gh-93453: No longer create an event loop in get_event_loop() (#98440)

asyncio.get_event_loop() now always return either running event loop or
the result of get_event_loop_policy().get_event_loop() call. The latter
should now raise an RuntimeError if no current event loop was set
instead of creating and setting a new event loop.

It affects also a number of asyncio functions and constructors which
call get_event_loop() implicitly: ensure_future(), shield(), gather(),
etc.

DeprecationWarning is no longer emitted if there is no running event loop but
the current event loop was set.

Co-authored-by: Łukasz Langa <lukasz@langa.pl>

1 files changed, 8 insertions, 16 deletions

diff --git a/Lib/test/test_asyncio/test_futures.py b/Lib/test/test_asyncio/test_futures.py
index 83ea01c245..56b0b864de 100644
--- a/Lib/test/test_asyncio/test_futures.py
+++ b/Lib/test/test_asyncio/test_futures.py
@@ -146,10 +146,8 @@ class BaseFutureTests:
         self.assertTrue(f.cancelled())
 
     def test_constructor_without_loop(self):
-        with self.assertWarns(DeprecationWarning) as cm:
-            with self.assertRaisesRegex(RuntimeError, 'There is no current event loop'):
-                self._new_future()
-        self.assertEqual(cm.filename, __file__)
+        with self.assertRaisesRegex(RuntimeError, 'no current event loop'):
+            self._new_future()
 
     def test_constructor_use_running_loop(self):
         async def test():
@@ -159,12 +157,10 @@ class BaseFutureTests:
         self.assertIs(f.get_loop(), self.loop)
 
     def test_constructor_use_global_loop(self):
-        # Deprecated in 3.10
+        # Deprecated in 3.10, undeprecated in 3.12
         asyncio.set_event_loop(self.loop)
         self.addCleanup(asyncio.set_event_loop, None)
-        with self.assertWarns(DeprecationWarning) as cm:
-            f = self._new_future()
-        self.assertEqual(cm.filename, __file__)
+        f = self._new_future()
         self.assertIs(f._loop, self.loop)
         self.assertIs(f.get_loop(), self.loop)
 
@@ -500,10 +496,8 @@ class BaseFutureTests:
             return (arg, threading.get_ident())
         ex = concurrent.futures.ThreadPoolExecutor(1)
         f1 = ex.submit(run, 'oi')
-        with self.assertWarns(DeprecationWarning) as cm:
-            with self.assertRaises(RuntimeError):
-                asyncio.wrap_future(f1)
-        self.assertEqual(cm.filename, __file__)
+        with self.assertRaisesRegex(RuntimeError, 'no current event loop'):
+            asyncio.wrap_future(f1)
         ex.shutdown(wait=True)
 
     def test_wrap_future_use_running_loop(self):
@@ -518,16 +512,14 @@ class BaseFutureTests:
         ex.shutdown(wait=True)
 
     def test_wrap_future_use_global_loop(self):
-        # Deprecated in 3.10
+        # Deprecated in 3.10, undeprecated in 3.12
         asyncio.set_event_loop(self.loop)
         self.addCleanup(asyncio.set_event_loop, None)
         def run(arg):
             return (arg, threading.get_ident())
         ex = concurrent.futures.ThreadPoolExecutor(1)
         f1 = ex.submit(run, 'oi')
-        with self.assertWarns(DeprecationWarning) as cm:
-            f2 = asyncio.wrap_future(f1)
-        self.assertEqual(cm.filename, __file__)
+        f2 = asyncio.wrap_future(f1)
         self.assertIs(self.loop, f2._loop)
         ex.shutdown(wait=True)