Option to cache Pygments output for faster re-rendering.

Re-rendering ~200 posts with highlighting in many of them went from ~90 seconds to ~3 seconds with caching.

README.textile

@@ -141,6 +141,12 @@ use that to make your code blocks look pretty. To activate Pygments support
 during the conversion:
 
   $ jekyll --pygments
+
+Highlighting a blog post can take a second or two, and with a lot of posts,
+it adds up. You can tell Jekyll to cache pygments output in a directory for
+faster re-rendering:
+
+  $ jekyll --pygments-cache [PATH]
 
 h3. Markdown Processor
 

bin/jekyll

@@ -43,6 +43,10 @@ opts = OptionParser.new do |opts|
   opts.on("--pygments", "Use pygments to highlight code") do
     options['pygments'] = true
   end
+
+  opts.on("--pygments-cache", "Path to cache pygments output in, for faster re-rendering") do |path|
+    options['pygments_cache'] = path
+  end
 
   opts.on("--rdiscount", "Use rdiscount gem for Markdown") do
     options['markdown'] = 'rdiscount'

lib/jekyll/site.rb

@@ -2,7 +2,7 @@ module Jekyll
 
   class Site
     attr_accessor :config, :layouts, :posts, :collated_posts, :categories
-    attr_accessor :source, :dest, :lsi, :pygments, :permalink_style, :permalink_date,
+    attr_accessor :source, :dest, :lsi, :pygments, :pygments_cache, :permalink_style, :permalink_date,
                   :sass, :post_defaults
 
     # Initialize the site
@@ -16,6 +16,7 @@ def initialize(config)
       self.dest            = config['destination']
       self.lsi             = config['lsi']
       self.pygments        = config['pygments']
+      self.pygments_cache  = config['pygments_cache']
       self.permalink_style = config['permalink'].to_sym
       self.permalink_date  = config['permalink_date'] && config['permalink_date'].sub(%r{\A/?(.*)/?\Z}, '/\1/')
       self.post_defaults   = config['post_defaults'] || {}
@@ -55,6 +56,12 @@ def setup
           puts 'You must have the haml gem installed first'
         end
       end
+
+      if self.pygments_cache
+        require 'fileutils'
+        FileUtils.mkdir_p(pygments_cache)
+        require 'digest/md5'
+      end
 
       # Set the Markdown interpreter (and Maruku self.config, if necessary)
       case self.config['markdown']

lib/jekyll/tags/highlight.rb

@@ -30,12 +30,24 @@ def render(context)
     end
 
     def render_pygments(context, code)
+      if cache_dir = context.registers[:site].pygments_cache
+        path = File.join(cache_dir, "#{@lang}-#{Digest::MD5.hexdigest(code)}.html")
+        if File.exist?(path)
+          highlighted_code = File.read(path)
+        else
+          highlighted_code = Albino.new(code, @lang).to_s(@options)
+          File.open(path, 'w') {|f| f.print(highlighted_code) }
+        end
+      else
+        highlighted_code = Albino.new(code, @lang).to_s(@options)
+      end
+
       if context["content_type"] == :markdown
-        return "\n" + Albino.new(code, @lang).to_s(@options) + "\n"
+        return "\n" + highlighted_code + "\n"
       elsif context["content_type"] == :textile
-        return "<notextile>" + Albino.new(code, @lang).to_s(@options) + "</notextile>"
+        return "<notextile>" + highlighted_code + "</notextile>"
       else
-        return Albino.new(code, @lang).to_s(@options)
+        return highlighted_code
       end
     end