[3.12] GH-106684: Close asyncio.StreamWriter when asyncio.StreamWriter is not closed by application (GH-107650)

[miss-islington]

(cherry picked from commit 41178e4)

Co-authored-by: Kumar Aditya kumaraditya@python.org

• Issue: asyncio: potential leak of TLS connections #106684

[Yhg1s]

I think this should go into rc2, but without the warning. I think the warning is too potentially disruptive this late in the release cycle.

[miss-islington]

Thanks @miss-islington for the PR, and @Yhg1s for merging it 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[bedevere-bot]

GH-107836 is a backport of this pull request to the 3.11 branch.

[rigens]

It seems that closing the connection in the StreamWriter's __del__ method is not a good idea. Consider the following use case

importasyncioHOST='ifconfig.me'PORT=80asyncdefconnect() ->asyncio.Transport: reader, writer=awaitasyncio.open_connection( host=HOST, port=PORT, ) returnwriter.transportasyncdeffetch(): loop=asyncio.get_running_loop() transport=awaitconnect() # !!! transport is already closed here after this PR mergedreader=asyncio.StreamReader(limit=2**16, loop=loop) protocol=asyncio.StreamReaderProtocol(reader, loop=loop) transport.set_protocol(protocol) loop.call_soon(protocol.connection_made, transport) loop.call_soon(transport.resume_reading) writer=asyncio.StreamWriter( transport=transport, protocol=protocol, reader=reader, loop=loop, ) request=f'GET /ip HTTP/1.1\r\nHost: {HOST}\r\nConnection: close\r\n\r\n'.encode() writer.write(request) awaitwriter.drain() response=awaitreader.read(-1) print(response) if__name__=='__main__': asyncio.run(fetch())