gh-127949: deprecate `asyncio.get_event_loop_policy` (#128053)

This deprecates `asyncio.get_event_loop_policy` and will be removed in Python 3.16.

Doc/library/asyncio-policy.rst

@@ -40,6 +40,10 @@ for the current process:
 
    Return the current process-wide policy.
 
+   .. deprecated:: next
+      The :func:`get_event_loop_policy` function is deprecated and
+      will be removed in Python 3.16.
+
 .. function:: set_event_loop_policy(policy)
 
    Set the current process-wide policy to *policy*.

Lib/asyncio/events.py

@@ -8,6 +8,7 @@
     'AbstractEventLoopPolicy',
     'AbstractEventLoop', 'AbstractServer',
     'Handle', 'TimerHandle',
+    '_get_event_loop_policy',
     'get_event_loop_policy',
     '_set_event_loop_policy',
     'set_event_loop_policy',
@@ -761,12 +762,15 @@ def _init_event_loop_policy():
             _event_loop_policy = DefaultEventLoopPolicy()
 
 
-def get_event_loop_policy():
+def _get_event_loop_policy():
     """Get the current event loop policy."""
     if _event_loop_policy is None:
         _init_event_loop_policy()
     return _event_loop_policy
 
+def get_event_loop_policy():
+    warnings._deprecated('asyncio.get_event_loop_policy', remove=(3, 16))
+    return _get_event_loop_policy()
 
 def _set_event_loop_policy(policy):
     """Set the current event loop policy.
@@ -778,7 +782,7 @@ def _set_event_loop_policy(policy):
     _event_loop_policy = policy
 
 def set_event_loop_policy(policy):
-    warnings._deprecated('set_event_loop_policy', remove=(3,16))
+    warnings._deprecated('asyncio.set_event_loop_policy', remove=(3,16))
     _set_event_loop_policy(policy)
 
 def get_event_loop():
@@ -794,17 +798,17 @@ def get_event_loop():
     current_loop = _get_running_loop()
     if current_loop is not None:
         return current_loop
-    return get_event_loop_policy().get_event_loop()
+    return _get_event_loop_policy().get_event_loop()
 
 
 def set_event_loop(loop):
     """Equivalent to calling get_event_loop_policy().set_event_loop(loop)."""
-    get_event_loop_policy().set_event_loop(loop)
+    _get_event_loop_policy().set_event_loop(loop)
 
 
 def new_event_loop():
     """Equivalent to calling get_event_loop_policy().new_event_loop()."""
-    return get_event_loop_policy().new_event_loop()
+    return _get_event_loop_policy().new_event_loop()
 
 
 # Alias pure-Python implementations for testing purposes.

Lib/test/test_asyncio/test_events.py

@@ -2397,7 +2397,7 @@ def test_handle_repr_debug(self):
         self.assertRegex(repr(h), regex)
 
     def test_handle_source_traceback(self):
-        loop = asyncio.get_event_loop_policy().new_event_loop()
+        loop = asyncio.new_event_loop()
         loop.set_debug(True)
         self.set_event_loop(loop)
 
@@ -2759,24 +2759,31 @@ def test_set_event_loop(self):
         old_loop.close()
 
     def test_get_event_loop_policy(self):
-        policy = asyncio.get_event_loop_policy()
+        with self.assertWarnsRegex(
-        self.assertIsInstance(policy, asyncio.AbstractEventLoopPolicy)
+                DeprecationWarning, "'asyncio.get_event_loop_policy' is deprecated"):
-        self.assertIs(policy, asyncio.get_event_loop_policy())
+            policy = asyncio.get_event_loop_policy()
+            self.assertIsInstance(policy, asyncio.AbstractEventLoopPolicy)
+            self.assertIs(policy, asyncio.get_event_loop_policy())
 
     def test_set_event_loop_policy(self):
         with self.assertWarnsRegex(
-                DeprecationWarning, "'set_event_loop_policy' is deprecated"):
+                DeprecationWarning, "'asyncio.set_event_loop_policy' is deprecated"):
             self.assertRaises(
                 TypeError, asyncio.set_event_loop_policy, object())
 
-        old_policy = asyncio.get_event_loop_policy()
+        with self.assertWarnsRegex(
+                DeprecationWarning, "'asyncio.get_event_loop_policy' is deprecated"):
+            old_policy = asyncio.get_event_loop_policy()
 
         policy = asyncio.DefaultEventLoopPolicy()
         with self.assertWarnsRegex(
-                DeprecationWarning, "'set_event_loop_policy' is deprecated"):
+                DeprecationWarning, "'asyncio.set_event_loop_policy' is deprecated"):
             asyncio.set_event_loop_policy(policy)
-        self.assertIs(policy, asyncio.get_event_loop_policy())
+
-        self.assertIsNot(policy, old_policy)
+        with self.assertWarnsRegex(
+                DeprecationWarning, "'asyncio.get_event_loop_policy' is deprecated"):
+            self.assertIs(policy, asyncio.get_event_loop_policy())
+            self.assertIsNot(policy, old_policy)
 
 
 class GetEventLoopTestsMixin:
@@ -2859,7 +2866,7 @@ class Policy(asyncio.DefaultEventLoopPolicy):
             def get_event_loop(self):
                 raise TestError
 
