fix(tasks): use inspect.iscoroutinefunction for Python 3.14 compatibility

asyncio.iscoroutinefunction is deprecated in Python 3.14 and emits a
DeprecationWarning. inspect.iscoroutinefunction is the recommended
replacement and is equivalent on Python 3.12+ (asyncio.coroutine was
removed in 3.12).

Closes #373

Signed-off-by: SAY-5 <say.apm35@gmail.com>

Author: SAY-5

fastapi_utils/tasks.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import asyncio
+import inspect
 import logging
 import warnings
 from functools import wraps
@@ -19,15 +20,15 @@
 
 
 async def _handle_func(func: NoArgsNoReturnAnyFuncT) -> None:
-    if asyncio.iscoroutinefunction(func):
+    if inspect.iscoroutinefunction(func):
         await func()
     else:
         await run_in_threadpool(func)
 
 
 async def _handle_exc(exc: Exception, on_exception: ExcArgNoReturnAnyFuncT | None) -> None:
     if on_exception:
-        if asyncio.iscoroutinefunction(on_exception):
+        if inspect.iscoroutinefunction(on_exception):
             await on_exception(exc)
         else:
             await run_in_threadpool(on_exception, exc)

tests/test_tasks_iscoroutine_regression.py

@@ -0,0 +1,20 @@
+"""Regression tests for issue #373.
+
+The tasks module must use ``inspect.iscoroutinefunction`` rather than
+``asyncio.iscoroutinefunction``, which is deprecated in Python 3.14
+(``DeprecationWarning``) and scheduled for removal.
+
+See: https://github.com/fastapiutils/fastapi-utils/issues/373
+"""
+
+from __future__ import annotations
+
+import inspect
+
+from fastapi_utils import tasks as tasks_module
+
+
+def test_tasks_module_uses_inspect_iscoroutinefunction() -> None:
+    source = inspect.getsource(tasks_module)
+    assert "asyncio.iscoroutinefunction" not in source
+    assert "inspect.iscoroutinefunction" in source