`asyncio.print_call_graph()` loses the call stack at asynchronous generators

[deadlovelll]

Bug report

Bug description:

asyncio.print_call_graph() stops at the first async gen in the await chain and silently drops all of the call stack below it

Repro:

import asyncio

async def deep():
    await asyncio.Event().wait()

async def producer():
    await deep()
    yield 1

async def consumer():
    async for _ in producer():
        pass

async def main():
    t = asyncio.create_task(consumer(), name='consumer')
    await asyncio.sleep(0.05)
    print(asyncio.format_call_graph(t))

asyncio.run(main())

Expected:

* Task(name='consumer', id=0x105be89b0)
  + Call stack:
  |   File '/Users/timofeiivankov/cpython/Lib/asyncio/locks.py', line 210, in async Event.wait()
  |   File '/Users/timofeiivankov/cpython/repro.py', line 4, in async deep()
  |   File '/Users/timofeiivankov/cpython/repro.py', line 7, in async generator producer()
  |   File '/Users/timofeiivankov/cpython/repro.py', line 11, in async consumer()

Actual:

* Task(name='consumer', id=0x105b089b0)
  + Call stack:
  |   File '/Users/timofeiivankov/cpython/repro.py', line 11, in async consumer()

Proposed fix: expose the wrapped generator as ag_gen and step over the wrapper through it

Have a fix ready for that

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-156980: Fix asyncio call graph truncation at async generators #156984

[kumaraditya303]

There might be similar issues when iterating over async gen with anext.

[deadlovelll]

There might be similar issues when iterating over async gen with anext.

anext(agen) returns the async_generator_asend, so it is already covered by this fix. But anext(agen, default) is not because it returns anext_awaitable which doesnt expose async gen. Do you want me to create a new issue for that, or push to this one?

[kumaraditya303]

Do you want me to create a new issue for that, or push to this one?

A new issue would be better, I still need to think more about this case and aiter too.

[deadlovelll]

Do you want me to create a new issue for that, or push to this one?

A new issue would be better, I still need to think more about this case and aiter too.

Thanks! I'll do it tomorrow. I can also look into what other cases there might be

[kumaraditya303]

cc @1st1 @pablogsal

[deadlovelll]

@kumaraditya303 hi! just created issue for anext. There are also issue with aiter(callable, stop_value). If you don't mind i can create issue and pr for it, or give you the details if you want to work on it yourself

[kumaraditya303]

You can create issues but wait for creating PR, I haven't decided yet how I want to to fix this and will likely work on this myself.