René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Cancellation leaks out of asyncio.TaskGroup on 3.12 when using eager tasks","articleBody":"# Bug report\n\n### Bug description:\n\n```python\nimport sys\nimport asyncio\n\nif sys.platform == \"win32\":\n    EventLoop = asyncio.ProactorEventLoop\nelse:\n    EventLoop = asyncio.SelectorEventLoop\n\n\nasync def demo():\n    class MyError(Exception):\n        pass\n\n    async def throw_error():\n        raise MyError\n\n    try:\n        async with asyncio.TaskGroup() as tg:\n            tg.create_task(throw_error())\n    except* MyError:\n        pass\n\n\ndef loop_factory():\n    loop = EventLoop()\n    loop.set_task_factory(asyncio.eager_task_factory)\n    return loop\n\nasyncio.run(demo(), loop_factory=loop_factory)\n```\n\nresults in:\n```pytb\nTraceback (most recent call last):\n  File \"/home/graingert/projects/anyio/demo.py\", line 29, in \u003cmodule\u003e\n    asyncio.run(demo(), loop_factory=loop_factory)\n  File \"/usr/lib/python3.12/asyncio/runners.py\", line 194, in run\n    return runner.run(main)\n           ^^^^^^^^^^^^^^^^\n  File \"/usr/lib/python3.12/asyncio/runners.py\", line 118, in run\n    return self._loop.run_until_complete(task)\n           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/usr/lib/python3.12/asyncio/base_events.py\", line 687, in run_until_complete\n    return future.result()\n           ^^^^^^^^^^^^^^^\nasyncio.exceptions.CancelledError\n```\n\n### CPython versions tested on:\n\n3.12\n\n### Operating systems tested on:\n\nLinux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-129063\n* gh-129089\n* gh-128586\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/graingert","@type":"Person","name":"graingert"},"datePublished":"2025-01-07T13:52:17.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/128588/cpython/issues/128588"}