gh-94912: Added marker for non-standard coroutine function detection

Doc/library/inspect.rst

@@ -358,6 +358,20 @@ attributes:
       wrapped function is a :term:`coroutine function`.
 
 
+.. function:: markcoroutinefunction(object)
+
+   Decorator to mark a callable as a :term:`coroutine function` if it would not
+   otherwise be detected by :func:`iscoroutinefunction`.
+
+   This may be of use for sync functions that return an awaitable or objects
+   implementing an :keyword:`async def` ``__call__``.
+
+   Prefer :keyword:`async def` functions or calling the function and testing
+   the return with :func:`isawaitable` where feasible.
+
+   .. versionadded:: 3.12
+
+
 .. function:: iscoroutine(object)
 
    Return ``True`` if the object is a :term:`coroutine` created by an

Lib/inspect.py

@@ -125,6 +125,7 @@
     "ismodule",
     "isroutine",
     "istraceback",
+    "markcoroutinefunction",
     "signature",
     "stack",
     "trace",
@@ -391,12 +392,23 @@ def isgeneratorfunction(obj):
     See help(isfunction) for a list of attributes."""
     return _has_code_flag(obj, CO_GENERATOR)
 
+def markcoroutinefunction(func):
+    """
+    Decorator to ensure callable is recognised as a coroutine function.
+    """
+    func.__code__ = func.__code__.replace(
+        co_flags=func.__code__.co_flags | CO_COROUTINE
+    )
+    return func
+
 def iscoroutinefunction(obj):
     """Return true if the object is a coroutine function.
 
     Coroutine functions are defined with "async def" syntax.
     """
-    return _has_code_flag(obj, CO_COROUTINE)
+    return _has_code_flag(obj, CO_COROUTINE) or (
+        not isclass(obj) and callable(obj) and _has_code_flag(obj.__call__, CO_COROUTINE)
+    )
 
 def isasyncgenfunction(obj):
     """Return true if the object is an asynchronous generator function.

Lib/test/test_inspect.py

@@ -202,6 +202,30 @@ def test_iscoroutine(self):
                     gen_coroutine_function_example))))
         self.assertTrue(inspect.isgenerator(gen_coro))
 
+        async def _fn3():
+            pass
+
+        @inspect.markcoroutinefunction
+        def fn3():
+            return _fn3()
+
+        self.assertTrue(inspect.iscoroutinefunction(fn3))
+
+        class Cl:
+            async def __call__(self):
+                pass
+
+        self.assertFalse(inspect.iscoroutinefunction(Cl))
+        self.assertTrue(inspect.iscoroutinefunction(Cl()))
+
+        class Cl2:
+            @inspect.markcoroutinefunction
+            def __call__(self):
+                pass
+
+        self.assertFalse(inspect.iscoroutinefunction(Cl2))
+        self.assertTrue(inspect.iscoroutinefunction(Cl2()))
+
         self.assertFalse(
             inspect.iscoroutinefunction(unittest.mock.Mock()))
         self.assertTrue(

Misc/NEWS.d/next/Library/2022-11-17-10-02-18.gh-issue-94912.G2aa-E.rst

@@ -0,0 +1 @@
+Added ``@markcoroutinefunction`` decorator to ``inspect`` module.