'try-except-raise' warnings on 3.9 but not 3.7

[RemiCardona]

Bug description

import asyncio

async def coro():
    try:
        await asyncio.sleep(0.5)
    except asyncio.CancelledError:
        raise
    except ValueError:
        pass

No warning raised when running in a python 3.7 venv, W0706(try-except-raise) warning raised with an identical pylint call when running in a 3.9 venv.

# pylint: disable=try-except-raise,useless-suppression thus needed to make pylint happy on both 3.7 and 3.9.

Configuration

No response

Command used

pylint demo.py

Pylint output

************* Module bluelink.demo
demo.py:7: [W0706(try-except-raise), coro] The except handler raises immediately

Expected behavior

No warning raised, as on 3.7. It's a false positive.

Pylint version

pylint 2.12.2
astroid 2.9.3
Python 3.7.12 (default, Mar  8 2022, 11:09:12) 
[GCC 11.2.1 20220115]

and

pylint 2.12.2
astroid 2.9.3
Python 3.9.10 (main, Mar  8 2022, 11:00:59) 
[GCC 11.2.1 20220115]

OS / Environment

~amd64 Gentoo (outputs above) and Debian Buster (with different python patch-level versions)

Additional dependencies

No response

[Pierre-Sassoulas]

Thank you for opening the issue. Are you using the py-version option (set to 3.7) ?

[RemiCardona]

Nope, I'm not using this option. And I can reproduce the bug with the provided sample and a plain call to pylint demo.py.

[Pierre-Sassoulas]

Sorry it was unclear. I was asking that because it's the official way to make pylint run on multiple python interpreters (so you get 3.7 errors even when using pylint with python 3.9), you should always use the lowest interpreter you support in this case 3.7. Could you try it ? It's entirely possible that it's still a bug because we added this option recently.

[RemiCardona]

I tried setting py-version to both 3.7 and 3.9, under both venvs and the results are the same as before.

[jacobtylerwalls]

Thanks for writing. This is a false negative for try-except-raise in python 3.7. The warning is emitted correctly on Python 3.9.

Most likely, the failure to raise on Python 3.7 is because before Python 3.8 asyncio.CancelledError had a more complicated inheritance structure (it just aliased concurrent.futures.CancelledError). See also: #3083 (comment).

Ultimately, this is just a failure to infer asyncio.CancelledError in python 3.7:

(Pdb) handler.type
<Attribute.CancelledError l.6 at 0x7fc4709ced90>
(Pdb) utils.safe_infer(handler.type)
Uninferable

Python 3.7 source, showing why it may be hard to infer this correctly:
https://github.com/python/cpython/blob/f656bc1cdbdfaaa07f66ed97e011b258b97e2788/Lib/asyncio/base_futures.py#L3-L9

I don't know that there's much we can do about this in astroid. I think you've found the best workaround.