Can't find swagger.json when using sanic-openapi

Question

I'm trying to use Sanic-OpenAPI module with sanic to auto-document my own RESTful APIs. So, I installed them by running the following command:

pip install sanic sanic-openapi

# sanic version is 19.12.2
# sanic_openapi version is 0.6.1

And I created this simple project which is, by the way, provided in their official GitHub repository. And it looks like the following:

from sanic import Sanic, response
from sanic_openapi import swagger_blueprint


app = Sanic("app")
app.blueprint(swagger_blueprint)


@app.route("/")
async def test(request):
    return response.json({"hello": "world"})


if __name__ == "__main__":
    app.run(host="0.0.0.0", port=8000, debug=True)

This runs just fine! But when I try to access the http://localhost:8000/swagger, it throws the following error:

Traceback (most recent call last):
  File "/media/anwar/E/Chatbot/NLU_engine/py3.7/lib/python3.7/site-packages/sanic/app.py", line 974, in handle_request
    response = handler(request, *args, **kwargs)
  File "/media/anwar/E/Chatbot/NLU_engine/py3.7/lib/python3.7/site-packages/sanic_openapi/swagger.py", line 263, in spec
    return json(swagger_blueprint._spec)
  File "/media/anwar/E/Chatbot/NLU_engine/py3.7/lib/python3.7/site-packages/sanic/response.py", line 234, in json
    dumps(body, **kwargs),
TypeError: <sanic_openapi.spec.Spec object at 0x7effe3d2f910> is not JSON serializable
[2020-07-12 11:34:09 +0200] - (sanic.access)[INFO][127.0.0.1:37880]: GET http://localhost:8000/swagger/swagger.json  500 2649
[2020-07-12 11:34:09 +0200] [11014] [ERROR] Exception occurred while handling uri: 'http://localhost:8000/swagger/swagger.json'
Traceback (most recent call last):
  File "/media/anwar/E/Chatbot/NLU_engine/py3.7/lib/python3.7/site-packages/sanic/app.py", line 974, in handle_request
    response = handler(request, *args, **kwargs)
  File "/media/anwar/E/Chatbot/NLU_engine/py3.7/lib/python3.7/site-packages/sanic_openapi/swagger.py", line 263, in spec
    return json(swagger_blueprint._spec)
  File "/media/anwar/E/Chatbot/NLU_engine/py3.7/lib/python3.7/site-packages/sanic/response.py", line 234, in json
    dumps(body, **kwargs),
TypeError: <sanic_openapi.spec.Spec object at 0x7effe3d2f910> is not JSON serializable

Answer 1

After around two hours of searching, I've found out the solution in this issue on their official GitHub repository. The reason, according to the issue, is that sanic-openapi is not compatible with the last two releases (2.x and 3.x) of ujson.

So, to fix this issue, you need to downgrade your ujson package to 1.35 like so:

pip install ujson==1.35

And it works perfectly now: