do we need to worry about nesting of greenlet_spawn / await_()? seems like not

foo.py

import asyncio
import contextvars
import sys

import greenlet


current_greenlet_context = contextvars.ContextVar("current greenlet context")


def await_(coroutine):
    current_greenlet = current_greenlet_context.get()
    if current_greenlet is None:
        raise Exception(
            "not running inside a greenlet right now, "
            "can't use await_() function"
        )
    return current_greenlet.switch(coroutine)


async def greenlet_spawn(fn, *args):

    result_future = asyncio.Future()

    def run_greenlet_target():
        result_future.set_result(fn(*args))
        return None

    async def run_greenlet():
        gl = greenlet.greenlet(run_greenlet_target)
        greenlet_coroutine = gl.switch()

        while greenlet_coroutine is not None:
            task = asyncio.create_task(greenlet_coroutine)
            try:
                await task
            except:
                # this allows an exception to be raised within
                # the moderated greenlet so that it can continue
                # its expected flow.
                greenlet_coroutine = gl.throw(*sys.exc_info())
            else:
                greenlet_coroutine = gl.switch(task.result())

    current_greenlet = greenlet.greenlet(run_greenlet)

    print("set greenlet context to: %s" % run_greenlet)
    current_greenlet_context.set(current_greenlet)
    try:
        await current_greenlet.switch()
    finally:
        # make sure the context is what we set it to, testing
        # that a nested call has no issue
        assert current_greenlet_context.get() is current_greenlet
        print("reset greenlet context None from: %s" % run_greenlet)
        current_greenlet_context.set(None)

    return result_future.result()


async def func1():
    print("func1")
    await greenlet_spawn(func2)


def func2():
    print("func2")
    await_(func3())


async def func3():
    print("func3")
    await greenlet_spawn(func4)


def func4():
    print("func4")
    await_(asyncio.sleep(1))


asyncio.run(func1())

output:

$ python test4.py 
func1
set greenlet context to: <function greenlet_spawn.<locals>.run_greenlet at 0x7f8573f94a60>
func2
func3
set greenlet context to: <function greenlet_spawn.<locals>.run_greenlet at 0x7f8573f94b80>
func4
reset greenlet context None from: <function greenlet_spawn.<locals>.run_greenlet at 0x7f8573f94b80>
reset greenlet context None from: <function greenlet_spawn.<locals>.run_greenlet at 0x7f8573f94a60>