gh-145030: Address review: rename carve-out and assert st_nlink

Rename is_named_fifo_on_macos to is_named_fifo_on_apple to match the
Apple platform set, and assert st_nlink != 0 in the named FIFO test.

Author: bhuvi27

Lib/asyncio/unix_events.py

@@ -665,12 +665,12 @@ def __init__(self, loop, pipe, protocol, waiter=None, extra=None):
         # ever report a false disconnection (gh-145030). The same xnu
         # behaviour applies on iOS/tvOS/watchOS (sys.platform is not
         # "darwin" there).
-        is_named_fifo_on_macos = (
+        is_named_fifo_on_apple = (
             sys.platform in {"darwin", "ios", "tvos", "watchos"}
             and is_fifo and pipe_stat.st_nlink > 0)
         if is_socket or (is_fifo
                          and not sys.platform.startswith("aix")
-                         and not is_named_fifo_on_macos):
+                         and not is_named_fifo_on_apple):
             # only start reading when connection_made() has been called
             self._loop.call_soon(self._loop._add_reader,
                                  self._fileno, self._read_ready)

Lib/test/test_asyncio/test_events.py

@@ -1735,6 +1735,7 @@ def test_write_named_fifo_unread_data(self):
         # and close itself.
         path = os_helper.TESTFN
         os.mkfifo(path)
+        self.assertNotEqual(os.stat(path).st_nlink, 0)
         self.addCleanup(os_helper.unlink, path)
         rfd = os.open(path, os.O_RDONLY | os.O_NONBLOCK)
         self.addCleanup(os.close, rfd)