Useful Libraries: Rake::Pipeline and Spade

Republished from Opperator blog

In doing research for whether Ember.js would be a good fit for Opperator, I took some notes about the process. I came across two useful libraries used in Ember.js that I hadn't heard of before. Rake::Pipeline helps package code assets together, and spade is a Javascript dependency manager. Here's a quick overview of what they do, and how you can use them in your project.

From the Rake::Pipeline docs:

Rake::Pipeline is a system for packaging assets for deployment to the web. It uses Rake under the hood for dependency management and updating output files based on input changes.

Think of Rake::Pipeline as a lighter and simpler Sprockets. It allows you to declaratively match filenames with regexps, and then run those matched files through custom filter classes. Here's an easy example of how to concatenate all files that end in .js, and then slap a license on the top

# Assetfile
input  "app/assets/javascripts"
output "public/javascripts"

class LicenseFilter < Filter
  LICENSE = File.read('LICENSE')

  def generate_output(inputs, output)
    output.write LICENSE
    output.write "\n"
    output.write inputs.map(&:read).join("\n")
  end
end

match "*.js" do
  filter Rake::Pipeline::ConcatFilter, "application.js"
  filter LicenseFilter
end

First you declare where you want your base input and output directory paths should be. The input directory will be where files will be matched up against. Next we define our own custom LicenseFilter, which is used to prefix input files with the contents of our LICENSE file. As you can guess from the arguments of the generate_output method, each element in the inputs array is an IO object that you can read from, and output is the destination of what you're writing.

Finally, we use the match block to specify that we want all files that end in .js to be run through the Rake::Pipeline::ConcatFilter and output to public/application.js. Then we run our LicenseFilter against the final file to prefix our license.

Spade is a package manager and file loader that reminds me of NPM. The goal of the library is to be able to package and require modules that can be run in a terminal and also in the browser. The browser part is obvious, but being able to run from the terminal is quite useful. For example, you can have an npm-like module named 'awesome-module', and from a terminal do:

spade preview  # opens in a browser with your module loaded
spade console  # start interactive repl
> require('awesome-module/main)

Alongside with spade-qunit, you can easily separate a library into a bunch of packages, test them separately, and view the results in a browser.