gh-93297: Make asyncio task groups prevent child tasks from being GCed (#93299)

Author: 1st1

Lib/asyncio/taskgroups.py

@@ -3,8 +3,6 @@
 
 __all__ = ["TaskGroup"]
 
-import weakref
-
 from . import events
 from . import exceptions
 from . import tasks
@@ -19,8 +17,7 @@ def __init__(self):
  self._loop = None
  self._parent_task = None
  self._parent_cancel_requested = False
- self._tasks = weakref.WeakSet()
- self._unfinished_tasks = 0
+ self._tasks = set()
  self._errors = []
  self._base_error = None
  self._on_completed_fut = None
@@ -29,8 +26,6 @@ def __repr__(self):
  info = ['']
  if self._tasks:
  info.append(f'tasks={len(self._tasks)}')
- if self._unfinished_tasks:
- info.append(f'unfinished={self._unfinished_tasks}')
  if self._errors:
  info.append(f'errors={len(self._errors)}')
  if self._aborting:
@@ -93,7 +88,7 @@ async def __aexit__(self, et, exc, tb):
  # can be cancelled multiple times if our parent task
  # is being cancelled repeatedly (or even once, when
  # our own cancellation is already in progress)
- while self._unfinished_tasks:
+ while self._tasks:
  if self._on_completed_fut is None:
  self._on_completed_fut = self._loop.create_future()
 
@@ -114,7 +109,7 @@ async def __aexit__(self, et, exc, tb):
 
  self._on_completed_fut = None
 
- assert self._unfinished_tasks == 0
+ assert not self._tasks
 
  if self._base_error is not None:
  raise self._base_error
@@ -141,15 +136,14 @@ async def __aexit__(self, et, exc, tb):
  def create_task(self, coro, *, name=None, context=None):
  if not self._entered:
  raise RuntimeError(f"TaskGroup {self!r} has not been entered")
- if self._exiting and self._unfinished_tasks == 0:
+ if self._exiting and not self._tasks:
  raise RuntimeError(f"TaskGroup {self!r} is finished")
  if context is None:
  task = self._loop.create_task(coro)
  else:
  task = self._loop.create_task(coro, context=context)
  tasks._set_task_name(task, name)
  task.add_done_callback(self._on_task_done)
- self._unfinished_tasks += 1
  self._tasks.add(task)
  return task
 
@@ -169,10 +163,9 @@ def _abort(self):
  t.cancel()
 
  def _on_task_done(self, task):
- self._unfinished_tasks -= 1
- assert self._unfinished_tasks >= 0
+ self._tasks.discard(task)
 
- if self._on_completed_fut is not None and not self._unfinished_tasks:
+ if self._on_completed_fut is not None and not self._tasks:
  if not self._on_completed_fut.done():
  self._on_completed_fut.set_result(True)
 

Misc/NEWS.d/next/Library/2022-05-27-13-18-18.gh-issue-93297.e2zuHz.rst

@@ -0,0 +1 @@
+Make asyncio task groups prevent child tasks from being GCed