gh-108901: Deprecate inspect.getargs, slate it for removal in 3.15

[sobolevn]

Following the discussion of #108902, I documented that getargs is deprecated (since it is not documented anywhere, I just modified its docstring) and that inspect.signature(types.FunctionType(co,{})) is the modern alternative. I think that it is safe to remove this function in two versions, because it does not work anyway (pos-only, kw-only params are incorrect).

I also don't think that modernizing getargvalues is valuable, because it will also be deprecated in 3.13 and hopefully removed in 3.15 as well.

CC @AlexWaygood@merwok@vstinner who reviewed the first PR.

• Issue: Add modern alternatives to inspect module, deprecate old incorrect APIs #108901

[AlexWaygood]

Maybe we should follow our own advice and use inspect.signature(types.FunctionType(frame.f_code,{})) here? :)

[sobolevn]

I don't think so. Right now getargs does some ugly things:

cpython/Lib/inspect.py

Line 1384 in fef6fb8

returnArguments(args+kwonlyargs, varargs, varkw)

It combines pos_or_kw_args together with kw_only_args, but ignores pos_only_args.

I think that we can just keep it as-is and then remove all of them together in 3.15 (because getargvalues will also be deprecated and removed at the same time, PR is just not ready yet).

[AlexWaygood]

Okay, I see. Maybe we should do the getargvalues() deprecation first, though, in that case? It makes me a little uncomfortable adding this deprecation warning now, if we're not able to make the mandated change in our own code yet.

(I'm fine suppressing DeprecationWarnings in a function that is itself deprecated, but getargvalues() isn't, yet. And I know you plan to work on deprecating it immediately after this PR, but if I had a pound for every time somebody promised me they'd work on something the next day, and then discovered it was harder than they expected, I'd be a rich man :)

[sobolevn]

Sure, I can open a PR about getargvalues() first 👍

[AlexWaygood]

LGTM, thanks! As discussed in https://github.com/python/cpython/pull/112279/files#r1402002908, however, let's deprecate getargvalues() first 👍