`test_contextlib_async` produces several `RuntimeWarning`s

[sobolevn]

Bug report

» ./python.exe -m test test_contextlib_async
Using random seed 908291980
0:00:00 load avg: 4.08 Run 1 test sequentially
0:00:00 load avg: 4.08 [1/1] test_contextlib_async
/Users/sobolev/Desktop/cpython/Lib/contextlib.py:701: RuntimeWarning: coroutine method 'aclose' of 'AsyncContextManagerTestCase.test_contextmanager_trap_second_yield.<locals>.whoo' was never awaited
  async def __aenter__(self):
RuntimeWarning: Enable tracemalloc to get the object allocation traceback
/Users/sobolev/Desktop/cpython/Lib/contextlib.py:701: RuntimeWarning: coroutine method 'aclose' of 'AsyncContextManagerTestCase.test_contextmanager_trap_yield_after_throw.<locals>.whoo' was never awaited
  async def __aenter__(self):
RuntimeWarning: Enable tracemalloc to get the object allocation traceback
/Users/sobolev/Desktop/cpython/Lib/contextlib.py:701: RuntimeWarning: coroutine method 'aclose' of 'TestAbstractAsyncContextManager.test_async_gen_propagates_generator_exit.<locals>.gen' was never awaited
  async def __aenter__(self):
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

== Tests result: SUCCESS ==

1 test OK.

Total duration: 121 ms
Total tests: run=58
Total test files: run=1/1
Result: SUCCESS

This can be fixed by moving away from legacy @_async_test and by using stabel IsolatedAsyncioTestCase.

cpython/Lib/test/test_contextlib_async.py

Lines 14 to 20 in 6592976

	def _async_test(func):
	"""Decorator to turn an async function into a test case."""
	@functools.wraps(func)
	def wrapper(*args, **kwargs):
	coro = func(*args, **kwargs)
	asyncio.run(coro)
	return wrapper

Linked PRs

• gh-110378: Move to IsolatedAsyncTestCase in test_contextlib_async.py #110379
• gh-110378: Close invalid generators in contextmanager and asynccontextmanager #110499
• gh-110378: Fix test_async_gen_propagates_generator_exit in test_contextlib_async #110500
• [3.12] gh-110378: Close invalid generators in contextmanager and asynccontextmanager (GH-110499) #110588
• [3.11] gh-110378: Close invalid generators in contextmanager and asynccontextmanager (GH-110499) #110589
• [3.12] gh-110378: Fix test_async_gen_propagates_generator_exit in test_contextlib_async (GH-110500) #110610
• [3.11] gh-110378: Fix test_async_gen_propagates_generator_exit in test_contextlib_async (GH-110500) #110611

[serhiy-storchaka]

There are two issues here.

1. test_async_gen_propagates_generator_exit (added in bpo-33786/@asynccontextmanager doesn't work well with async generators #77967, PR bpo-33786: Fix asynchronous generators to handle GeneratorExit in athrow() #7467) creates an asynchronous generator, but do not iterate it to the end (it would close it implicitly) and do not close it explicitly. Actually, this test does not work at all. It is passed with unpatched code, it only prints a traceback from implicitly called destructor. It also contains code not related to the issue. This test should be rewritten.
2. test_contextmanager_trap_yield_after_throw and test_contextmanager_trap_second_yield test asynccontextmanager with an asynchronous generator with second yield. asynccontextmanager raises RuntimeError, but leaves the underlying asynchronous generator object not closed. Such generator is a programming error, and we don't have to clean up after this, but the "gen" attribute of asynccontextmanager object is an implementation detail, so it is better to not leave it to user and do clean up. The __exit__ method should close the underlying asynchronous generator object.

Moving to IsolatedAsyncioTestCase looks like a good thing, but only after fixing the deeper issues.