Issue 39764: PyAsyncGenObject causes task.get_stack() raising AttributeError

This issue exists since 3.6.

The implementation of get stack on Task is looking for two attribute [1]: "cr_frame" for coroutines, "gi_frame" for generators (legacy coroutines). However, PyAsyncGenObject provides none of them but "ag_frame" [2].

Fix PR: https://github.com/python/cpython/pull/18669

A simple reproduce:

    def test_async_gen_aclose_compatible_with_get_stack(self):
        async def async_generator():
            yield object()

        async def run():
            ag = async_generator()
            asyncio.create_task(ag.aclose())
            tasks = asyncio.all_tasks()
            for task in tasks:
                # No AttributeError raised
                task.get_stack()

        self.loop.run_until_complete


I found this in my project I want to view who created the Tasks.

[1] https://github.com/python/cpython/blob/21da76d1f1b527d62b2e9ef79dd9aa514d996341/Lib/asyncio/base_tasks.py#L27
[2] https://github.com/python/cpython/blob/21da76d1f1b527d62b2e9ef79dd9aa514d996341/Objects/genobject.c#L1329

New changeset 4482337decdbd0c6e2150346a68b3616bda664aa by Lidi Zheng in branch 'master':
bpo-39764: Make Task.get_stack accept ag_frame (#18669)
https://github.com/python/cpython/commit/4482337decdbd0c6e2150346a68b3616bda664aa

New changeset 43932dc1eaf36d75b2ee0420d8be747001315c26 by Miss Islington (bot) in branch '3.8':
bpo-39764: Make Task.get_stack accept ag_frame (GH-18669)
https://github.com/python/cpython/commit/43932dc1eaf36d75b2ee0420d8be747001315c26

pull_requests: + pull_request18097
stage: patch review