keywords must be strings

[emmanuelito]

Python's JSON encoder allow integer as keys (and convert them as strings), but not flask-json.

>>> d = { 1 : "A" }
>>> json.dumps(d)
'{"1": "A"}'

>>> jsonify(d)
<Response 15 bytes [200 OK]>

>>> json_response(data_=d)
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/opt/scodoc/venv/lib/python3.9/site-packages/flask_json.py", line 145, in json_response
    response = jsonify(data_) if data_ is not None else jsonify(**kwargs)
TypeError: keywords must be strings

This is a problem when one wants to replace Flask's default JSON encoder by FlaskJSON.

[skozlovf]

@emmanuelito Sorry for the long response.
This happens because json_response() passes data_ as keyword arguments to the flask.jsonify().
But you don't need to use json_response() if you want to use FlaskJSON encoder - it's auto used by the flask.jsonify() if you initialized FlaskJSON. So this should work:

from flask import Flask
from flask import jsonify

app = Flask('xxx')
flask_json.FlaskJSON(app)
app.config['JSON_USE_ENCODE_METHODS'] = True

class MyJsonItem(object):
    def __json__(self):
        return '<__json__>'
    def for_json(self):
        return '<for_json>'

with app.test_request_context('/fake'):
    r = jsonify(MyJsonItem())
assert r.json == '<__json__>'

[emmanuelito]

@skozlovf thank you ! I understand now the source of the problem.
I was in fact using @as_json.
The point is that flask-json is not a drop-in replacement for regular Flask's jsonify, which can be annoying (maybe this detail should be stated in the doc?).

[skozlovf]

@emmanuelito

maybe this detail should be stated in the doc?

I'll think about it. I planned to update internals to follow new Flask 2.3 API and will improve stuff to handle this case. Let's keep the issue open.
Thanks.

[skozlovf]

Fixed/improved in 0.4.0.