bpo-38599: Deprecate creation of asyncio object when the loop is not running

Lib/asyncio/locks.py

@@ -78,12 +78,14 @@ def __init__(self, *, loop=None):
         self._waiters = None
         self._locked = False
         if loop is None:
-            self._loop = events.get_event_loop()
+            self._loop = events._get_running_loop()
+            if self._loop is None:
+                warnings.warn("The creation of asyncio objects outside a running "
+                              "event loop is deprecated as of Python 3.9.",
+                              DeprecationWarning, stacklevel=2)
+                self._loop = events.get_event_loop()
         else:
             self._loop = loop
-            warnings.warn("The loop argument is deprecated since Python 3.8, "
-                          "and scheduled for removal in Python 3.10.",
-                          DeprecationWarning, stacklevel=2)
 
     def __repr__(self):
         res = super().__repr__()
@@ -174,12 +176,14 @@ def __init__(self, *, loop=None):
         self._waiters = collections.deque()
         self._value = False
         if loop is None:
-            self._loop = events.get_event_loop()
+            self._loop = events._get_running_loop()
+            if self._loop is None:
+                warnings.warn("The creation of asyncio objects outside a running "
+                              "event loop is deprecated as of Python 3.9.",
+                              DeprecationWarning, stacklevel=2)
+                self._loop = events.get_event_loop()
         else:
             self._loop = loop
-            warnings.warn("The loop argument is deprecated since Python 3.8, "
-                          "and scheduled for removal in Python 3.10.",
-                          DeprecationWarning, stacklevel=2)
 
     def __repr__(self):
         res = super().__repr__()
@@ -241,12 +245,14 @@ class Condition(_ContextManagerMixin):
 
     def __init__(self, lock=None, *, loop=None):
         if loop is None:
-            self._loop = events.get_event_loop()
+            self._loop = events._get_running_loop()
+            if self._loop is None:
+                warnings.warn("The creation of asyncio objects outside a running "
+                              "event loop is deprecated as of Python 3.9.",
+                              DeprecationWarning, stacklevel=2)
+                self._loop = events.get_event_loop()
         else:
             self._loop = loop
-            warnings.warn("The loop argument is deprecated since Python 3.8, "
-                          "and scheduled for removal in Python 3.10.",
-                          DeprecationWarning, stacklevel=2)
 
         if lock is None:
             lock = Lock(loop=loop)
@@ -372,12 +378,14 @@ def __init__(self, value=1, *, loop=None):
         self._value = value
         self._waiters = collections.deque()
         if loop is None:
-            self._loop = events.get_event_loop()
+            self._loop = events._get_running_loop()
+            if self._loop is None:
+                warnings.warn("The creation of asyncio objects outside a running "
+                              "event loop is deprecated as of Python 3.9.",
+                              DeprecationWarning, stacklevel=2)
+                self._loop = events.get_event_loop()
         else:
             self._loop = loop
-            warnings.warn("The loop argument is deprecated since Python 3.8, "
-                          "and scheduled for removal in Python 3.10.",
-                          DeprecationWarning, stacklevel=2)
 
     def __repr__(self):
         res = super().__repr__()

Lib/asyncio/queues.py

@@ -32,12 +32,15 @@ class Queue:
 
     def __init__(self, maxsize=0, *, loop=None):
         if loop is None:
-            self._loop = events.get_event_loop()
+            self._loop = events._get_running_loop()
+            if self._loop is None:
+                warnings.warn("The creation of asyncio objects outside a running "
+                              "event loop is deprecated as of Python 3.9.",
+                              DeprecationWarning, stacklevel=2)
+                self._loop = events.get_event_loop()
         else:
             self._loop = loop
-            warnings.warn("The loop argument is deprecated since Python 3.8, "
-                          "and scheduled for removal in Python 3.10.",
-                          DeprecationWarning, stacklevel=2)
+
         self._maxsize = maxsize
 
         # Futures.

Lib/test/test_asyncio/test_locks.py

@@ -1000,5 +1000,34 @@ def test_release_no_waiters(self):
         self.assertFalse(sem.locked())
 
 
+class LockLoopTests:
+    """Tests the deprecation of creating asyncio objects outside of a
+    running event loop."""
+
+    def setUp(self):
+        self.loop = asyncio.new_event_loop()
+        asyncio.set_event_loop(self.loop)
+
+    def tearDown(self):
+        asyncio.set_event_loop(None)
+        self.loop.close()
+
+    def test_lock_loop_not_running(self):
+        with self.assertWarns(DeprecationWarning):
+            asyncio.Lock()
+
+    def test_event_loop_not_running(self):
+        with self.assertWarns(DeprecationWarning):
+            asyncio.Event()
+
+    def test_condition_loop_not_running(self):
+        with self.assertWarns(DeprecationWarning):
+            asyncio.Condition()
+
+    def test_semaphore_loop_not_running(self):
+        with self.assertWarns(DeprecationWarning):
+            asyncio.Semaphore()
+
+
 if __name__ == '__main__':
     unittest.main()

Lib/test/test_asyncio/test_queues.py

@@ -714,5 +714,22 @@ class PriorityQueueJoinTests(_QueueJoinTestMixin, _QueueTestBase):
     q_class = asyncio.PriorityQueue
 
 
+class QueueLoopTests:
+    """Tests the deprecation of creating asyncio objects outside of a
+    running event loop."""
+
+    def setUp(self):
+        self.loop = asyncio.new_event_loop()
+        asyncio.set_event_loop(self.loop)
+
+    def tearDown(self):
+        asyncio.set_event_loop(None)
+        self.loop.close()
+
+    def test_queue_loop_not_running(self):
+        with self.assertWarns(DeprecationWarning):
+            asyncio.Queue()
+
+
 if __name__ == '__main__':
     unittest.main()

Misc/NEWS.d/next/Library/2020-01-26-20-54-04.bpo-38599.0PObOD.rst

@@ -0,0 +1,4 @@
+The creation of :class:`asyncio.Queue`, :class:`asyncio.Lock`,
+:class:`asyncio.Event`, :class:`asyncio.Condition`,
+:class:`asyncio.Semaphore`, and :class:`asyncio.BoundedSemaphore`
+objects outside of a running event loop has been deprecated.