René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"TaskGroup fails to cancel tasks pending creation, if that task starts a failing task","articleBody":"# Bug report\r\n\r\n### Bug description:\r\n\r\nthis 'deadlocks' on eager tasks, but raises an EG as expected on regular 'lazy' tasks.\r\n\r\n```python\r\nimport sys\r\nimport asyncio\r\n\r\n\r\nif sys.version_info \u003e= (3, 13):\r\n    from asyncio import EventLoop\r\nelif sys.platform == \"win32\":\r\n    from asyncio import ProactorEventLoop as EventLoop\r\nelse:\r\n    from asyncio import SelectorEventLoop as EventLoop\r\n\r\n\r\ndef loop_factory():\r\n    loop = EventLoop()\r\n    loop.set_task_factory(asyncio.eager_task_factory)\r\n    return loop\r\n\r\n\r\nasync def main():\r\n    async with asyncio.TaskGroup() as tg:\r\n        async def third_task():\r\n            raise RuntimeError(\"third task failed\")\r\n\r\n        async def second_task():\r\n            tg.create_task(third_task())\r\n            await asyncio.Event().wait()\r\n\r\n        tg.create_task(second_task())\r\n\r\n# asyncio.run(main())\r\nasyncio.run(main(), loop_factory=loop_factory)\r\n```\r\n\r\n\r\n### CPython versions tested on:\r\n\r\n3.12, 3.13, 3.14\r\n\r\n### Operating systems tested on:\r\n\r\nLinux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-128551\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/graingert","@type":"Person","name":"graingert"},"datePublished":"2025-01-06T15:52:23.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/128550/cpython/issues/128550"}