Adding custom NPM program to home-manager

home-manager is a tool that allows you to declaritively define reproducible home environments (think dotfiles on steroids), including what packages are available for a user.

Packages can be installed from nixpkgs by adding the following to your home.nix

home.packages = [
  htop
  shell
  ...
];

Packages available on NPM can be installed using nodePackages like

home.packages = [
  nodePackages.webpack-cli
];

However, only a select number of packages are made available in nixpkgs. Short of creating a pull-request requesting the new package, we can follow these steps:

Create a node folder

Navigate to your home.nix installation and create a node folder

cd ~/.config/nixpkgs 
mkdir -p node
touch node/node-packages.json

Create a node-packages.json

The node-packages.json file should define all packages you want to install from npm.

Here's an example I use

[
  "aws-azure-login"
]

Generate relevant nix files with node2nix

Using nix-shell gives us a convenient one-liner (Note: I could make this a nix-shell script called update.sh or similar in the future. This works for me now)

cd node
nix-shell -p nodePackages.node2nix --command "node2nix -i ./node-packages.json -o node-packages.nix"

Import generated default.nix on your home.nix

In your home.nix you can now reference the packages by importing the node/default.nix file

let
  extraNodePackages = import ./node/default.nix {};
in
  home.packages = [
    ...
    extraNodePackages.aws-azure-login
  ];