Jekyll plugin to import code blocks from the filesystem for syntax highlighting

code_blocks.rb

require 'pathname'

module Jekyll

  class CodeBlockTag < Liquid::Tag
    def initialize(tag_name, file, tokens)
      super
      @file = file.strip
    end

    def render(context)
      code_dir = (context.registers[:site].config['code_dir'] || 'downloads/code')
      code_path = (Pathname.new(context.registers[:site].source) + code_dir).expand_path
      file = code_path + @file

      if File.symlink?(code_path)
        return "Code directory '#{code_path}' cannot be a symlink"
      end

      unless file.file?
        return "File #{file} could not be found"
      end

      Dir.chdir(code_path) do
        source = file.read
        file_type = file.extname
        url = "#{context.registers[:site].config['url']}/#{code_dir}/#{file.basename}"
        source = "<figure>{% highlight #{file_type} %}\n" + source + "\n{% endhighlight %}"
        source += "<figcaption><span>#{file.basename}</span><a href='#{url}'>Download</a></figcaption></figure>"
        partial = Liquid::Template.parse(source)
        context.stack do
          partial.render(context)
        end
      end
    end
  end

end

Liquid::Template.register_tag('codeblock', Jekyll::CodeBlockTag)