The full example needs a few notes on usage and RestX needs to fail on JSON parsing

[jkugler]

EDIT: This was originally entitled "Full example does not work, and I can't figure out why." Digging in, I discovered the reason, as seen in the two following comments.

Code

The code I'm using is here: https://flask-restx.readthedocs.io/en/latest/example.html Copied and pasted it. The only change I made was to run the debug server on 8080.

Repro Steps (if applicable)

1. python3 example.py
2. Ran curl http://localhost:8080/todos/. That printed out the ones already created
3. Ran curl http://localhost:8080/todos/ -d "data=Remember the milk" -X POST

Expected Behavior

I expected a Todo to be created

Actual Behavior

127.0.0.1 - - [04/Nov/2020 14:22:29] "GET /todos/ HTTP/1.1" 200 -
[2020-11-04 14:23:31,567] ERROR in app: Exception on /todos/ [POST]
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/flask/app.py", line 1949, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/lib/python3/dist-packages/flask/app.py", line 1935, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/usr/local/lib/python3.8/dist-packages/flask_restx/api.py", line 375, in wrapper
    resp = resource(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/flask/views.py", line 89, in view
    return self.dispatch_request(*args, **kwargs)
  File "/usr/local/lib/python3.8/dist-packages/flask_restx/resource.py", line 44, in dispatch_request
    resp = meth(*args, **kwargs)
  File "/usr/local/lib/python3.8/dist-packages/flask_restx/marshalling.py", line 248, in wrapper
    resp = f(*args, **kwargs)
  File "/home/jkugler/app/example.py", line 66, in post
    return DAO.create(api.payload), 201
  File "/home/jkugler/app/example.py", line 32, in create
    todo['id'] = self.counter = self.counter + 1
TypeError: 'NoneType' object does not support item assignment

Debugging uncovered that the data passed to def create(self, data) was None which means api.payload here:

    def post(self):
        '''Create a new task'''
        return DAO.create(api.payload), 201

is None. I have no idea why. I've dumped requeset headers, as well as the contentx of the wsgi.input object, and everything is there.

Error Messages/Stack Trace

See above.

Environment

• Python version: Python 3.8.6
• Flask version: 1.1.1
• Flask-RESTX version: 0.2.0
• Other installed Flask extensions

Flask-BabelEx                 0.9.3               
Flask-Compress                1.4.0               
Flask-Gravatar                0.4.2               
Flask-Login                   0.4.1               
Flask-Mail                    0.9.1               
Flask-Migrate                 2.5.2               
Flask-Paranoid                0.2.0               
Flask-Principal               0.4.0               
Flask-Security                1.7.5               
Flask-SQLAlchemy              2.1                 
Flask-WTF                     0.14.2

[jkugler]

FYI, same errant behavior if I do curl http://localhost:8080/todos/ -d "task=Remember the milk" -X POST (use 'task' instead of 'data').

[jkugler]

Well, I'm figuring this out. The examples here: https://flask-restx.readthedocs.io/en/latest/quickstart.html show the use of curl http://localhost:5000/todo1 -d "data=Remember the milk" -X PUT. The "Full Example" page does not provide any guidance that might indicate it is different. However, it seems it is requiring JSON input.

https://github.com/python-restx/flask-restx/blob/master/flask_restx/api.py#L784 calls request.get_json() with all the defaults: force=False, silent=False, cache=True which in turns activates this:

        if not (force or self.is_json):
            return None

which returns None without comment or error.

i would suggest a couple things:

1. Add some example calling code to the Full Example to show how it should be used from curl. This works:

curl http://localhost:8080/todos/ -H "Content-Type: application/json" -d '{"task": "Remember the milk"}' -X POST

2. Raise an error in Api.payload when there is an error decoding the request. Api.payload is obviously expecting a JSON request, so it should error if it doesn't get it. Calling get_json(force=True, silent=False, cache=False). That will raise BadRequest("Failed to decode JSON object: {0}".format(e)) which would be the best, most unambiguous thing to do because "None" could have been a valid JSON object:

>>> import json
>>> json.dumps(None)
'null'
>>> json.loads('null')
>>>

[ProgHaj]

I agree with the above suggestions, and added them to a PR. The second will provide some breaking functionality for users, so I suggest it be part of a major release if possible.