"Unclosed client session" when initialization fails

[unights]

Describe the bug

This is actually a wrong use case.

Some parameters will be checked after the connection is established.

So the connection cannot be closed if there are incorrect parameters.

# -*- coding: utf-8 -*-
import asyncio

from aiohttp import ClientSession


async def main():
    async with ClientSession(timeout=1):
        pass


if __name__ == '__main__':
    asyncio.run(main())

How about deferring connection creation ( here ) ?

To Reproduce

as above

Expected behavior

First check that the parameters are correct and then establish the connection.

Logs/tracebacks

Traceback (most recent call last):
  File "D:\proj\test.py", line 13, in <module>
    asyncio.run(main())
  File "C:\Users\user\Miniconda3\Lib\asyncio\runners.py", line 190, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "C:\Users\user\Miniconda3\Lib\asyncio\runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\user\Miniconda3\Lib\asyncio\base_events.py", line 653, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "D:\proj\test.py", line 8, in main
    async with ClientSession(timeout=1):
               ^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\proj\.venv\Lib\site-packages\aiohttp\client.py", line 292, in __init__
    raise ValueError(
ValueError: timeout parameter cannot be of <class 'int'> type, please use 'timeout=ClientTimeout(...)'
Unclosed client session
client_session: <aiohttp.client.ClientSession object at 0x000001D74DC83CD0>

Python Version

$ python --version
Python 3.11.6

aiohttp Version

$ python -m pip show aiohttp
Name: aiohttp
Version: 3.9.3                                       
Summary: Async http client/server framework (asyncio)
Home-page: https://github.com/aio-libs/aiohttp       
Author:                                              
Author-email:
License: Apache 2
Location: D:\proj\.venv\Lib\site-packages
Requires: aiosignal, attrs, frozenlist, multidict, yarl
Required-by:

multidict Version

$ python -m pip show multidict
Name: multidict
Version: 6.0.5
Summary: multidict implementation
Home-page: https://github.com/aio-libs/multidict
Author: Andrew Svetlov
Author-email: [email protected]
License: Apache 2
Location: D:\proj\.venv\Lib\site-packages
Requires:
Required-by: aiohttp, yarl

yarl Version

$ python -m pip show yarl
Name: yarl
Version: 1.9.4
Summary: Yet another URL library
Home-page: https://github.com/aio-libs/yarl
Author: Andrew Svetlov
Author-email: [email protected]
License: Apache-2.0
Location: D:\proj\.venv\Lib\site-packages
Requires: idna, multidict
Required-by: aiohttp

OS

Windows 10

Related component

Client

Additional context

No response

Code of Conduct

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

[Dreamsorcerer]

Feel free to make a PR and move the check earlier.

[Dreamsorcerer]

Note that this solution doesn't help if you pass a connector in as an argument.