blog/_plugins/kramdown-with-pygments/kramdown_pygments.rb

# We define the an additional option for the kramdown parser to look for
module Kramdown
  module Options
      define(:kramdown_default_lang, Symbol, nil, <<EOF)
Sets the default language for highlighting code blocks

If no language is set for a code block, the default language is used
instead. The value has to be one of the languages supported by pygments
or nil if no default language should be used.

Default: nil
Used by: PygmentsHtml converter
EOF
  end
end

# This class is a plugin for kramdown, to make it use pygments instead of coderay
# It has nothing to do with Jekyll, it is simply used by the custom converter below
module Kramdown
  module Converter
    class PygmentsHtml < Html

      begin
        require 'pygments'
      rescue LoadError
        STDERR.puts 'You are missing a library required for syntax highlighting. Please run:'
        STDERR.puts '  $ [sudo] gem install pygments'
        raise FatalException.new("Missing dependency: Pygments")
      end

      def extract_code_language_with_fix!(attr)
        lang = extract_code_language!(attr) || @options[:kramdown_default_lang]
        lang = "bash" if lang == "shell"
        lang
      end

      def convert_codeblock(el, indent)
        attr = el.attr.dup
        lang = extract_code_language_with_fix!(attr)
        code = pygmentize(el.value, lang)
        code_attr = {}
        code_attr['class'] = "language-#{lang}" if lang
        "#{' '*indent}<div class=\"highlight\"><pre#{html_attributes(attr)}><code#{html_attributes(code_attr)}>#{code}</code></pre></div>\n"
      end

      def convert_codespan(el, indent)
        attr = el.attr.dup
        lang = extract_code_language_with_fix!(attr)
        code = pygmentize(el.value, lang)
        if lang
          attr['class'] = "highlight"
          if attr.has_key?('class')
            attr['class'] += " language-#{lang}"
          else
            attr['class'] = "language-#{lang}"
          end
        end
        "<code#{html_attributes(attr)}>#{code}</code>"
      end

      def pygmentize(code, lang)
        if lang
          Pygments.highlight(code,
            :lexer => lang,
            :options => { :startinline => true, :encoding => 'utf-8', :nowrap => true })
        else
          escape_html(code)
        end
      end
    end
  end
end

# This class is the actual custom Jekyll converter.
class Jekyll::Converters::Markdown::KramdownPygments

  def initialize(config)
    require 'kramdown'
    @config = config
  rescue LoadError
    STDERR.puts 'You are missing a library required for Markdown. Please run:'
    STDERR.puts '  $ [sudo] gem install kramdown'
    raise FatalException.new("Missing dependency: kramdown")
  end

  def convert(content)
    Kramdown::Document.new(content, @config['kramdown']).to_pygments_html
  end
end