Python extension does not pickup Nix environment

[GuillaumeDesforges]

Describe the bug
The official Python extension does not pickup the environment provided by the shell.nix.

e.g. my nix-shell has black formatter and flake8 in buildInputs, which I can call from the command line after nix-shell, but VS Code still tells me that black and flake8 are not installed.

To Reproduce
Steps to reproduce the behavior:

1. Create poetry project, e.g. nix-shell -p poetry then poetry init && poetry add -D black
2. Create shell.nix

let
  pkgs = import <nixpkgs> {};
  python-env = pkgs.poetry2nix.mkPoetryEnv {
    projectDir = ./.;
  };
in
  pkgs.mkShell {
    buildInputs = [
      python-env
    ];
  }

3. Start VS Code with Python extension, select shell.nix and reload.
4. Try to format some Python code using black (in VS Code Shift+Alt+F, after setting "python.formatting.provider": "black" in settings)

Expected behavior
VS Code should pickup black from my nix shell

Environment:

• OS: NixOS 20.03
• VS Code:

  Version: 1.51.0-insider
  Commit: fce8fc82cacf0b4e2a18c633b6c6f3058702a5c9
  

• Version: v0.1.2

Additional context
Add any other context about the problem here.

[GuillaumeDesforges]

I looked at the source code. This extension just defines environment variables for the current process.

nix-env-selector/src/env.ts

Lines 5 to 7 in 62fc2e3

	const set = (name: string, value: string | undefined) => {
	process.env[name] = value;
	};

I pushed the issue to upstream.

microsoft/vscode-python#14794