sys.monitoring `PY_YIELD` leaks internal `async_generator_wrapped_value` object
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Description
Bug report
Bug description:
Rather than the actual value, sys.monitoring's PY_YIELD event passes in to the callback the internal async_generator_wrapped_value.
I imagine this is a bug... it's inconsistent with what it does for non-async generators.
import sys
import types
import typing
import asyncio
async def gen():
yield 42
async def main():
async for _ in gen():
pass
def handle_yield(code: types.CodeType, offset: int, value: object) -> typing.Any:
if code.co_filename == __file__:
print(f"yield name={code.co_qualname} {type(value)=}")
sysmon = sys.monitoring
sysmon.use_tool_id(4, "r")
sysmon.register_callback(4, sysmon.events.PY_YIELD, handle_yield)
sysmon.set_events(4, sysmon.events.PY_YIELD)
asyncio.run(main())
This prints out:
yield name=gen type(value)=<class 'async_generator_wrapped_value'>
CPython versions tested on:
3.12, 3.13, 3.14
Operating systems tested on:
macOS, Linux
Linked PRs
- gh-129031
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by running the provided sys.monitoring PY_YIELD reproduction across the affected CPython versions and inspect the callback behavior for async generators. Review linked PR gh-129031 for the current implementation direction; done means the callback receives the yielded value rather than the internal async_generator_wrapped_value object, with coverage for this case.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- tooling
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100