generated code to offer nix-develop as version manager

[Jeffrey04]

Motivation

I was having problem with setting up ruby-lsp with nix develop, and turned to the discussion board #3683 for help. After getting some tips from @vinistock I decided to see if I could submit a patch

Implementation

I am very new to both nix and vscode extension development, so most of the work is done by gemini-cli. From what I can tell, here are the changes:

1. Defining a new version manager type nix-develop
2. (possibly need revision) For now, reuse customRubyCommand to define the directory holding the flake.nix file
3. By referring to vscode/src/ruby/custom.ts, create a version for nixDevelop.ts, that fires the command as follows

`nix develop /Users/jeffrey04/Projects/home-manager/devenvs/ruby-3.3 --command ruby -EUTF-8:UTF-8 '/Users/jeffrey04/.vscode-oss/extensions/shopify.ruby-lsp-0.9.31/activation.rb'

Automated Tests

I need help on this one

Manual Tests

this is my flake.nix

# flake.nix
{
  description = "A cross-platform Ruby development environment";

  # Define the inputs for this flake, primarily nixpkgs.
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
  };

  # Define the outputs of this flake.
  outputs = { self, nixpkgs }:
    let
      # A list of systems we want to support.
      supportedSystems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];

      # A helper function to generate an attribute set for each system.
      forEachSystem = f: nixpkgs.lib.genAttrs supportedSystems (system: f {
        pkgs = nixpkgs.legacyPackages.${system};
        system = system;
      });

    in
    {
      # Generate a `devShell` for each of the `supportedSystems`.
      devShells = forEachSystem ({ pkgs, system }:
      {
        default = pkgs.mkShell {
          # A name for the shell environment.
          name = "ruby-3.3";

          # List of packages to be available in the development environment.
          buildInputs = with pkgs; [
            # fish is kept so that fish-specific completions from other
            # packages can be made available.
            fish
            # Git is needed for fetching gems from git repositories.
            git
            # The Ruby interpreter.
            ruby
            # Bundler for managing Ruby gems.
            bundler
            # Common dependencies for building native extensions.
            cmake
            findutils
            gcc
            gnumake
            # Libraries often required by gems.
            openssl
            pkg-config
            libmysqlclient
            shared-mime-info
            re2
            readline
            zlib
          ] ++ lib.optionals stdenv.isDarwin [
            # Add macOS-specific dependencies.
            libiconv
          ];

          # This hook now correctly detects the parent shell (e.g., fish)
          # and works for both `nix develop` and `direnv`.
          shellHook = ''
            # Ruby-specific setup
            export FREEDESKTOP_MIME_TYPES_PATH="${pkgs.shared-mime-info}/share/mime/packages/freedesktop.org.xml"
            export PATH=$HOME/.local/share/gem/ruby/3.3.0/bin:$PATH
          '';
        };
      });
    };
}

and this is my workspace settings.json

{
  "rubyLsp.rubyVersionManager": {
    "identifier": "nix-develop"
  },
  "rubyLsp.customRubyCommand": "/Users/jeffrey04/Projects/home-manager/devenvs/ruby-3.3"
}

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[Jeffrey04]

I have signed the CLA!