1 files changed, 85 insertions, 0 deletions
diff --git a/actionview/lib/action_view/digestor.rb b/actionview/lib/action_view/digestor.rb
new file mode 100644
index 0000000000..9324a1ac50
--- /dev/null
+++ b/actionview/lib/action_view/digestor.rb
@@ -0,0 +1,85 @@
+require 'thread_safe'
+require 'action_view/dependency_tracker'
+
+module ActionView
+  class Digestor
+    cattr_reader(:cache)
+    @@cache = ThreadSafe::Cache.new
+
+    def self.digest(name, format, finder, options = {})
+      cache_key = [name, format] + Array.wrap(options[:dependencies])
+      @@cache[cache_key.join('.')] ||= begin
+        klass = options[:partial] || name.include?("/_") ? PartialDigestor : Digestor
+        klass.new(name, format, finder, options).digest
+      end
+    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("#{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
+      DependencyTracker.find_dependencies(name, template)
+    rescue ActionView::MissingTemplate
+      [] # File doesn't exist, so no dependencies
+    end
+
+    def nested_dependencies
+      dependencies.collect do |dependency|
+        dependencies = PartialDigestor.new(dependency, format, finder).nested_dependencies
+        dependencies.any? ? { dependency => dependencies } : dependency
+      end
+    end
+
+    private
+
+      def logger
+        ActionView::Base.logger
+      end
+
+      def logical_name
+        name.gsub(%r|/_|, "/")
+      end
+
+      def partial?
+        false
+      end
+
+      def template
+        @template ||= finder.find(logical_name, [], partial?, formats: [ format ])
+      end
+
+      def source
+        template.source
+      end
+
+      def dependency_digest
+        template_digests = dependencies.collect do |template_name|
+          Digestor.digest(template_name, format, finder, partial: true)
+        end
+
+        (template_digests + injected_dependencies).join("-")
+      end
+
+      def injected_dependencies
+        Array.wrap(options[:dependencies])
+      end
+  end
+
+  class PartialDigestor < Digestor # :nodoc:
+    def partial?
+      true
+    end
+  end
+end