra argument, but only on the server. If I account for these mysterious extra arguments that should not exist, it works, but there appear to be no arguments:

@app.route('/thing/<thing_id>', methods=['GET'])
def get_thing(thing_id, *args, **kwargs):
    """Get thing"""
    logger.info(f'args: {args}')
    logger.info(f'kwargs: {kwargs}')
    json_in = {
       "id": thing_id
    }
    return jsonify(app.thing_service.on_get_thing(json_in))

produces args: () and kwargs: {} in the logs. But with this in place, the endpoint works. What could be causing this to happen?

The full traceback for the error:

Traceback (most recent call last):
  File ".../python3.7/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
      File ".../python3.7/site-packages/flask/app.py", line 1936, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
TypeError: get_thing() takes no keyword arguments

Solution

The answer is found here: Flask url with only one parameter is not processed

My code is cythonized as part of the CICD process. The local code is not. In the call to cythonize, the compiler directive always_allow_keywords must be set to True.

Answered By - Fadecomic