Rack::Highlighter

Rack Middleware that provides syntax highlighting of code blocks, using the CodeRay, Pygments, Rouge or Ultraviolet gems.

Installation

Add this line to your application's Gemfile:

gem 'rack-highlighter'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rack-highlighter

Usage

Adding highlighting to a Rails application

require 'rack/highlighter'
require 'pygments'

class Application < Rails::Application
  config.middleware.use Rack::Highlighter, :pygments
end

Adding highlighting to a Sinatra application

require 'sinatra'
require 'rack/highlighter'
require 'pygments'

use Rack::Highlighter, :pygments

get('/') do
  '<pre><code class="ruby">puts "Hello world!"</code></pre>'
end

Adding highlighting to a Rackup application

require 'rack'
require 'rack/highlighter'
require 'pygments'

use Rack::Highlighter, :pygments

run lambda { |env|
  [200, {'Content-Type' => 'text/html'}, ['<pre><code class="ruby">puts "Hello world!"</code></pre>']]
}

Highlighters

You can choose which highlighter to use. Just require the right gem, and specify it when invoking the middleware.

CodeRay

require 'rack/highlighter'
require 'coderay'

use Rack::Highlighter, :coderay

Pygments

require 'rack/highlighter'
require 'pygments'

use Rack::Highlighter, :pygments

Rouge

require 'rack/highlighter'
require 'rouge'

use Rack::Highlighter, :rouge

Ultraviolet

require 'rack/highlighter'
require 'uv'

use Rack::Highlighter, :ultraviolet

Configuration

Default

With the default options, Rack::Highlighter would recognize code blocks like the following:

<pre>
  <code class="ruby">puts "Hello world!"</code>
</pre>

Elements

If your code is wrapped in other tags, for example:

<pre class="ruby">puts "Hello world!"</pre>

You can specify them in the elements option:

use Rack::Highlighter, :pygments, { elements: ['pre'] }

Attribute

If your block doesn't use the class attribute to declare the language of the code, for example:

<pre>
  <code data-lang="ruby">puts "Hello world!"</code>
</pre>

You can specify it in the attribute option:

use Rack::Highlighter, :pygments, { attribute: 'data-lang' }

Pattern

If your block uses a certain pattern to declare the language of the code, for example:

<pre>
  <code class="language-ruby">puts "Hello world!"</code>
</pre>

You can specify a regular expression to match it in the pattern option:

use Rack::Highlighter, :pygments, { pattern: /language-(?<lang>\w+)/ }

The regular expression must have a capture group named lang for this to work.

Additional parameters

You can pass additional parameters to the highlighter via the misc option:

use Rack::Highlighter, :pygments, { misc: {linenos: 'inline'} }

Contributors

Daniel Perez Alvarez (unindented@gmail.com)