RuntimeError: no running event loop

[tomplus]

Describe the bug

It looks like a breaking change in the latest version.

In version 3.9.5 it works:

import aiohttp
connector = aiohttp.TCPConnector()

(in a more complex example I get a warning (DeprecationWarning: The object should be created within an async function))

but in 3.10 I get an exception:

Traceback (most recent call last):
  File "/tmp/a1.py", line 5, in <module>
    connector = aiohttp.TCPConnector()
  File "/home/tomek/work/github/kubernetes-client/kubernetes_asyncio-new/VENV/lib/python3.10/site-packages/aiohttp/connector.py", line 784, in __init__
    super().__init__(
  File "/home/tomek/work/github/kubernetes-client/kubernetes_asyncio-new/VENV/lib/python3.10/site-packages/aiohttp/connector.py", line 234, in __init__
    loop = loop or asyncio.get_running_loop()
RuntimeError: no running event loop

To Reproduce

code

import aiohttp
connector = aiohttp.TCPConnector()

Expected behavior

If the change is intentional it would be very useful to describe that in a changelog.
If not I expect the same behavior like in the previous version.

Logs/tracebacks

Traceback (most recent call last):
  File "/tmp/a1.py", line 5, in <module>
    connector = aiohttp.TCPConnector()
  File "/home/tomek/work/github/kubernetes-client/kubernetes_asyncio-new/VENV/lib/python3.10/site-packages/aiohttp/connector.py", line 784, in __init__
    super().__init__(
  File "/home/tomek/work/github/kubernetes-client/kubernetes_asyncio-new/VENV/lib/python3.10/site-packages/aiohttp/connector.py", line 234, in __init__
    loop = loop or asyncio.get_running_loop()
RuntimeError: no running event loop

### Python Version

```console
$ python --version
3.10

aiohttp Version

$ python -m pip show aiohttp
Name: aiohttp
Version: 3.10.0

multidict Version

$ python -m pip show multidict
Name: multidict
Version: 6.0.4

yarl Version

$ python -m pip show yarl
Name: yarl
Version: 1.8.2

OS

Linux

Related component

Client

Additional context

No response

Code of Conduct

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

[bdraco]

It looks like this is caused by #8512 which is a backport of #5278 from master

[bdraco]

It looks like it was deprecated in 3.9.5 and now no longer works in 3.10.0 https://github.com/aio-libs/aiohttp/blob/3.9/aiohttp/helpers.py#L296 but #5278 didn't have a changelog message to say it would stop working.

In 3.9.5 it would create a new non-running event loop

>>> import aiohttp
>>> print(aiohttp.__version__)
3.9.5
>>> connector = aiohttp.TCPConnector()
>>> print(connector._loop)
<_UnixSelectorEventLoop running=False closed=False debug=False>
>>> 

[bdraco]

Based on the above, I'd say the change is intentional but could use a changelog entry.

[bdraco]

Creating a ClientSession, CookieJar, or Connector without a running asyncio event loop will now explicitly raise in 3.10.0 because it calls asyncio.get_running_loop()

[aslonnie]

is this going to be fixed in 3.10.1 ? or is this breakage intentional?

[bdraco]

The only planned change is to improve the changelog. As it was deprecated over 5 years ago, there is no plan to extend the deprecation period.

Edit: This practice is deprecated in Python as well

https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.get_event_loop

[TheDurableDane]

This is a breaking change (intentional or not), so shouldn't the version be bumped to 4.0.0? Regardless of the length of the deprecation period.

[webknjaz]

https://hynek.me/articles/semver-will-not-save-you/#taking-responsibility