[Python-checkins] GH-98543: Fix `asyncio.TaskGroup` to not keep reference to errors after raising ExceptionGroup (#98544)

[gvanrossum]

https://github.com/python/cpython/commit/f4a14941e6e54b15012fca067f6a9b2ff29f201a
commit: f4a14941e6e54b15012fca067f6a9b2ff29f201a
branch: main
author: Kumar Aditya <59607654+kumaraditya303 at users.noreply.github.com>
committer: gvanrossum <gvanrossum at gmail.com>
date: 2022-10-22T09:05:11-07:00
summary:

GH-98543: Fix `asyncio.TaskGroup`  to not keep reference to errors after raising ExceptionGroup  (#98544)

files:
M Lib/asyncio/taskgroups.py

diff --git a/Lib/asyncio/taskgroups.py b/Lib/asyncio/taskgroups.py
index 5d5e2a8a85dd..911419e1769c 100644
--- a/Lib/asyncio/taskgroups.py
+++ b/Lib/asyncio/taskgroups.py
@@ -128,11 +128,11 @@ async def __aexit__(self, et, exc, tb):
             # Exceptions are heavy objects that can have object
             # cycles (bad for GC); let's not keep a reference to
             # a bunch of them.
-            errors = self._errors
-            self._errors = None
-
-            me = BaseExceptionGroup('unhandled errors in a TaskGroup', errors)
-            raise me from None
+            try:
+                me = BaseExceptionGroup('unhandled errors in a TaskGroup', self._errors)
+                raise me from None
+            finally:
+                self._errors = None
 
     def create_task(self, coro, *, name=None, context=None):
         if not self._entered: