gh-90980: skip getaddrinfo thread if host is already resolved, using socket.AI_NUMERIC...

[graingert]

#90980

https://bugs.python.org/issue46824

• Issue: use AI_NUMERICHOST | AI_NUMERICSERV to skip getaddrinfo thread in asyncio #90980

[graingert]

this is inspired by the implementation from trio https://github.com/python-trio/trio/blob/4edfd41bd5519a2e626e87f6c6ca9fb32b90a6f4/trio/_socket.py#L125-L192

[graingert]

test_create_connection_ipv6_scope is failing because asyncio.get_running_loop().sock_connect ignores the flowinfo and scope of hosts resolved via getaddrinfo:

FAIL: test_create_connection_ipv6_scope (test.test_asyncio.test_base_events.BaseEventLoopWithSelectorTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/runner/work/cpython/cpython-ro-srcdir/Lib/contextlib.py", line 155, in __exit__
    self.gen.throw(typ, value, traceback)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython-ro-srcdir/Lib/unittest/mock.py", line 1345, in decoration_helper
    yield (args, keywargs)
    ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython-ro-srcdir/Lib/unittest/mock.py", line 1359, in patched
    return func(*newargs, **newkeywargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython-ro-srcdir/Lib/test/test_asyncio/test_base_events.py", line 1244, in test_create_connection_ipv6_scope
    sock.connect.assert_called_with(('fe80::1', 80, 0, 1))
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython-ro-srcdir/Lib/unittest/mock.py", line 923, in assert_called_with
    raise AssertionError(_error_message()) from cause
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: expected call not found.
Expected: connect(('fe80::1', 80, 0, 1))
Actual: connect(('fe80::1', 80, 0, 0))

eg what should asyncio.get_running_loop().sock_connect(sock, ("google.com", 80, 0, 1)) do? currently it discards the scope=1 and uses whatever scope DNS getaddrinfo returns.

[MaxwellDupre]

Lets hope comments on slow Mac back in 2015 are resolved. Otherwise a nice optimisation.

[github-actions]

This PR is stale because it has been open for 30 days with no activity.