Issue #28368: Refuse monitoring processes if the child watcher has no loop attached.

Patch by Vincent Michel.

1 files changed, 7 insertions, 0 deletions

diff --git a/Lib/test/test_asyncio/test_subprocess.py b/Lib/test/test_asyncio/test_subprocess.py
index 58f7253..1531023 100644
--- a/Lib/test/test_asyncio/test_subprocess.py
+++ b/Lib/test/test_asyncio/test_subprocess.py
@@ -433,6 +433,13 @@ class SubprocessMixin:
         # the transport was not notified yet
         self.assertFalse(killed)
 
+        # Unlike SafeChildWatcher, FastChildWatcher does not pop the
+        # callbacks if waitpid() is called elsewhere. Let's clear them
+        # manually to avoid a warning when the watcher is detached.
+        if sys.platform != 'win32' and \
+           isinstance(self, SubprocessFastWatcherTests):
+            asyncio.get_child_watcher()._callbacks.clear()
+
     def test_popen_error(self):
         # Issue #24763: check that the subprocess transport is closed
         # when BaseSubprocessTransport fails