Skip to content
Switch branches/tags

Latest commit


Git stats


Failed to load latest commit information.
Latest commit message
Commit time

Stories in Ready

Gem to replace the Rails asset pipeline with a Grunt-based workflow, providing dependencies via Bower.

Half Pipe is a generator to get you up and running quickly with a Grunt setup for building client-side code in Rails apps. We believe that your asset workflow is yours and you should be able to configure it however you need to.

Who is this For?

This initial release assumes you have been using Grunt in non-Rails apps and would like to start using it in Rails as well. It uses Bower for dependency management, RequireJS for JavaScript modules and Sass for CSS. If you use alternatives to these tools, we'd love to hear from you.

Beta Version

NOTE This README refers to the beta version of Half Pipe. I highly recommend using the beta and following this README, but if you are on the 0.2 version please see the previous README.

We Want Feedback

Half Pipe is still in the early stages of development. The workflow has been extracted from our projects at D-I with inspiration from ember-app-kit. We are trying to build an extremely flexible and useful tool for front-end developers who work in Rails apps, while still adhering to good coding principles. If you want to use Half Pipe but feel hesitant for any reason, please feel free to open up an issue telling us why. As we progress towards a 1.0 release, we want to hear from you to make this tool the best it can be.

Getting Started

Half Pipe was presented in the talk "Asset Happiness" which you can watch on YouTube.


The Half Pipe gem is mostly a vehicle to bring a nice Grunt workflow into your Rails app. To set it up, add the following to your Gemfile:

gem 'half-pipe', :github => "d-i/half-pipe"

After you install the gem, you can run rails g half_pipe:install to setup the Grunt workflow. This will configure your app for node.js, copy over the Grunt setup, install node modules and run grunt build:public.

From here you can move your stylesheets from app/assets/stylesheets to app/styles (make sure you replace Sprockets directives with Sass or Less imports.

You can also move JavaScript files into app/scripts, but take care to make sure you wrap them in RequireJS modules (see for a quick overview of RequireJS) or else you won't be able to build.


Note: Currently LESS is only available in master, it will be in a future release of the gem. Make sure you update your Gemfile accordingly if you need it.

To setup your workflow to use LESS instead of SASS you can do so with the processor option:

rails g half_pipe:install --processor=less

Working on Assets

Front-end Developer Workflow

Run grunt server and Half Pipe will start up your Rails app with a preview server for your assets. Browse to http://localhost:3000 and use your app like normal. Grunt will watch assets and recompile automatically when you make changes. It will also restart your Rails app when you change files in config or lib, and any time you install new gems with Bundler.

Back-end Developer Workflow

If you don't need to work on assets, nothing really changes for you. If you've never used Grunt before, install it with npm install -g grunt-cli. Then run npm install to install dependencies and then grunt build:public to get the assets into your public folder. Once you've done that, you will only need to use Grunt when you need to get the latest changes to assets (this step will go away in the future, see #31).


There are built-in helpers for referencing most assets.

  • image_tag "avatar.png" will reference /assets/images/avatar.png
  • javascript_include_tag "main" will reference /assets/scripts/main.js
  • stylesheet_link_tag "main" will reference /assets/styles/main.css

Half Pipe also provides helpers for Sass:

  • image-url('avatar.png') compiles to url(/assets/images/avatar.png)
  • image-path('avatar.png') compiles to /assets/images/avatar.png

Usage of the app folder

Only put assets that need to be processed by Grunt in the app folder. For example, if you want to use Grunt to sprite your images then you can create an app/icons folder and output the sprite to public/assets/images. However, you should keep the rest of your images in your repository at public/assets/images. That way files that don't need to be processed will never get passed through Grunt, which makes it clear to everyone what is getting compiled and what isn't.

  • Including assets from Bower (JavaScript, Sass, Sass/CSS)



Include Bower dependencies by configuring RequireJS to find them. This is a manual process at the moment (see #40 for more info). When you install a new Bower component, open up config/build.js and add it to the paths config. Since grunt builds from a tmp directory, you will need to prefix the paths with '../../../../../bower_components' (see #55).


Half Pipe configures Sass automatically to include your configured bower components directory. For example, to import bourbon into your app add 'bourbon' to your bower.json as a dependency and then include it by adding:

@import "bourbon/app/assets/stylesheets/bourbon";

to app/styles/main.scss.

If you have a Bower component that includes standard CSS files instead of Sass templates, you can include those the same way, but prefixing the path with CSS:. For example, to include normalize.css add normalize.css as a dependency to your bower.json and then include it with:

@import "CSS:normalize-css/normalize";

Directory Structure

We believe that the directory structured imposed by the Rails asset pipeline was a step in the right direction, but did not go far enough in making client code a first-class part of your application. Given that, we have put assets at the same level as the rest of your Ruby code:

  • app/scripts - JavaScript files (currently all RequireJS modules)
  • app/styles - Sass templates


For a detailed history, see our releases page.


We're currently undergoing some pretty major changes in the Half Pipe workflow. See our milestones for what's coming in the near future.

Other Considerations

  • Precompilation of client-side templates
  • JavaScript module generator
  • Configurable asset directories
  • Better support for images
  • Support for additional module loaders (including ES6 modules)
  • Support for other frameworks and environments
  • Support for most popular AltJS languages
  • Splitting out app skeleton from node/grunt setup