[BUG] Cannot inspect cythonized generator functions as such (`co_flags` don't have `CO_GENERATOR`)

Describe the bug Generator functions lose inspection after compiling

To Reproduce Code to reproduce the behaviour:

def func():
    yield 1

when uncompiled:

In [1]: import inspect

In [2]: inspect.isgenerator(func())
Out[2]: True

In [3]: inspect.isgeneratorfunction(func)
Out[3]: True

In [4]: func.__code__.co_flags
Out[4]: 16777315

after being cythonized

In [3]: inspect.isgenerator(func())
Out[3]: True

In [4]: inspect.isgeneratorfunction(func)
Out[4]: False

In [5]: func.__code__.co_flags
Out[5]: 67

In [6]: type(func())
Out[6]: <class '_cython_3_0_0a10.generator'>

Expected behavior Im not sure if this type of inspection is possible with cython_function_or_method, but I was hoping to be able to tell if a given function is a generatorfunction or not

Environment (please complete the following information):

• OS: tested on mac and linux
• Python version tested on 3.9 and 3.10
• Cython version [e.g. 3_0_0a10]

Additional context Add any other context about the problem here.

[scoder]

I looked through the usages of CO_COROUTINE in CPython (main) and they look safe, except for this one, which I don’t quite understand yet:

https://github.com/python/cpython/blob/50b9a7762f06335277d9962edc8d39498601a4e4/Objects/frameobject.c#L208-L211

All other usages only occur for Python generator and coroutine objects, not for other objects that look like coroutines.

[scoder]

That code’s for checking if it’s legal to set the frame)s f_lineno. While tracing you can do that to jump execution around, but you can’t do it into/out of loops, exception blocks and some other things.

Thanks for looking through that.

Since Cython always has a blank co_code, I think it’ll always fail here in the setter so it’s not a problem. Maybe there should be a test for this though.

I wouldn’t rely on that. Cython’s code objects aren’t as blank as they may seem, we emulate quite a bit of Python functionality in them for introspection. A test seems needed, as you wrote.