gh-94597: deprecate asyncio.set_event_loop_policy

Doc/library/asyncio-policy.rst

@@ -7,6 +7,8 @@
 Policies
 ========
 
+The policy system is deprecated as of Python 3.13 and will
+be removed in Python 3.15 or later.
 An event loop policy is a global object
 used to get and set the current :ref:`event loop <asyncio-event-loop>`,
 as well as create new event loops.
@@ -46,6 +48,8 @@ for the current process:
 
    If *policy* is set to ``None``, the default policy is restored.
 
+   .. deprecated-removed:: 3.13 3.15
+
 
 .. _asyncio-policy-objects:
 

Doc/whatsnew/3.13.rst

@@ -358,6 +358,11 @@ Deprecated
   They will be removed in Python 3.15.
   (Contributed by Victor Stinner in :gh:`105096`.)
 
+* :mod:`asyncio`:
+
+  * :func:`asyncio.set_event_loop_policy` will be removed along with the
+    rest of the asyncio policy system in Python 3.15 or later.
+
 * Passing more than one positional argument to :func:`sqlite3.connect` and the
   :class:`sqlite3.Connection` constructor is deprecated. The remaining
   parameters will become keyword-only in Python 3.15.

Lib/asyncio/events.py

@@ -18,6 +18,7 @@
 import subprocess
 import sys
 import threading
+import warnings
 
 from . import format_helpers
 
@@ -787,6 +788,9 @@ def set_event_loop_policy(policy):
     """Set the current event loop policy.
 
     If policy is None, the default policy is restored."""
+    warnings._deprecated("set_event_loop_policy",
+                         "{name!r} is deprecated as of Python 3.13 and will be "
+                         "removed in Python {remove} or later.", remove=(3, 15))
     global _event_loop_policy
     if policy is not None and not isinstance(policy, AbstractEventLoopPolicy):
         raise TypeError(f"policy must be an instance of AbstractEventLoopPolicy or None, not '{type(policy).__name__}'")

Lib/test/libregrtest/save_env.py

@@ -96,8 +96,7 @@ def get_asyncio_events__event_loop_policy(self):
         self.try_get_module('asyncio')
         return support.maybe_get_event_loop_policy()
     def restore_asyncio_events__event_loop_policy(self, policy):
-        asyncio = self.get_module('asyncio')
-        asyncio.set_event_loop_policy(policy)
+        support.set_event_loop_policy(policy)
 
     def get_sys_argv(self):
         return id(sys.argv), sys.argv, sys.argv[:]

Lib/test/support/__init__.py

@@ -1892,6 +1892,13 @@ def maybe_get_event_loop_policy():
     import asyncio.events
     return asyncio.events._event_loop_policy
 
+def set_event_loop_policy(policy):
+    """Set the global event loop policy ignoring deprecation warnings"""
+    import asyncio
+    with warnings.catch_warnings():
+        warnings.simplefilter("ignore", DeprecationWarning)
+        asyncio.set_event_loop_policy(policy)
+
 # Helpers for testing hashing.
 NHASHBITS = sys.hash_info.width # number of bits in hash() result
 assert NHASHBITS in (32, 64)

Lib/test/test_asyncgen.py

@@ -5,6 +5,7 @@
 
 from test.support.import_helper import import_module
 from test.support import gc_collect, requires_working_socket
+from test import support
 asyncio = import_module("asyncio")
 
 
@@ -429,7 +430,7 @@ def setUp(self):
     def tearDown(self):
         self.loop.close()
         self.loop = None
-        asyncio.set_event_loop_policy(None)
+        support.set_event_loop_policy(None)
 
     def check_async_iterator_anext(self, ait_class):
         with self.subTest(anext="pure-Python"):

Lib/test/test_asyncio/test_base_events.py

@@ -24,7 +24,7 @@
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 def mock_socket_module():

Lib/test/test_asyncio/test_buffered_proto.py

@@ -2,10 +2,11 @@
 import unittest
 
 from test.test_asyncio import functional as func_tests
+from test import support
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 class ReceiveStuffProto(asyncio.BufferedProtocol):

Lib/test/test_asyncio/test_context.py

@@ -1,10 +1,11 @@
 import asyncio
 import decimal
 import unittest
+from test import support
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 @unittest.skipUnless(decimal.HAVE_CONTEXTVAR, "decimal is built with a thread-local context")

Lib/test/test_asyncio/test_eager_task_factory.py

@@ -8,12 +8,13 @@
 from asyncio import tasks
 from test.test_asyncio import utils as test_utils
 from test.support.script_helper import assert_python_ok
+from test import support
 
 MOCK_ANY = mock.ANY
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 class EagerTaskFactoryLoopTests:

Lib/test/test_asyncio/test_events.py

@@ -39,7 +39,7 @@
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 def broken_unix_getsockname():
@@ -2684,13 +2684,15 @@ def test_get_event_loop_policy(self):
         self.assertIs(policy, asyncio.get_event_loop_policy())
 
     def test_set_event_loop_policy(self):
-        self.assertRaises(
-            TypeError, asyncio.set_event_loop_policy, object())
+        with self.assertWarns(DeprecationWarning):
+            self.assertRaises(
+                TypeError, asyncio.set_event_loop_policy, object())
 
         old_policy = asyncio.get_event_loop_policy()
 
         policy = asyncio.DefaultEventLoopPolicy()
-        asyncio.set_event_loop_policy(policy)
+        with self.assertWarns(DeprecationWarning):
+            asyncio.set_event_loop_policy(policy)
         self.assertIs(policy, asyncio.get_event_loop_policy())
         self.assertIsNot(policy, old_policy)
 
