New submission from Ron Frederick <[email protected]>:
In testing AsyncSSH against Python 3.8, I noticed a large number of the
following errors, even though I was properly closing streams before the objects
holding them were garbage-collected.
An open stream object is being garbage collected; call "stream.close()"
explicitly.
After some investigation, the problem appears to be that closing a stream is
not good enough to prevent the error. The check in asyncio doesn't properly
handle the case where the stream is closing, but has not fully closed. Here's a
simple test program that demonstrates this:
import asyncio
async def tcp_client():
reader, writer = await asyncio.open_connection('127.0.0.1', 22)
writer.close()
asyncio.run(tcp_client())
It's possible to avoid this message by awaiting on writer.wait_closed(), but
wait_closed() doesn't exist until Python 3.7, making it very difficult to write
portable code and still avoid this message.
----------
components: asyncio
messages: 354953
nosy: Ron Frederick, asvetlov, yselivanov
priority: normal
severity: normal
status: open
title: Python 3.8 improperly warns about closing properly closed streams
type: behavior
versions: Python 3.8
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Python tracker <[email protected]>
<https://bugs.python.org/issue38529>
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