-        old_policy = asyncio.get_event_loop_policy()
+        old_policy = asyncio._get_event_loop_policy()
         try:
             asyncio._set_event_loop_policy(Policy())
             loop = asyncio.new_event_loop()
@@ -2899,7 +2906,7 @@ async def func():
         self.assertIs(asyncio._get_running_loop(), None)
 
     def test_get_event_loop_returns_running_loop2(self):
-        old_policy = asyncio.get_event_loop_policy()
+        old_policy = asyncio._get_event_loop_policy()
         try:
             asyncio._set_event_loop_policy(asyncio.DefaultEventLoopPolicy())
             loop = asyncio.new_event_loop()

Lib/test/test_asyncio/test_runners.py

@@ -64,7 +64,7 @@ def setUp(self):
         asyncio._set_event_loop_policy(policy)
 
     def tearDown(self):
-        policy = asyncio.get_event_loop_policy()
+        policy = asyncio._get_event_loop_policy()
         if policy.loop is not None:
             self.assertTrue(policy.loop.is_closed())
             self.assertTrue(policy.loop.shutdown_ag_run)
@@ -208,7 +208,7 @@ async def main():
             await asyncio.sleep(0)
             return 42
 
-        policy = asyncio.get_event_loop_policy()
+        policy = asyncio._get_event_loop_policy()
         policy.set_event_loop = mock.Mock()
         asyncio.run(main())
         self.assertTrue(policy.set_event_loop.called)
@@ -495,7 +495,7 @@ def test_set_event_loop_called_once(self):
         async def coro():
             pass
 
-        policy = asyncio.get_event_loop_policy()
+        policy = asyncio._get_event_loop_policy()
         policy.set_event_loop = mock.Mock()
         runner = asyncio.Runner()
         runner.run(coro())

Lib/test/test_asyncio/test_subprocess.py

@@ -886,8 +886,7 @@ class SubprocessWatcherMixin(SubprocessMixin):
 
         def setUp(self):
             super().setUp()
-            policy = asyncio.get_event_loop_policy()
+            self.loop = asyncio.new_event_loop()
-            self.loop = policy.new_event_loop()
             self.set_event_loop(self.loop)
 
         def test_watcher_implementation(self):

Lib/test/test_asyncio/test_windows_events.py

@@ -332,7 +332,7 @@ async def main():
                 asyncio.get_running_loop(),
                 asyncio.SelectorEventLoop)
 
-        old_policy = asyncio.get_event_loop_policy()
+        old_policy = asyncio._get_event_loop_policy()
         try:
             asyncio._set_event_loop_policy(
                 asyncio.WindowsSelectorEventLoopPolicy())
@@ -346,7 +346,7 @@ async def main():
                 asyncio.get_running_loop(),
                 asyncio.ProactorEventLoop)
 
-        old_policy = asyncio.get_event_loop_policy()
+        old_policy = asyncio._get_event_loop_policy()
         try:
             asyncio._set_event_loop_policy(
                 asyncio.WindowsProactorEventLoopPolicy())

Lib/test/test_contextlib_async.py

@@ -496,7 +496,7 @@ class TestAsyncExitStack(TestBaseExitStack, unittest.IsolatedAsyncioTestCase):
     class SyncAsyncExitStack(AsyncExitStack):
         @staticmethod
         def run_coroutine(coro):
-            loop = asyncio.get_event_loop_policy().get_event_loop()
+            loop = asyncio.new_event_loop()
             t = loop.create_task(coro)
             t.add_done_callback(lambda f: loop.stop())
             loop.run_forever()

Lib/test/test_unittest/test_async_case.py

@@ -480,7 +480,7 @@ def test_setup_get_event_loop(self):
 
         class TestCase1(unittest.IsolatedAsyncioTestCase):
             def setUp(self):
-                asyncio.get_event_loop_policy().get_event_loop()
+                asyncio._get_event_loop_policy().get_event_loop()
 
             async def test_demo1(self):
                 pass

Modules/_asynciomodule.c

@@ -3773,7 +3773,7 @@ module_init(asyncio_state *state)
     }
 
     WITH_MOD("asyncio.events")
-    GET_MOD_ATTR(state->asyncio_get_event_loop_policy, "get_event_loop_policy")
+    GET_MOD_ATTR(state->asyncio_get_event_loop_policy, "_get_event_loop_policy")
 
     WITH_MOD("asyncio.base_futures")
     GET_MOD_ATTR(state->asyncio_future_repr_func, "_future_repr")