Request json raises error if no arguments passed

[dmytrostriletskyi]

Long story short

The following code:

arguments = await request.json()
print(arguments)

Raises an exception:

[2018-09-29 11:42:33 +0000] [93] [ERROR] Error handling request
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/aiohttp/web_protocol.py", line 390, in start
    resp = await self._request_handler(request)
  File "/usr/local/lib/python3.6/site-packages/aiohttp/web_app.py", line 366, in _handle
    resp = await handler(request)
  File "/usr/local/lib/python3.6/site-packages/aiohttp/web_middlewares.py", line 106, in impl
    return await handler(request)
  File "/project/main/rest/middlewares/authorization.py", line 39, in auth_token_validation_middleware
    return await handler(request)
  File "/usr/local/lib/python3.6/site-packages/aiohttp/web_urldispatcher.py", line 740, in _iter
     resp = await method()
  File "/project/main/rest/endpoints/service/services/authentication/single.py", line 26, in put
    return await authentication.create_token(request=self.request)
  File "/project/main/core/service/services/authentication.py", line 99, in create_token
    arguments = await request.json()
  File "/usr/local/lib/python3.6/site-packages/aiohttp/web_request.py", line 551, in json
    return loads(body)
  File "/usr/local/lib/python3.6/json/__init__.py", line 354, in loads
    return _default_decoder.decode(s)
  File "/usr/local/lib/python3.6/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/local/lib/python3.6/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

After my http request without (!) PUT parameters:

http PUT :8000/some/endpoint

Expected behaviour

I expect, if length of request.text()equals 0, request.json() will return empty dictionary {} instead of raising.

Actual behaviour

While I pass parameter, my request.text() equals {"key": "value"} and request.json() equals {'key': 'value'}. When I do not pass parameter, JSONDecodeError is raised.

Steps to reproduce

from aiohttp import web


class SomeView(web.View):


    async def put(self):
        arguments = self.request.json()
        ...

Your environment

1. aiohttp (3.4.2)
2. Python 3.6
3. MacOs
4. Server

[aio-libs-bot]

GitMate.io thinks possibly related issues are #3242 (Error), #2174 (Insecure way to handle json requests), #2206 (json request for certain media types fail), #256 (More information provided when errors raised), and #2878 (Add argument 'raise_for_status' to 'ClientSession' request method.).

[asvetlov]

I disagree.
request.json() returns a JSON decoded payload.
An empty string is invalid JSON.
Raising an exception for invalid JSON sounds reasonable to me.

[dmytrostriletskyi]

@asvetlov, seems we consider the problem from different sides. Does aiohttp has simple features/ways to handle incoming arguments (if they are, we get dictionary, if not, if get something empty like {} without any exceptions) like request.POST in Django? Sorry for my bad knowledge of framework.

[asvetlov]

await request.post() returns an empty multidict if BODY doesn't exists but JSON is different.

[webknjaz]

I agree with Andrew. If body is empty, then it's an empty string, but you can't decode it as a JSON, because it's invalid.
OTOH you cannot choose a fallback, because it's app-specific and won't represent actual payload in any way. You expect dict, but someone else will expect list and I'll ask why not empty string then. See? It's overly ambiguous to try magically replace invalid input. And it's not a framework's job to do so.
If you need such a fallback you'll have to build your own helper for your app.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a [new issue] for related bugs.
If you feel like there's important points made in this discussion, please include those exceprts into that [new issue].
[new issue]: https://github.com/aio-libs/aiohttp/issues/new