shell.nix

{ }:
let
    pkgs = import (builtins.fetchGit {
        name = "nixpkgs-with-cmake-3.18.2";
        url = "https://github.com/NixOS/nixpkgs/";
        ref = "refs/heads/nixpkgs-unstable";
        rev = "2c162d49cd5b979eb66ff1653aecaeaa01690fcc";
    }) {};

    pkgs_ninja = import (builtins.fetchGit {
        name = "nixpkgs-with-ninja-1.9.0";
        url = "https://github.com/NixOS/nixpkgs/";
        ref = "refs/heads/nixpkgs-unstable";
        rev = "2158ec610d90359df7425e27298873a817b4c9dd";
    }) {};
in
    pkgs.mkShell {
        nativeBuildInputs = [
            pkgs.buildPackages.cowsay
            pkgs.buildPackages.nodejs-12_x  # 12.18.4
            pkgs.buildPackages.yarn         # 1.22.5
            pkgs.buildPackages.ruby         # 2.6.6
            pkgs.buildPackages.watchman     # 4.9.0
            pkgs.buildPackages.cmake        # 3.18.2
            pkgs_ninja.buildPackages.ninja  # 1.9.0
        ];

        shellHook = ''
            cowsay "Hello $FOO"
        '';

    FOO = "World";
}