Using Nix to run a Rails project

Environment.md

Create new Rails project $PROJECT_NAME:

$ nix-shell -p "ruby_3_0.withPackages (ps: with ps; [ rails ])" -p bundix -p sqlite \
    --run "rails new $PROJECT_NAME --skip-bundle --webpacker react && \
       cd $PROJECT_NAME && \
       bundle config set force_ruby_platform true && \
       bundle lock && \
       bundix --ruby=ruby_3_0"

Create shell.nix, replace $PROJECT_NAME with your project name:

{ pkgs ? import <nixpkgs> {} }:

with pkgs;
let
  env = bundlerEnv {
    name = "$PROJECT_NAME-bundle";
    gemdir = ./.;
    ruby = ruby_3_0;
  };

in mkShell {
  buildInputs = [
    env
    env.wrappedRuby

    # Additional utilities
    sqlite
    nodejs-16_x
    yarn
  ];
}

Post install:

$ rails webpacker:install
$ rails db:migrate

Update.md

To update Rails versions (or any other gem versions):

1. Make changes in Gemfile

2. Remove lockfile: rm Gemfile.lock

3. Run: nix-shell -p bundix --run "bundle lock && bundix --ruby=ruby_3_0"

   This does 2 things:

   1. Updates the lockfile
   2. Creates the updated gemset.nix