Node.js

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Install

  environment.systemPackages = with pkgs; [ nodejs ];

See nix search nodejs for additional versions like nodejs-12_x, etc.

Packaging

Package with yarn2nix

yarn2nix uses the yarn nodejs tool to create a file called yarn.lock, which in return can be used by yarn2nix to generate a usable yarn expression. This is what was needed to convert a small application server shackspace muellshack:

$ nix-shell -p yarn yarn2nix-moretea
$ yarn install
# creates yarn.lock
$ yarn2nix > yarn.nix
$ vim package.json
# add:    "bin": "app.js",
$ cat > default.nix <<EOF
with (import <nixpkgs> {});
rec {
  muellshack = yarn2nix-moretea.mkYarnPackage {
    name = "muellshack";
    src = ./.;
    packageJSON = ./package.json;
    yarnLock = ./yarn.lock;
    yarnNix = ./yarn.nix;
  };
}
EOF
$ sed -i '1i#!/usr/bin/env node' app.js
$ chmod +x app.js
$ nix-build

$ result/bin/muellshack

The complete diff can be found at the respective diff

FAQ

Using npm install -g fails

The following errors are to be expected.

npm ERR! Error: EACCES: permission denied, access '/nix/store/00000000000000000000000000000000-nodejs-6.14.3/lib/node_modules'
npm ERR!     at Error (native)
npm ERR!  { Error: EACCES: permission denied, access '/nix/store/00000000000000000000000000000000-nodejs-6.14.3/lib/node_modules'
npm ERR!     at Error (native)
npm ERR!   errno: -13,
npm ERR!   code: 'EACCES',
npm ERR!   syscall: 'access',
npm ERR!   path: '/nix/store/00000000000000000000000000000000-nodejs-6.14.3/lib/node_modules' }
npm ERR!
npm ERR! Please try running this command again as root/Administrator.

The store is read-only as it should be. Purity in Nix and NixOS makes it right not to allow installation using -g.

There are a couple solutions, none of them are strictly wrong. You can either configure npm so it installs globally to your home, or avoid using -g entirely. It is also possible, for node versions 8 and greater, to use npx.

Install to your home

This is done through configuring npm and amending your PATH.

 $ npm set prefix ~/.npm-global

Then, amend your PATH so it looks into $HOME/.npm-global.

Avoid using -g

This is a bit harder to implement, but creates a bit more strictness in your environment; it will be impossible accidentally make use of what would have been a globally installed package. The idea is to install it to either a temporary transitory folder or to the project folder, then run the locally installed instance of the package, the binaries are found under node_packages/.bin/.

 $ npm install uglify-es
[ ... ]

 $ ls -l node_modules/.bin/
total 0
lrwxrwxrwx 1 user users 25 Jul 17 15:34 uglifyjs -> ../uglify-es/bin/uglifyjs

 $ node_modules/.bin/uglifyjs --help
  Usage: uglifyjs [options] [files...]

direnv

If calling the executables with full path is too cumbersome, another elegant solution is to leverage direnv. Direnv is a shell-hook that can set directory-specific environment-variables. You basically add a file ".envrc" next to your "package.json" with the following content:

layout node

direnv then adds your "node_modules/.bin" to your path whenever you enter the directory. Please follow direnv's setup instructions on how to activate setup direnv in general.

Using npx

 $ nix-shell -p nodejs-8_x

 $ npx create-react-app --help
npx: installed 67 in 1.671s
  Usage: create-react-app <project-directory> [options]
[...]

Using npx with binaries

Some binaries obtained via npm will not work out of the box with NixOS, as they're dynamically linked to things that don't exist in NixOS (for good reason!)

They'll typically give some kind of ENOENT error. For example, npx cypress open might give an error like:

$ npx cypress open

Cypress failed to start.
This is usually caused by a missing library or dependency.
The error below should indicate which dependency is missing.
https://on.cypress.io/required-dependencies
If you are using Docker, we provide containers with all required dependencies installed.
----------
spawn /home/rkb/.cache/Cypress/4.10.0/Cypress/Cypress ENOENT

One quick workaround for this is to use steam-run to provide a placeholder FHS environment that *should* work; e.g. for the Cypress example above:

$ nix-env -iA nixos.steam-run

$ steam-run npx cypress open

-- Cypress opens successfully!

(Inspired by this discussion on discourse.nixos.org)

External Links

• node2nix