Code completion looses Self return type if method is wrapped with type hinted decorator

[binste]

The issue came up in this PR in the Altair repo were we are trying to improve autocompletion for IDEs such as VS Code as well as Jupyter with installed JupyterLSP and python-lsp-server. The approach suggested in the PR works for VS Code but not for JupyterLSP. Let me know if this is not a Jedi but a python-lsp-server or jupyterlsp issue.

As a large part of the codebase of Altair is auto-generated, the current approach relies on some type hinted decorators. The actual decorator we use is more complex but I tried to reduce it to a minimal reproducible example below. I'm running this on Python 3.9 with newest Jupyterlab, Jupyterlsp, and python-lsp-server[all]:

from typing import Callable
from typing_extensions import Self

def use_signature(Obj):
    def decorate(f: Callable):
        return f
    return decorate

class SignatureClass:
    def __init__(self, arg1, arg2):
        self.arg1 = arg1

class MainClass:
    @use_signature(SignatureClass)
    def returns_self(self, *args, **kwargs) -> Self:
        return self
    
    def another_method(self):
        pass

return_self correctly shows Self as return type:

but it cannot complete `another_method`

When removing Callable from the decorate function it still shows Self as return type and can now complete another_method:

The expected behaviour would be that another_method can be completed even with the Callable annotation, especially as it still is aware of the return type hint Self.

[davidhalter]

Self is currently not supported.