asyncio subprocess spawn does not record the awaiting task

Inizia in Lib/asyncio/base_subprocess.py, all’interno di BaseSubprocessTransport.init, e analizza il percorso di connessione della pipe del sottoprocesso mostrato nel traceback. Esegui la riproduzione asyncio fornita e verifica che l’attività interna di connessione della pipe segnali un arco “Awaited by” per l’attività di spawn, quindi verifica che l’arco venga scartato dal callback di completamento.

Bug report

Bug description:

The internal subprocess pipe-connect task registers no awaited_by edge

Repro:

import asyncio, sys

async def main():
    spawn = asyncio.create_task(
        asyncio.create_subprocess_exec(sys.executable, '-c', 'pass',
                                       stdin=asyncio.subprocess.PIPE),
        name='spawn')

    await asyncio.sleep(0)
    await asyncio.sleep(0)

    for t in asyncio.all_tasks() - {asyncio.current_task()}:
        asyncio.print_call_graph(t)

    proc = await spawn
    await proc.wait()

asyncio.run(main())

Actual:

* Task(name='spawn', id=0x103e00b90)
  + Call stack:
  |   File '/Users/timofeiivankov/cpython/Lib/asyncio/unix_events.py', line 211, in async _UnixSelectorEventLoop._make_subprocess_transport()
  |   File '/Users/timofeiivankov/cpython/Lib/asyncio/base_events.py', line 1839, in async BaseEventLoop.subprocess_exec()
  |   File '/Users/timofeiivankov/cpython/Lib/asyncio/subprocess.py', line 249, in async create_subprocess_exec()
* Task(name='Task-2', id=0x103b7d0a0)
  + Call stack:
  |   File '/Users/timofeiivankov/cpython/Lib/asyncio/base_events.py', line 1753, in async BaseEventLoop.connect_write_pipe()
  |   File '/Users/timofeiivankov/cpython/Lib/asyncio/base_subprocess.py', line 188, in async BaseSubprocessTransport._connect_pipes()

Expected:

* Task(name='spawn', id=0x105620b90)
  + Call stack:
  |   File '/Users/timofeiivankov/cpython/Lib/asyncio/unix_events.py', line 211, in async _UnixSelectorEventLoop._make_subprocess_transport()
  |   File '/Users/timofeiivankov/cpython/Lib/asyncio/base_events.py', line 1839, in async BaseEventLoop.subprocess_exec()
  |   File '/Users/timofeiivankov/cpython/Lib/asyncio/subprocess.py', line 249, in async create_subprocess_exec()
* Task(name='Task-2', id=0x10539d0a0)
  + Call stack:
  |   File '/Users/timofeiivankov/cpython/Lib/asyncio/base_events.py', line 1753, in async BaseEventLoop.connect_write_pipe()
  |   File '/Users/timofeiivankov/cpython/Lib/asyncio/base_subprocess.py', line 194, in async BaseSubprocessTransport._connect_pipes()
  + Awaited by:
    * Task(name='spawn', id=0x105620b90)
      + Call stack:
      |   File '/Users/timofeiivankov/cpython/Lib/asyncio/unix_events.py', line 211, in async _UnixSelectorEventLoop._make_subprocess_transport()
      |   File '/Users/timofeiivankov/cpython/Lib/asyncio/base_events.py', line 1839, in async BaseEventLoop.subprocess_exec()
      |   File '/Users/timofeiivankov/cpython/Lib/asyncio/subprocess.py', line 249, in async create_subprocess_exec()

Proposed fix: register the edge in BaseSubprocessTransport.__init__ and discard it in doe callback

I have a fix ready for that

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS