make `asyncio.iscoroutinefunction` a deprecated alias of `inspect.iscoroutinefunction` and remove `asyncio.coroutines._is_coroutine`

[graingert]

currently asyncio.iscoroutinefunction and inspect.iscoroutinefunction behave differently in confusing and hard to document ways. It's possible to bring them into alignment but I think it would be better to make asyncio.iscoroutinefunction a deprecated alias of inspect.iscoroutinefunction and remove asyncio.coroutines._is_coroutine.

This is now possible with the recent removal of @asyncio.coroutine and support for AsyncMock and other duck-type functions in inspect.iscoroutinefunction

the only caveats are - what should happen to users of the asyncio.coroutines._is_coroutine mark? eg:

cpython/Lib/asyncio/tasks.py

Lines 686 to 696 in 1c0cf0a

	@types.coroutine
	def _wrap_awaitable(awaitable):
	"""Helper for asyncio.ensure_future().
	Wraps awaitable (an object with __await__) into a coroutine
	that will later be wrapped in a Task by ensure_future().
	"""
	return (yield from awaitable.__await__())
	_wrap_awaitable._is_coroutine = _is_coroutine

and all of these:

Lib/test/test_asyncio/test_base_events.py:    m_socket.getaddrinfo._is_coroutine = False
Lib/test/test_asyncio/test_base_events.py:        self.loop._add_reader._is_coroutine = False
Lib/test/test_asyncio/test_base_events.py:        self.loop._add_writer._is_coroutine = False
Lib/test/test_asyncio/test_base_events.py:        self.loop._add_reader._is_coroutine = False
Lib/test/test_asyncio/test_base_events.py:        self.loop._add_writer._is_coroutine = False
Lib/test/test_asyncio/test_base_events.py:        self.loop._add_reader._is_coroutine = False
Lib/test/test_asyncio/test_base_events.py:        self.loop._add_writer._is_coroutine = False
Lib/test/test_asyncio/test_base_events.py:        m_socket.getaddrinfo._is_coroutine = False
Lib/test/test_asyncio/test_base_events.py:        m_socket.getaddrinfo._is_coroutine = False
Lib/test/test_asyncio/test_base_events.py:        self.loop._add_reader._is_coroutine = False
Lib/test/test_asyncio/test_selector_events.py:        self.loop.add_reader._is_coroutine = False
Lib/test/test_asyncio/test_subprocess.py:        protocol.connection_made._is_coroutine = False
Lib/test/test_asyncio/test_subprocess.py:        protocol.process_exited._is_coroutine = False
Lib/unittest/mock.py:    mock._is_coroutine = asyncio.coroutines._is_coroutine
Lib/unittest/mock.py:        # iscoroutinefunction() checks _is_coroutine property to say if an
Lib/unittest/mock.py:        self.__dict__['_is_coroutine'] = asyncio.coroutines._is_coroutine

• PR: gh-94912: Added marker for non-standard coroutine function detection #99247

• PR: gh-94912: Adjusted check for non-standard coroutine function marker. #100935

[graingert]

changing _wrap_awaitable to be:

async def _wrap_awaitable(awaitable): 
   """Helper for asyncio.ensure_future(). 
  
   Wraps awaitable (an object with __await__) into a coroutine 
   that will later be wrapped in a Task by ensure_future(). 
   """ 
   return await awaitable

would have a few subtle changes - eg the if not called_wrap_awaitable check in asyncio.ensure_future(...) isn't needed anymore, and this would prevent wrapping objects that have .__dict__["__await__"] callables

[graingert]

I'm pretty sure all of the assignments in the test suite of protocol.process_exited._is_coroutine = False etc, are redundant or worse, invalidated by #94050 Edit: yes they are redundant see https://github.com/python/cpython/pull/94926/files#r922839081

the mock._is_coroutine = asyncio.coroutines._is_coroutine use in unittest.mock is also probably safe to remove?

[graingert]

aha I've just checked and the protocol.process_exited._is_coroutine = False lines were made redundant in python/asyncio#459

[gvanrossum]

So that's the ancient external asyncio project, which nobody should use any more. Does the corresponding code (or corresponding commits) exist in the stdlib version?

[graingert]

So that's the ancient external asyncio project, which nobody should use any more. Does the corresponding code (or corresponding commits) exist in the stdlib version?

Yep, the fix was ported everywhere but the now redundant workarounds were left in, there's more info here https://github.com/python/cpython/pull/94926/files#r922839081

[kumaraditya303]

Before making it a deprecated alias, it would be better to investigate:

• How much code will be affected by this change?
• How this interacts with cython coroutines?

[graingert]

Before making it a deprecated alias, it would be better to investigate:

* How much code will be affected by this change?

how about if I just add a deprecation notice and leave the implementation alone?

* How this interacts with cython coroutines?

inspect.iscoroutinefunction now uses inspect._signature_is_functionlike and so it should 'just work', I've let them know and will work on a cython test case to make sure

[gvanrossum]

how about if I just add a deprecation notice and leave the implementation alone?

That's rarely a good strategy. Many people don't read the docs and keep using the function (if they are using it) and so once the deprecated function is deleted their code breaks without warning.

[graingert]

how about if I just add a deprecation notice and leave the implementation alone?

That's rarely a good strategy. Many people don't read the docs and keep using the function (if they are using it) and so once the deprecated function is deleted their code breaks without warning.

The alternative is asyncio.iscoroutinefunction starts returning False when it used to return True, which will break user code in a silent way

[gvanrossum]

I thought we were talking about putting a warning in it? It should only warn when it's going to return True but the inspect function would return False.

[graingert]

It should only warn when it's going to return True but the inspect function would return False.

ok I've pushed that change