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_streams.py b/Lib/test/test_asyncio/test_streams.py
index 01d5407a497..7f9dc621808 100644
--- a/Lib/test/test_asyncio/test_streams.py
+++ b/Lib/test/test_asyncio/test_streams.py
@@ -816,10 +816,8 @@ os.close(fd)
         self.assertEqual(data, b'data')
 
     def test_streamreader_constructor_without_loop(self):
-        with self.assertWarns(DeprecationWarning) as cm:
-            with self.assertRaisesRegex(RuntimeError, 'There is no current event loop'):
-                asyncio.StreamReader()
-        self.assertEqual(cm.filename, __file__)
+        with self.assertRaisesRegex(RuntimeError, 'no current event loop'):
+            asyncio.StreamReader()
 
     def test_streamreader_constructor_use_running_loop(self):
         # asyncio issue #184: Ensure that StreamReaderProtocol constructor
@@ -833,21 +831,17 @@ os.close(fd)
     def test_streamreader_constructor_use_global_loop(self):
         # asyncio issue #184: Ensure that StreamReaderProtocol constructor
         # retrieves the current loop if the loop parameter is not set
-        # Deprecated in 3.10
+        # Deprecated in 3.10, undeprecated in 3.12
         self.addCleanup(asyncio.set_event_loop, None)
         asyncio.set_event_loop(self.loop)
-        with self.assertWarns(DeprecationWarning) as cm:
-            reader = asyncio.StreamReader()
-        self.assertEqual(cm.filename, __file__)
+        reader = asyncio.StreamReader()
         self.assertIs(reader._loop, self.loop)
 
 
     def test_streamreaderprotocol_constructor_without_loop(self):
         reader = mock.Mock()
-        with self.assertWarns(DeprecationWarning) as cm:
-            with self.assertRaisesRegex(RuntimeError, 'There is no current event loop'):
-                asyncio.StreamReaderProtocol(reader)
-        self.assertEqual(cm.filename, __file__)
+        with self.assertRaisesRegex(RuntimeError, 'no current event loop'):
+            asyncio.StreamReaderProtocol(reader)
 
     def test_streamreaderprotocol_constructor_use_running_loop(self):
         # asyncio issue #184: Ensure that StreamReaderProtocol constructor
@@ -861,13 +855,11 @@ os.close(fd)
     def test_streamreaderprotocol_constructor_use_global_loop(self):
         # asyncio issue #184: Ensure that StreamReaderProtocol constructor
         # retrieves the current loop if the loop parameter is not set
-        # Deprecated in 3.10
+        # Deprecated in 3.10, undeprecated in 3.12
         self.addCleanup(asyncio.set_event_loop, None)
         asyncio.set_event_loop(self.loop)
         reader = mock.Mock()
-        with self.assertWarns(DeprecationWarning) as cm:
-            protocol = asyncio.StreamReaderProtocol(reader)
-        self.assertEqual(cm.filename, __file__)
+        protocol = asyncio.StreamReaderProtocol(reader)
         self.assertIs(protocol._loop, self.loop)
 
     def test_multiple_drain(self):