This is the gist of the cssbundling gem. It’s just a rake task that is added to the
namespace :css do
task :build do
system "yarn install && yarn build:css"
And it expects
yarn build:css to put your compiled stylesheet in
/app/assets/builds/application.css, and if you’re using Sprockets, the
builds directory needs to be added to your assets
All the heavy lifting is done by what you’ve configured
build:css to do. And the jsbundling-rails gem is nearly identical, except it calls
build in your
The “magic” happens with Sprockets knowing about these files through the manifest configuration file.
In Development Mode
There are some drawbacks to this setup. Changes you make to your source files are not picked up automatically in development in your
rails server process like the traditional Rails assets pipeline. You will need an external process watching your source files for changes and putting the compiled changes in the
Both bundling gems setup a
Procfile.dev and a
bin/dev executable that will delegate running
rails server and your building script(s) in watch mode concurrently to the foreman gem.
At my work, we don’t use yarn, so we’ve actually recreated these gems as a simple rake file in our project that calls
npm instead. Normally I would be against recreating the functionality of a gem and taking on the maintenance burden, but these gems do so little in practice.
These gems are a breath of fresh air compared to the now retired Webpacker gem. They stay true to the convention over configuration mantra of Ruby on Rails and will not add a brittle component to your asset pipeline that will cause you worry as Rails or your preferred asset libraries get updated.