``test_asyncio.test_streams`` raises a ``ResourceWarning``

[Eclips4]

Bug report

Bug description:

./python.exe -m test test_asyncio.test_streams

Using random seed: 4151462817
0:00:00 load avg: 28.75 Run 1 test sequentially
0:00:00 load avg: 28.75 [1/1] test_asyncio.test_streams
/Users/admin/Projects/cpython/Lib/asyncio/streams.py:410: ResourceWarning: unclosed <StreamWriter transport=<_SelectorSocketTransport closing fd=12 read=idle write=<idle, bufsize=0>> reader=<StreamReader transport=<_SelectorSocketTransport closing fd=12 read=idle write=<idle, bufsize=0>>>>
  warnings.warn(f"unclosed {self!r}", ResourceWarning)

== Tests result: SUCCESS ==

1 test OK.

Total duration: 1.5 sec
Total tests: run=69
Total test files: run=1/1
Result: SUCCESS

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-116112: Fix ResourceWarning in test_asyncio.test_stream #116371

[sobolevn]

Bisects to a355f60 CC @CendioOssman

[gvanrossum]

To be precise the error occurs in test_unhandled_cancel:

(.venv) ~/cpython$ ./python.exe -m test test_asyncio.test_streams -v -m test_unhandled_cancel
[...]
Using random seed: 781240745
0:00:00 load avg: 1.56 Run 1 test sequentially
0:00:00 load avg: 1.56 [1/1] test_asyncio.test_streams
test_unhandled_cancel (test.test_asyncio.test_streams.StreamTests.test_unhandled_cancel) ... /Users/guido/cpython/Lib/asyncio/streams.py:410: ResourceWarning: unclosed <StreamWriter transport=<_SelectorSocketTransport closing fd=11 read=idle write=<idle, bufsize=0>> reader=<StreamReader transport=<_SelectorSocketTransport closing fd=11 read=idle write=<idle, bufsize=0>>>>
  warnings.warn(f"unclosed {self!r}", ResourceWarning)
ok

[CendioOssman]

Thanks for letting me know. I'll try to have a look as soon as I'm able.

[CendioOssman]

In this case, the ResourceWarning is absolutely correct. The test does not correctly clean up the streams.

I am not sure why the same thing doesn't happen for test_unhandled_exception(). Maybe the StreamWriter gets tangled up in the exception stack and is kept alive?

The fix is this:

diff --git a/Lib/test/test_asyncio/test_streams.py b/Lib/test/test_asyncio/test_streams.py
index bf123ebf9b..2cf48538d5 100644
--- a/Lib/test/test_asyncio/test_streams.py
+++ b/Lib/test/test_asyncio/test_streams.py
@@ -1188,6 +1188,7 @@ async def handle_echo(reader, writer):
 
     def test_unhandled_cancel(self):
         async def handle_echo(reader, writer):
+            writer.close()
             asyncio.current_task().cancel()
         messages = self._basetest_unhandled_exceptions(handle_echo)
         self.assertEqual(messages, [])

Can someone easily commit this without a PR song and dance?

[sobolevn]

Can someone easily commit this without a PR song and dance?

No, this is not possible. All changes require a PR, CI run and proper review.
If you don't have time, I can help you (with crediting your work properly) :)

[CendioOssman]

That would be appreciated.