avoid recursion errors if weakrefs unresolve before close is called

Can occur when close is called via `__del__`, for instance when asyncio.run raises

Author: minrk

asyncio_atexit.py

@@ -21,12 +21,16 @@
 
 class _RegistryEntry:
     def __init__(self, loop):
+        if not hasattr(loop, "_atexit_orig_close"):
+            # avoid double-patching
+            # weakrefs can get unresolved and then close called in __del__,
+            # so this seems unavoidable
+            loop._atexit_orig_close = loop.close
         try:
-            self._close_ref = weakref.WeakMethod(loop.close)
+            self._close_ref = weakref.WeakMethod(loop._atexit_orig_close)
         except TypeError:
             # not everything can be weakref'd (Extensions such as uvloop).
             # Hold a regular reference _on the object_, in those cases
-            loop._atexit_orig_close = loop.close
             self._close_ref = lambda: loop._atexit_orig_close
         self.callbacks = []
 

test_asyncio_atexit.py

@@ -75,3 +75,20 @@ async def test():
 
     asyncio_run(test())
     assert not sync_called
+
+
+def test_run_raises(policy):
+    sync_called = False
+
+    def sync_cb():
+        nonlocal sync_called
+        sync_called = True
+
+    async def test():
+        asyncio_atexit.register(sync_cb)
+        1 / 0
+
+    with pytest.raises(ZeroDivisionError):
+        asyncio_run(test())
+
+    assert sync_called