Plugin to add generated members

[e4lam]

Question

Hi, I'm trying to write a plugin for generated members for our pybind11 classes (ie. C extension module) and seeking advice on the best way to go about it. In our code, we have an extends_class decorator like this:

def extends_class(cls):
    def decorator(f):
        setattr(cls, f.__name__, f)
    return decorator

So to add an generated member onto our pybind11 class, we do something like this:

from my_module import Foo
class FooExtension:
    @extends_class(Foo)
    def foobar(self):
        # do stuff

So I thought what I could do was write a plugin that finds the @extends_class(Foo) and then assign the decorated function into the ClassDef node for Foo. I got as far in my plugin to getting the decorated function node but then I couldn't figure out how to get at the ClassDef node for Foo. I can find the ImportFrom node for Foo (via the node root() method) but from there, I can't seem to find where the actual ast node tree is for my_module. Can you point me in the direction from here?

Looking at some of the astroid brain code, it seems that in some cases there's a different mechanism for this where it uses inference_tip() transform plugin instead. But I'm not sure if I can do that for this particular setup?

Any advice please? Thank you in advance!

Documentation for future user

It would be good if a lot more details about different techniques could be provided in the "Transform plugins" chapter of the "How To Guides".

Additional context

No response

[Pierre-Sassoulas]

Thank you for opening the issue. The modern way to do this would probably be to improve pyi support in astroid/pylint then create the pyi. The pyi could also be used in type checkers. We don't have nothing for pyi but we don't have something usable at the moment (we detect them and can parse them but we still need to merge them properly with existing code if we have both). Or you could create an astroid brain (some understandable dumbed down code that astroid can parse for the part it fails to parse). Generated members are the last resort on the user side when there's no brain in astroid.

[e4lam]

Thanks for the response, but if I add a brain, then I'm still in the same boat as I don't know how to make it do what I want because there doesn't seem access to the already parsed tree of C extension. Do you know how one should do that if writing a brain?

Or do you mean I should hard code the generated members in the brain/plugin instead of trying to determine the members from the code being parsed?

[Pierre-Sassoulas]

Yes astroid brain are hardcoded from the API of something that can't be parsed (using the doc or your understanding, or automatically from the parsed C....). It's like generated member but you can use python to do more complex things than with generated member.