exc_info simplifications

[iritkatriel]

I'm trying to understand what it would take to make it possible to write (new) python code without knowing what (type, val, tb) is. This is my current draft.

I don't expect this to make python much faster, but it's the obvious followup to #106.

[gvanrossum]

Sounds good, let's do it.

[iritkatriel]

I started the easy ones:

sys.exception(): https://bugs.python.org/issue46328
PyErr_GetActiveException/PyErr_SetActiveException: https://bugs.python.org/issue46343

[JelleZijlstra]

I opened https://bugs.python.org/issue46330 about the hard one, __exit__. I'd be interested in working with you to find the right approach to the migration. (For what it's worth, I'm skeptical that your suggested introspection approach will be sufficient, since there are likely to be non-introspectable __exit__ methods out in the wild.)

[iritkatriel]

Possibly because sys.excepthook is expected to be called by user code and the profile function not?

[gvanrossum]

But if there was a setter, there could be a getter, and you could call it that way. The docs are not so clear.

I just hope that for the new API we'll use getter and setter functions.

[iritkatriel]

I wonder if we should perhaps defer the excepthook replacement for the future, because

1. It's not just sys.excepthook, there is also threading.excepthook.

2. the new APIs probably won't use used until all supported versions have the reduced exc_info (i.e., 3.11 is the earliest supported version) and in the meantime it's a messy API. (excepthook + exceptionhook + unraisablehook + the threading equivalents).

[iritkatriel]

Also, since we concluded that the interpreter and the stdlib and the rest of the world will need to continue forever calling excepthook (which calls the new API), the benefit of this whole thing is questionable.

[gvanrossum]

Right, let's not rock this particular boat.

[markshannon]

Let's just leave __exit__ as it is.
Changing it is going to be painful and there is no advantage to be gained in terms of performance.
Many context managers don't care if an exception has been raised, so changing from def __exit__(*args): to def __exit__(arg): gains little in terms of usability.