Can't navigate to class method

[f3rn4nd0-c354r]

Type: Bug

Behaviour

Expected vs. Actual

When I CTRL + Click method "retrieve_data" in the last statement of the below code (bank.retrieve_data()), I would expect to go to the method definition, but nothing happens.

Steps to reproduce:

Use the following code:

from abc import ABC
from typing import List, Optional, Type

class Bank(ABC):
    @classmethod
    def recognises(cls):
        raise NotImplemented()

    def retrieve_data(self):
        pass

class B(Bank):
    def retrieve_data(self):
        print("oi")

    @classmethod
    def recognises(cls,):
        return B()

if __name__ == "__main__":
    bank: Optional[Bank] = None
    known_banks: List[Type[Bank]] = [B]
    for current_bank in known_banks:
        bank = current_bank.recognises()

    bank.retrieve_data()

Diagnostic data

• Python version (& distribution if applicable, e.g. Anaconda): 3.11.0
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Global
• Value of the python.languageServer setting: Default

Output for Python in the Output panel (View→Output, change the drop-down the upper-right of the Output panel to Python)

``` XXX ```

User Settings

``` venvPath: "" venvFolders: "" languageServer: "Pylance" ```

Extension version: 2023.22.1 VS Code version: Code 1.85.2 (8b3775030ed1a69b13e4f4c628c612102e30a681, 2024-01-18T06:40:19.222Z) OS version: Linux x64 5.15.0-91-generic snap Modes:

System Info

|Item|Value| |---|---| |CPUs|Intel(R) Core(TM) i7-8650U CPU @ 1.90GHz (8 x 3028)| |GPU Status|2d_canvas: unavailable_software
canvas_oop_rasterization: disabled_off
direct_rendering_display_compositor: disabled_off_ok
gpu_compositing: disabled_software
multiple_raster_threads: enabled_on
opengl: disabled_off
rasterization: disabled_software
raw_draw: disabled_off_ok
video_decode: disabled_software
video_encode: disabled_software
vulkan: disabled_off
webgl: unavailable_software
webgl2: unavailable_software
webgpu: disabled_off| |Load (avg)|2, 2, 3| |Memory (System)|31.20GB (25.48GB free)| |Process Argv|--no-sandbox --force-user-env --unity-launch --crash-reporter-id 4cd79d6f-f1f2-4022-9998-d5c0418d3d8e| |Screen Reader|no| |VM|0%| |DESKTOP_SESSION|plasma| |XDG_CURRENT_DESKTOP|KDE| |XDG_SESSION_DESKTOP|KDE| |XDG_SESSION_TYPE|x11|

A/B Experiments

``` vsliv368cf:30146710 vspor879:30202332 vspor708:30202333 vspor363:30204092 vswsl492cf:30256860 vscod805:30301674 binariesv615:30325510 vsaa593:30376534 py29gd2263:30899288 vsclangdc:30486549 c4g48928:30535728 azure-dev_surveyone:30548225 2i9eh265:30646982 962ge761:30933248 pythongtdpath:30769146 welcomedialog:30910333 pythonidxpt:30866567 pythonnoceb:30805159 asynctok:30898717 pythontestfixt:30902429 pythonregdiag2:30936856 pyreplss1:30897532 pythonmypyd1:30879173 pythoncet0:30885854 pythontbext0:30879054 accentitlementsc:30887149 dsvsc016:30899300 dsvsc017:30899301 dsvsc018:30899302 dsvsc019acf:30933242 ```

[debonte]

There are two issues:

1. Pylance thinks that all implementations of Bank.recognises will return NoReturn (i.e. they all raise an error).

You can fix this by giving Bank.recognises a return annotation of "Bank":

class Bank(ABC):
    @classmethod
    def recognises(cls) -> "Bank":
        raise NotImplemented()

Btw, you may also have intended to decorate Bank.recognises with @abstractmethod:

from abc import ABC, abstractmethod

class Bank(ABC):
    @classmethod
    @abstractmethod
    def recognises(cls) -> "Bank":
        raise NotImplemented()

2. After making the change above, go to definition will work on retrieve_data but you'll see a diagnostic: "retrieve_data" is not a known member of "None".

Although it's obvious to humans, Pylance doesn't know that after the for loop, bank is guaranteed to be non-None.

This is by design. There's a short explanation of why here.

You can work around this by testing bank after the loop:

    if bank:
        bank.retrieve_data()

Btw, you probably want to be raising NotImplementedError rather than the NotImplemented singleton.

[f3rn4nd0-c354r]

Hi! Thanks for all the details and for helping me improve my code. Replacing NotImplemented by NotImplementedError was enought, no need to add the test. By added the other suggestions. Thanks!