GH-102748: remove legacy support for generator based coroutines from asyncio.iscoroutine (#102749)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

Doc/whatsnew/3.12.rst

@@ -237,6 +237,10 @@ asyncio
 * Add C implementation of :func:`asyncio.current_task` for 4x-6x speedup.
   (Contributed by Itamar Ostricher and Pranav Thulasiram Bhat in :gh:`100344`.)
 
+* :func:`asyncio.iscoroutine` now returns ``False`` for generators as
+  :mod:`asyncio` does not support legacy generator-based coroutines.
+  (Contributed by Kumar Aditya in :gh:`102748`.)
+
 inspect
 -------
 

Lib/asyncio/coroutines.py

@@ -25,8 +25,7 @@ def iscoroutinefunction(func):
 
 # Prioritize native coroutine check to speed-up
 # asyncio.iscoroutine.
-_COROUTINE_TYPES = (types.CoroutineType, types.GeneratorType,
-                    collections.abc.Coroutine)
+_COROUTINE_TYPES = (types.CoroutineType, collections.abc.Coroutine)
 _iscoroutine_typecache = set()
 
 

Lib/test/test_asyncio/test_pep492.py

@@ -119,6 +119,12 @@ async def foo(): pass
 
         self.assertTrue(asyncio.iscoroutine(FakeCoro()))
 
+    def test_iscoroutine_generator(self):
+        def foo(): yield
+
+        self.assertFalse(asyncio.iscoroutine(foo()))
+
+
     def test_iscoroutinefunction(self):
         async def foo(): pass
         self.assertTrue(asyncio.iscoroutinefunction(foo))

Misc/NEWS.d/next/Library/2023-03-16-08-17-29.gh-issue-102748.WNACpI.rst

@@ -0,0 +1,3 @@
+:func:`asyncio.iscoroutine` now returns ``False`` for generators as
+:mod:`asyncio` does not support legacy generator-based coroutines.
+Patch by Kumar Aditya.