Error with Python 3.10: "ValueError: loop argument must agree with lock"

I ran into this in my own project, see https://github.com/simonw/datasette/pull/1481 - then I tried using a fork of this project to run the unit tests against Python 3.10 and got the same error: https://github.com/simonw/janus/runs/3842463703?check_suite_focus=true

 ============================= test session starts ==============================
 platform linux -- Python 3.10.0, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
 rootdir: /home/runner/work/janus/janus
 plugins: cov-2.12.1, asyncio-0.15.1
 collected 72 items
 
 tests/test_async.py FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF                      [ 43%]
 tests/test_mixed.py .FFFFFFFFFFFFFFFFF                                   [ 68%]
 tests/test_sync.py FFFFFFFFFFFFFFFFFFFFFFF                               [100%]
 
 =================================== FAILURES ===================================
 __________________________ TestQueueBasic.test_empty ___________________________
 
 self = <test_async.TestQueueBasic object at 0x7fb0f561e4d0>
 
     @pytest.mark.asyncio
     async def test_empty(self):
 >       _q = janus.Queue()
 
 tests/test_async.py:65: 
 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
 janus/__init__.py:39: in __init__
     self._async_not_empty = asyncio.Condition(self._async_mutex)
 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
 
 self = <[AttributeError("'Condition' object has no attribute 'locked'") raised in repr()] Condition object at 0x7fb0f569a620>
 lock = <asyncio.locks.Lock object at 0x7fb0f569ada0 [unlocked]>
 
     def __init__(self, lock=None, *, loop=mixins._marker):
         super().__init__(loop=loop)
         if lock is None:
             lock = Lock()
         elif lock._loop is not self._get_loop():
 >           raise ValueError("loop argument must agree with lock")
 E           ValueError: loop argument must agree with lock

[asvetlov]

janus 0.6.2 released with the fix

[simonw]

That addressed the bug!

diff --git a/janus/__init__.py b/janus/__init__.py
index 789f12f..a2375b6 100644
--- a/janus/__init__.py
+++ b/janus/__init__.py
@@ -36,6 +36,8 @@ class Queue(Generic[T]):
         self._all_tasks_done = threading.Condition(self._sync_mutex)
 
         self._async_mutex = asyncio.Lock()
+        # Workaround for issue #358:
+        getattr(self._async_mutex, '_get_loop', lambda: None)()
         self._async_not_empty = asyncio.Condition(self._async_mutex)
         self._async_not_full = asyncio.Condition(self._async_mutex)
         self._finished = asyncio.Event()

(janus) janus % pytest -x      
============================================================= test session starts ==============================================================
platform darwin -- Python 3.10.0, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
rootdir: /Users/simon/Dropbox/Development/janus
plugins: cov-2.12.1, asyncio-0.15.1
collected 72 items                                                                                                                             

tests/test_async.py ...............................                                                                                      [ 43%]
tests/test_mixed.py ..................                                                                                                   [ 68%]
tests/test_sync.py .......................                                                                                               [100%]

============================================================== 72 passed in 5.34s ==============================================================