get awaiter stack in pure Python

cstack.py

import asyncio

from asyncio.tasks import Task


def _get_coro_awaiter(coro):
    if hasattr(coro, "cr_await"):
        awaiter = coro.cr_await
        if hasattr(awaiter, "cr_await"):
            return awaiter
    return None


def get_await_stack(coro):
    """Return the chain of coroutines reachable from coro via its awaiter"""
    stack = []
    awaiter = _get_coro_awaiter(coro)
    while awaiter is not None:
        stack.append(awaiter)
        awaiter = _get_coro_awaiter(awaiter)
    return stack


async def f1():
    return await f2()


async def f2():
    # Create a new task for f3()
    return await asyncio.ensure_future(f3())
    # return await f3()


async def f3():
    return await f3a()


async def f3a():
    return await f4()


def dump_task_stack():
    print("Stack retrieved from Task.get_stack():")
    stack = asyncio.current_task().get_stack()
    for frame in stack:
        print(f"  {frame.f_code.co_name}")


async def dump_await_stack():
    print("Stack retrieved using awaiters:")
    coro = asyncio.current_task()._coro
    async def dummy_coro():
        stack = [coro] + get_await_stack(coro)[:-1]
        return stack
    dummy_task = asyncio.create_task(dummy_coro())
    stack = await dummy_task
    for coro in reversed(stack):
        print(f"  {coro.cr_code.co_name}")


async def f4():
    await asyncio.sleep(1)
    dump_task_stack()
    await dump_await_stack()
    return 42


if __name__ == "__main__":
    asyncio.run(f1())