fix: Python 3.14 task

python/cpython#129899

Author: Chaoses-Ib

nest_asyncio.py

@@ -43,7 +43,13 @@ def _get_event_loop(stacklevel=3):
     # Use module level _current_tasks, all_tasks and patch run method.
     if hasattr(asyncio, '_nest_patched'):
         return
-    if sys.version_info >= (3, 6, 0):
+    
+    # Using _PyTask on Python 3.14+ will break current_task() (and all_tasks(),
+    # _swap_current_task())
+    # Even we replace it with _py_current_task(), it only works with _PyTask, but
+    # the external loop is probably using _CTask.
+    # https://github.com/python/cpython/pull/129899
+    if sys.version_info >= (3, 6, 0) and sys.version_info < (3, 14, 0):
         asyncio.Task = asyncio.tasks._CTask = asyncio.tasks.Task = \
             asyncio.tasks._PyTask
         asyncio.Future = asyncio.futures._CFuture = asyncio.futures.Future = \
@@ -127,14 +133,25 @@ def _run_once(self):
             if not handle._cancelled:
                 # preempt the current task so that that checks in
                 # Task.__step do not raise
-                curr_task = curr_tasks.pop(self, None)
+                if sys.version_info < (3, 14, 0):
+                    curr_task = curr_tasks.pop(self, None)
+                else:
+                    # Work with both C and Py
+                    try:
+                        curr_task = asyncio.tasks._swap_current_task(self, None)
+                    except KeyError:
+                        curr_task = None
 
                 try:
                     handle._run()
                 finally:
                     # restore the current task
                     if curr_task is not None:
-                        curr_tasks[self] = curr_task
+                        if sys.version_info < (3, 14, 0):
+                            curr_tasks[self] = curr_task
+                        else:
+                            # Work with both C and Py
+                            asyncio.tasks._swap_current_task(self, curr_task)
 
         handle = None
 

tests/314_task.py

@@ -0,0 +1,31 @@
+# /// script
+# requires-python = ">=3.14"
+# dependencies = [
+#     "nest-asyncio",
+# ]
+#
+# [tool.uv.sources]
+# nest-asyncio = { path = "../", editable = true }
+# ///
+import asyncio
+import nest_asyncio
+
+nest_asyncio.apply()
+
+async def f():
+    print(asyncio.get_running_loop())
+    assert asyncio.get_running_loop() is not None
+
+    print(asyncio.tasks._current_tasks)
+    # assert asyncio.tasks._current_tasks == {}
+
+    print(asyncio.tasks.current_task())
+    assert asyncio.tasks.current_task() is not None
+
+    print(asyncio.tasks._py_current_task())
+    # assert asyncio.tasks._py_current_task() is None
+
+    print(asyncio.tasks._current_tasks)
+    # assert asyncio.tasks._current_tasks == {}
+
+asyncio.run(f())

tests/314_task_mix.py

@@ -0,0 +1,31 @@
+# /// script
+# requires-python = ">=3.14"
+# dependencies = [
+#     "nest-asyncio",
+# ]
+#
+# [tool.uv.sources]
+# nest-asyncio = { path = "../", editable = true }
+# ///
+import asyncio
+import nest_asyncio
+
+async def f():
+    nest_asyncio.apply()
+
+    print(asyncio.get_running_loop())
+    assert asyncio.get_running_loop() is not None
+
+    print(asyncio.tasks._current_tasks)
+    # assert asyncio.tasks._current_tasks == {}
+
+    print(asyncio.tasks.current_task())
+    assert asyncio.tasks.current_task() is not None
+
+    print(asyncio.tasks._py_current_task())
+    # assert asyncio.tasks._py_current_task() is None
+
+    print(asyncio.tasks._current_tasks)
+    # assert asyncio.tasks._current_tasks == {}
+
+asyncio.run(f())

tests/nest_test.py

@@ -1,3 +1,12 @@
+# /// script
+# requires-python = ">=3.5"
+# dependencies = [
+#     "nest-asyncio",
+# ]
+#
+# [tool.uv.sources]
+# nest-asyncio = { path = "../", editable = true }
+# ///
 import asyncio
 import sys
 import unittest

tests/test.ps1

@@ -0,0 +1,42 @@
+pushd tests
+
+# uv run --python 3.5 nest_test.py
+uv run --python 3.8 nest_test.py
+if (!$?) {
+    throw "3.10"
+}
+uv run --python 3.9 nest_test.py
+if (!$?) {
+    throw "3.9"
+}
+uv run --python 3.10 nest_test.py
+if (!$?) {
+    throw "3.10"
+}
+uv run --python 3.11 nest_test.py
+if (!$?) {
+    throw "3.11"
+}
+uv run --python 3.12 nest_test.py
+if (!$?) {
+    throw "3.12"
+}
+uv run --python 3.13 nest_test.py
+if (!$?) {
+    throw "3.13"
+}
+uv run --python 3.14 nest_test.py
+if (!$?) {
+    throw "3.14"
+}
+
+uv run --python 3.14 314_task.py
+if (!$?) {
+    throw "314_task"
+}
+uv run --python 3.14 314_task_mix.py
+if (!$?) {
+    throw "314_task_mix"
+}
+
+popd