@@ -2789,7 +2791,8 @@ def get_event_loop(self):
 
         old_policy = asyncio.get_event_loop_policy()
         try:
-            asyncio.set_event_loop_policy(Policy())
+            with self.assertWarns(DeprecationWarning):
+                asyncio.set_event_loop_policy(Policy())
             loop = asyncio.new_event_loop()
 
             with self.assertRaises(TestError):
@@ -2817,7 +2820,7 @@ async def func():
                 asyncio.get_event_loop()
 
         finally:
-            asyncio.set_event_loop_policy(old_policy)
+            support.set_event_loop_policy(old_policy)
             if loop is not None:
                 loop.close()
 
@@ -2829,7 +2832,8 @@ async def func():
     def test_get_event_loop_returns_running_loop2(self):
         old_policy = asyncio.get_event_loop_policy()
         try:
-            asyncio.set_event_loop_policy(asyncio.DefaultEventLoopPolicy())
+            with self.assertWarns(DeprecationWarning):
+                asyncio.set_event_loop_policy(asyncio.DefaultEventLoopPolicy())
             loop = asyncio.new_event_loop()
             self.addCleanup(loop.close)
 
@@ -2860,7 +2864,7 @@ async def func():
                 asyncio.get_event_loop()
 
         finally:
-            asyncio.set_event_loop_policy(old_policy)
+            support.set_event_loop_policy(old_policy)
             if loop is not None:
                 loop.close()
 

Lib/test/test_asyncio/test_futures.py

@@ -16,7 +16,7 @@
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 def _fakefunc(f):

Lib/test/test_asyncio/test_futures2.py

@@ -4,10 +4,11 @@
 import traceback
 import unittest
 from asyncio import tasks
+from test import support
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 class FutureTests:

Lib/test/test_asyncio/test_locks.py

@@ -6,6 +6,7 @@
 
 import asyncio
 import collections
+from test import support
 
 STR_RGX_REPR = (
     r'^<(?P<class>.*?) object at (?P<address>.*?)'
@@ -20,7 +21,7 @@
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 class LockTests(unittest.IsolatedAsyncioTestCase):

Lib/test/test_asyncio/test_pep492.py

@@ -8,10 +8,11 @@
 
 import asyncio
 from test.test_asyncio import utils as test_utils
+from test import support
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 # Test that asyncio.iscoroutine() uses collections.abc.Coroutine

Lib/test/test_asyncio/test_proactor_events.py

@@ -15,10 +15,11 @@
 from test.support import os_helper
 from test.support import socket_helper
 from test.test_asyncio import utils as test_utils
+from test import support
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 def close_transport(transport):

Lib/test/test_asyncio/test_protocols.py

@@ -2,12 +2,13 @@
 from unittest import mock
 
 import asyncio
+from test import support
 
 
 def tearDownModule():
     # not needed for the test file but added for uniformness with all other
     # asyncio test files for the sake of unified cleanup
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 class ProtocolsAbsTests(unittest.TestCase):

Lib/test/test_asyncio/test_queues.py

@@ -3,10 +3,11 @@
 import asyncio
 import unittest
 from types import GenericAlias
+from test import support
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 class QueueBasicTests(unittest.IsolatedAsyncioTestCase):

Lib/test/test_asyncio/test_runners.py

@@ -7,12 +7,13 @@
 import threading
 import unittest
 from test.test_asyncio import utils as test_utils
+from test import support
 from unittest import mock
 from unittest.mock import patch
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 def interrupt_self():
@@ -61,15 +62,15 @@ def setUp(self):
         super().setUp()
 
         policy = TestPolicy(self.new_loop)
-        asyncio.set_event_loop_policy(policy)
+        support.set_event_loop_policy(policy)
 
     def tearDown(self):
         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)
 
-        asyncio.set_event_loop_policy(None)
+        support.set_event_loop_policy(None)
         super().tearDown()
 
 
@@ -259,7 +260,7 @@ def new_event_loop():
             loop.set_task_factory(Task)
             return loop
 
-        asyncio.set_event_loop_policy(TestPolicy(new_event_loop))
+        support.set_event_loop_policy(TestPolicy(new_event_loop))
         with self.assertRaises(asyncio.CancelledError):
             asyncio.run(main())
 

Lib/test/test_asyncio/test_selector_events.py

@@ -19,12 +19,13 @@
                                      _SelectorSocketTransport,
                                      _SelectorTransport)
 from test.test_asyncio import utils as test_utils
+from test import support
 
 MOCK_ANY = mock.ANY
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 class TestBaseSelectorEventLoop(BaseSelectorEventLoop):

Lib/test/test_asyncio/test_sendfile.py

@@ -22,7 +22,7 @@
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 class MySendfileProto(asyncio.Protocol):

Lib/test/test_asyncio/test_server.py

@@ -6,10 +6,11 @@
 from test.support import socket_helper
 from test.test_asyncio import utils as test_utils
 from test.test_asyncio import functional as func_tests
+from test import support
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 class BaseStartServer(func_tests.FunctionalTestCaseMixin):

Lib/test/test_asyncio/test_sock_lowlevel.py

@@ -15,7 +15,7 @@
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 class MyProto(asyncio.Protocol):

Lib/test/test_asyncio/test_ssl.py

@@ -25,7 +25,7 @@
 
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    support.set_event_loop_policy(None)
 
 
 class MyBaseProto(asyncio.Protocol):