all deprecation warnings are disabled for the whole process while new unix asyncio subprocesses are created

[graingert]

on python3.10 the following prints:

python3.10 demo.py 
/home/graingert/projects/cpython/demo.py:40: DeprecationWarning: demo warning
 warnings.warn("demo warning", DeprecationWarning)
/home/graingert/projects/cpython/demo.py:48: DeprecationWarning: demo warning2
 warnings.warn("demo warning2", DeprecationWarning)

but on python main it prints:

./python demo.py 
/home/graingert/projects/cpython/demo.py:40: DeprecationWarning: demo warning
 warnings.warn("demo warning", DeprecationWarning)

import sys
import threading
import asyncio
import concurrent.futures
import warnings


async def acreate_process_then_sleep(started_event, stop_event):
 event = asyncio.Event()

 async def create_process():
 loop = asyncio.get_running_loop()
 loop.call_soon(event.set)
 proc = await asyncio.create_subprocess_exec(
 sys.executable,
 "-c",
 "print('hello')",
 stdin=None,
 stdout=asyncio.subprocess.PIPE,
 stderr=asyncio.subprocess.STDOUT,
 )
 await proc.communicate()

 async def sleep():
 await event.wait()
 started_event.set()
 stop_event.wait()

 await asyncio.gather(create_process(), sleep())


def create_process_then_sleep(*args, **kwargs):
 asyncio.run(acreate_process_then_sleep(*args, **kwargs))


def main():
 with concurrent.futures.ThreadPoolExecutor() as tpe:
 stop_event = threading.Event()
 started_event = threading.Event()
 warnings.warn("demo warning", DeprecationWarning)
 fut = tpe.submit(
 create_process_then_sleep,
 started_event=started_event,
 stop_event=stop_event,
 )
 try:
 started_event.wait()
 warnings.warn("demo warning2", DeprecationWarning)
 finally:
 stop_event.set()
 fut.result()


if __name__ == "__main__":
 sys.exit(main())

Originally posted by @graingert in #98215 (comment)

[graingert]

cc @kumaraditya303

[graingert]

see also #91505, #81785 and #50896

[kumaraditya303]

Okay, I'll be AFK for some time so feel free to create a PR. I doubt that any one will hit this in practise though.

[gvanrossum]

Ah, I guess I was right about that context manager. :-)

[kumaraditya303]

#98333 fixes this, I had underestimated warnings module :-)

[gvanrossum]

We're still looking for a perfect solution (see discussion in PR), so keeping this issue open.