go back to using nest_asyncio for run_sync utility

jupyter_core/utils/__init__.py

@@ -2,12 +2,10 @@
 # Distributed under the terms of the Modified BSD License.
 
 import asyncio
-import atexit
 import errno
 import inspect
 import os
 import sys
-import threading
 import warnings
 from pathlib import Path
 from types import FrameType
@@ -92,43 +90,6 @@ def deprecation(message: str, internal: Union[str, List[str]] = "jupyter_core/")
 T = TypeVar("T")
 
 
-class _TaskRunner:
-    """A task runner that runs an asyncio event loop on a background thread."""
-
-    def __init__(self):
-        self.__io_loop: Optional[asyncio.AbstractEventLoop] = None
-        self.__runner_thread: Optional[threading.Thread] = None
-        self.__lock = threading.Lock()
-        atexit.register(self._close)
-
-    def _close(self):
-        if self.__io_loop:
-            self.__io_loop.stop()
-
-    def _runner(self):
-        loop = self.__io_loop
-        assert loop is not None  # noqa
-        try:
-            loop.run_forever()
-        finally:
-            loop.close()
-
-    def run(self, coro):
-        """Synchronously run a coroutine on a background thread."""
-        with self.__lock:
-            name = f"{threading.current_thread().name} - runner"
-            if self.__io_loop is None:
-                self.__io_loop = asyncio.new_event_loop()
-                self.__runner_thread = threading.Thread(target=self._runner, daemon=True, name=name)
-                self.__runner_thread.start()
-        fut = asyncio.run_coroutine_threadsafe(coro, self.__io_loop)
-        return fut.result(None)
-
-
-_runner_map = {}
-_loop_map = {}
-
-
 def run_sync(coro: Callable[..., Awaitable[T]]) -> Callable[..., T]:
     """Wraps coroutine in a function that blocks until it has executed.
 
@@ -147,23 +108,24 @@ def run_sync(coro: Callable[..., Awaitable[T]]) -> Callable[..., T]:
         raise AssertionError
 
     def wrapped(*args, **kwargs):
-        name = threading.current_thread().name
-        inner = coro(*args, **kwargs)
         try:
-            # If a loop is currently running in this thread,
-            # use a task runner.
-            asyncio.get_running_loop()
-            if name not in _runner_map:
-                _runner_map[name] = _TaskRunner()
-            return _runner_map[name].run(inner)
+            loop = asyncio.get_running_loop()
         except RuntimeError:
-            pass
-
-        # Run the loop for this thread.
-        if name not in _loop_map:
-            _loop_map[name] = asyncio.new_event_loop()
-        loop = _loop_map[name]
-        return loop.run_until_complete(inner)
+            # Workaround for bugs.python.org/issue39529.
+            try:
+                loop = asyncio.get_event_loop_policy().get_event_loop()
+            except RuntimeError:
+                loop = asyncio.new_event_loop()
+                asyncio.set_event_loop(loop)
+        from jupyter_core.utils import patched_nest_asyncio
+
+        patched_nest_asyncio.apply(loop)
+        future = asyncio.ensure_future(coro(*args, **kwargs), loop=loop)
+        try:
+            return loop.run_until_complete(future)
+        except BaseException as e:
+            future.cancel()
+            raise e
 
     wrapped.__doc__ = coro.__doc__
     return wrapped

jupyter_core/utils/patched_nest_asyncio.py

@@ -0,0 +1,54 @@
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+# Note: copied from https://github.com/ipyflow/ipyflow/blob/8e4bc5cb8d4231b9b69f4f9dce867b8101164ac5/core/ipyflow/kernel/patched_nest_asyncio.py
+import asyncio
+import sys
+
+
+def apply(loop=None):
+    import nest_asyncio
+
+    # ref: https://github.com/erdewit/nest_asyncio/issues/14
+    nest_asyncio._patch_task = _patched_patch_task
+
+    # ref: https://github.com/erdewit/nest_asyncio
+    nest_asyncio.apply(loop=loop)
+
+
+def _patched_patch_task():
+    """Patch the Task's step and enter/leave methods to make it reentrant."""
+
+    def step(task, exc=None):
+        curr_task = curr_tasks.get(task._loop)
+        try:
+            step_orig(task, exc)
+        finally:
+            if curr_task is None:
+                curr_tasks.pop(task._loop, None)
+            else:
+                curr_tasks[task._loop] = curr_task
+
+    Task = asyncio.Task
+    if sys.version_info >= (3, 7, 0):
+
+        def enter_task(loop, task):
+            curr_tasks[loop] = task
+
+        def leave_task(loop, task):
+            curr_tasks.pop(loop, None)
+
+        asyncio.tasks._enter_task = enter_task
+        asyncio.tasks._leave_task = leave_task
+        curr_tasks = asyncio.tasks._current_tasks
+    else:
+        curr_tasks = Task._current_tasks
+    try:
+        step_orig = Task._Task__step
+        Task._Task__step = step
+    except AttributeError:
+        try:
+            step_orig = Task.__step
+            Task.__step = step
+        except AttributeError:
+            step_orig = Task._step
+            Task._step = step

pyproject.toml

@@ -17,6 +17,7 @@ classifiers = [
 ]
 requires-python = ">=3.8"
 dependencies = [
+  "nest_asyncio",
   "platformdirs>=2.5",
   "traitlets>=5.3",
   "pywin32>=300 ; sys_platform == 'win32' and platform_python_implementation != 'PyPy'"