coverage seems to cause coroutines to skip over exeption handlers on 3.12

[graingert]

urllib3/urllib3#3049 (comment)

Describe the bug
when running on 3.12b1 and coverage 7.2.7 (with C extension) coverage seems to cause coroutines to skip over exeption handlers

To Reproduce
How can we reproduce the problem? Please be specific. Don't link to a failing CI job. Answer the questions below:

1. What version of Python are you using? 3.12b1
2. What version of coverage.py shows the problem? The output of coverage debug sys is helpful. 7.2.7
3. What versions of what packages do you have installed? The output of pip freeze is helpful.
4. What code shows the problem? Give us a specific commit of a specific repo that we can check out. If you've already worked around the problem, please provide a commit before that fix. Python 3.12 Support urllib3/urllib3#3049 (comment)

input:

import asyncio

async def inner():
    loop = asyncio.get_running_loop()
    fut = loop.create_future()
    loop.call_later(0.1, fut.set_exception, Exception())
    try:
        await fut
    except Exception:
        print("good")

async def main():
    await inner()

asyncio.run(main())

Expected behavior

 graingert@conscientious  ~/projects/urllib3   py3-12-debug ± ./.nox/test-3-12/bin/coverage run -m demo
Traceback (most recent call last):
  File "/home/graingert/projects/urllib3/demo.py", line 15, in <module>
    asyncio.run(main())
  File "/usr/lib/python3.12/asyncio/runners.py", line 194, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/asyncio/base_events.py", line 664, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/home/graingert/projects/urllib3/demo.py", line 13, in main
    await inner()
Exception
 ✘  graingert@conscientious  ~/projects/urllib3   py3-12-debug ± vim demo.py 
 graingert@conscientious  ~/projects/urllib3   py3-12-debug ± ./.nox/test-3-12/bin/python -m demo
good

Additional context
Add any other context about the problem here.

[graingert]

eliminating asyncio:

import types

@types.coroutine
def _async_yield(v):
    return (yield v)

async def inner():
    try:
        await _async_yield(None)
    except Exception:
        print("good")
    return "good2"

async def main():
    return await inner()

def run(coro):
    coro.send(None)
    try:
        coro.throw(Exception)
    except StopIteration as e:
        print(e.value)


run(main())

 graingert@conscientious  ~/projects/urllib3   py3-12-debug ± ./.nox/test-3-12/bin/coverage run -m demo
Traceback (most recent call last):
  File "/home/graingert/projects/urllib3/demo.py", line 25, in <module>
    run(main())
  File "/home/graingert/projects/urllib3/demo.py", line 20, in run
    coro.throw(Exception)
  File "/home/graingert/projects/urllib3/demo.py", line 15, in main
    return await inner()
           ^^^^^^^^^^^^^
Exception
 ✘  graingert@conscientious  ~/projects/urllib3   py3-12-debug ± ./.nox/test-3-12/bin/python -m demo      
good
good2

[graingert]

same with a plain generator:

def inner():
    try:
        yield None
    except Exception:
        print("good")
    return "good2"

def main():
    return (yield from inner())

def run(coro):
    coro.send(None)
    try:
        coro.throw(Exception)
    except StopIteration as e:
        print(e.value)


run(main())

 graingert@conscientious  ~/projects/urllib3   py3-12-debug ± ./.nox/test-3-12/bin/coverage run -m demo
Traceback (most recent call last):
  File "/home/graingert/projects/urllib3/demo.py", line 19, in <module>
    run(main())
  File "/home/graingert/projects/urllib3/demo.py", line 14, in run
    coro.throw(Exception)
  File "/home/graingert/projects/urllib3/demo.py", line 9, in main
    return (yield from inner())
            ^^^^^^^^^^^^^^^^^^
Exception
 ✘  graingert@conscientious  ~/projects/urllib3   py3-12-debug ± ./.nox/test-3-12/bin/python -m demo      
good
good2

[sethmlarson]

I'm also able to reproduce this on Ubuntu w/ Python 3.12.0-beta1:

(venv) $ python --version
Python 3.12.0b1

(venv) $ python -m pip freeze
coverage==7.2.7

(venv) $ coverage run -m demo
Traceback (most recent call last):
  File "/tmp/demo.py", line 19, in <module>
    run(main())
  File "/tmp/demo.py", line 14, in run
    coro.throw(Exception)
  File "/tmp/demo.py", line 9, in main
    return (yield from inner())
            ^^^^^^^^^^^^^^^^^^
Exception

(venv) $ python -m demo
good
good2

[graingert]

same issue using a manually written Inner generator:

class Inner:
    def send(self, v):
        return None

    def __iter__(self):
        return self

    def __next__(self):
        return self.send(None)

    def throw(self, *exc_info):
        raise StopIteration("good")


def main():
    return (yield from Inner())

def run(coro):
    coro.send(None)
    try:
        coro.throw(Exception)
    except StopIteration as e:
        print(e.value)


run(main())

[graingert]

eliminating coverage:

./.nox/test-3-12/bin/python -m trace --count -C . demo.py
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/usr/lib/python3.12/trace.py", line 741, in <module>
    main()
  File "/usr/lib/python3.12/trace.py", line 729, in main
    t.runctx(code, globs, globs)
  File "/usr/lib/python3.12/trace.py", line 451, in runctx
    exec(cmd, globals, locals)
  File "demo.py", line 26, in <module>
    run(main())
  File "demo.py", line 21, in run
    coro.throw(Exception)
  File "demo.py", line 16, in main
    return (yield from Inner())
            ^^^^^^^^^^^^^^^^^^
Exception

[pquentin]

This turned out to be a CPython issue, so I think this can be safely closed.

[graingert]

Closed, there's a CPython fix proposed already!

python/cpython#105162