Repository navigation
Some failures in whats_left.sh: method inheritance not as expected #2732
Description
Feature
The whats_left.sh script generates a list of incompatibilities by comparing signatures with inspect.signature(). I think one source of mismatches is because of how builtin object inherit (or don't inherit) from object. I don't yet understand how RustPython is doing this so I'm documenting the issue here, but I could write a PR with some help.
Description
As an example: sys.__loader__ is listed by whats_left because signature() returns a ValueError. The CPython signature is (), which is the default signature of object.
In both CPython and RustPython inspect.signature is calling inspect._signature_from_callable() (code), which eventually gets to this block.
The class is an instance of _frozen_importlib.BuiltinImporter which has no __init__ or __new__ method defined. In CPython, both of those methods are the same as the object methods (using the is test, e.g. the same memory address). In RustPython the __new__ method is different. I would guess that something about the class definition is creating a separate __new__ method even though there shouldn't be one.
Activity
youknowone commentedon Aug 4, 2021
@jamestwebber is this fixed by your PRs?
jamestwebber commentedon Aug 4, 2021
Unfortunately no, I just collapse the error into a single message.
In the case of
__loader__the same message showed up many times because every built-in module had a__loader__instance that came from_frozen_importlib. So my PRs turn that into one message but the underlying cause is still there.moreal commentedon Aug 14, 2021
I resolved #2869 so I believe this issue is also resolved as I understood. To prove this issue is resolved, I executed
./whats_left.shand looked upsys.__loader__but I couldn't. But I can't feel sure that this issue was resolved, could you check it? @jamestwebberjamestwebber commentedon Aug 14, 2021
Yes, this is fixed! The messages were no longer output by
whats_leftbecause in #2760 I tweaked the code to remove items defined in other modules (in retrospect perhaps this was too broad, as there are no examples of__loader__left to check). But I verified the change in behavior which fixes this issue:This has uncovered a new issue: in CPython,
inspect.signature(object)will return()but RustPython raises a ValueError. I think this is a different problem though.jamestwebber commentedon Aug 14, 2021
Oh, the underlying issue is now #2410 which you're already working on 🎉