1 files changed, 104 insertions, 0 deletions
diff --git a/actionpack/lib/action_view/digestor.rb b/actionpack/lib/action_view/digestor.rb
new file mode 100644
index 0000000000..cfa864cdd4
--- /dev/null
+++ b/actionpack/lib/action_view/digestor.rb
@@ -0,0 +1,104 @@
+require 'active_support/core_ext'
+require 'logger'
+
+module ActionView
+  class Digestor
+    EXPLICIT_DEPENDENCY = /# Template Dependency: ([^ ]+)/
+
+    # Matches:
+    #   render partial: "comments/comment", collection: commentable.comments
+    #   render "comments/comments"
+    #   render 'comments/comments'
+    #   render('comments/comments')
+    #
+    #   render(@topic)         => render("topics/topic")
+    #   render(topics)         => render("topics/topic")
+    #   render(message.topics) => render("topics/topic")
+    RENDER_DEPENDENCY = /
+      render\s?                # render, followed by an optional space
+      \(?                      # start a optional parenthesis for the render call
+      (partial:)?\s?           # naming the partial, used with collection -- 1st capture
+      ([@a-z"'][@a-z_\/\."']+) # the template name itself -- 2nd capture
+    /x
+
+    cattr_accessor(:cache)  { Hash.new }
+    cattr_accessor(:logger, instance_reader: true) { ActionView::Base.logger }
+
+    def self.digest(name, format, finder, options = {})
+      cache["#{name}.#{format}"] ||= new(name, format, finder, options).digest
+    end
+
+    attr_reader :name, :format, :finder, :options
+
+    def initialize(name, format, finder, options = {})
+      @name, @format, @finder, @options = name, format, finder, options
+    end
+
+    def digest
+      Digest::MD5.hexdigest("#{name}.#{format}-#{source}-#{dependency_digest}").tap do |digest|
+        logger.try :info, "Cache digest for #{name}.#{format}: #{digest}"
+      end
+    rescue ActionView::MissingTemplate
+      logger.try :error, "Couldn't find template for digesting: #{name}.#{format}"
+      ''
+    end
+
+    def dependencies
+      render_dependencies + explicit_dependencies
+    rescue ActionView::MissingTemplate
+      [] # File doesn't exist, so no dependencies
+    end
+
+    def nested_dependencies
+      dependencies.collect do |dependency|
+        dependencies = Digestor.new(dependency, format, finder, partial: true).nested_dependencies
+        dependencies.any? ? { dependency => dependencies } : dependency
+      end
+    end
+
+
+    private
+      def logical_name
+        name.gsub(%r|/_|, "/")
+      end
+      
+      def directory
+        name.split("/").first
+      end
+
+      def partial?
+        options[:partial] || name.include?("/_")
+      end
+
+      def source
+        @source ||= finder.find(logical_name, [], partial?, formats: [ format ]).source
+      end
+
+
+      def dependency_digest
+        dependencies.collect do |template_name|
+          Digestor.digest(template_name, format, finder, partial: true)
+        end.join("-")
+      end
+
+      def render_dependencies
+        source.scan(RENDER_DEPENDENCY).
+          collect(&:second).uniq.
+
+          # render(@topic)         => render("topics/topic")
+          # render(topics)         => render("topics/topic")
+          # render(message.topics) => render("topics/topic")
+          collect { |name| name.sub(/\A@?([a-z]+\.)*([a-z_]+)\z/) { "#{$2.pluralize}/#{$2.singularize}" } }.
+
+          # render("headline") => render("message/headline")
+          collect { |name| name.include?("/") ? name : "#{directory}/#{name}" }.
+          
+          # replace quotes from string renders
+          collect { |name| name.gsub(/["']/, "") }
+      end
+
+      def explicit_dependencies
+        source.scan(EXPLICIT_DEPENDENCY).flatten.uniq
+      end
+  end
+end
+\ No newline at end of file