Any media type starting with application/json treated as JSON

[scop]

Describe the bug

Any media type that starts with application/json is treated as JSON. This treatment should be limited to application/json and types with +json media type suffix. An example of a registered media type that triggers this problem is https://www.iana.org/assignments/media-types/application/json-seq

To Reproduce

PR #5895 has a failing test case.

Expected behavior

Not anything that begins with application/json should be treated as JSON.

Logs/tracebacks

-

Python Version

$ python --version
Python 3.9.6

aiohttp Version

$ python -m pip show aiohttp
WARNING: Package(s) not found: aiohttp

(current git master)

multidict Version

$ python -m pip show multidict
Name: multidict
Version: 5.1.0
Summary: multidict implementation
Home-page: https://github.com/aio-libs/multidict
Author: Andrew Svetlov
Author-email: andrew.svetlov@gmail.com
License: Apache 2
Location: /home/scop/.pyenv/versions/3.9.6/envs/aiohttp/lib/python3.9/site-packages
Requires: 
Required-by: yarl

yarl Version

$ python -m pip show yarl
Version: 1.6.3
Summary: Yet another URL library
Home-page: https://github.com/aio-libs/yarl/
Author: Andrew Svetlov
Author-email: andrew.svetlov@gmail.com
License: Apache 2
Location: /home/scop/.pyenv/versions/3.9.6/envs/aiohttp/lib/python3.9/site-packages
Requires: multidict, idna
Required-by:

OS

Any

Related component

Client

Additional context

No response

Code of Conduct

• I agree to follow the aio-libs Code of Conduct

[asvetlov]

Fixed by #5894

[scop]

As mentioned in #5895 (comment), this is a different thing, not fixed by #5894. The test case in #5895 still fails.

[scop]

Real fix in #6180.