Add explicit opt-out for fragment cache digesting

This add support for sending an explicit opt-out of the "Russian-doll"
cache digest feature on a case-by-case basis. This is useful when cache-
expiration needs to be performed manually and it would be otherwise
difficult to know the exact name of a digested cache key.

More information: https://github.com/rails/cache_digests/pull/16

1 files changed, 23 insertions, 1 deletions

diff --git a/actionpack/lib/action_view/helpers/cache_helper.rb b/actionpack/lib/action_view/helpers/cache_helper.rb
index ddac87a37d..fbaba63997 100644
--- a/actionpack/lib/action_view/helpers/cache_helper.rb
+++ b/actionpack/lib/action_view/helpers/cache_helper.rb
@@ -52,6 +52,13 @@ module ActionView
       # Additionally, the digestor will automatically look through your template file for
       # explicit and implicit dependencies, and include those as part of the digest.
       #
+      # The digestor can be bypassed by passing skip_digest: true as an option to the cache call:
+      #
+      #   <% cache project, skip_digest: true do %>
+      #     <b>All the topics on this project</b>
+      #     <%= render project.topics %>
+      #   <% end %>
+      #
       # ==== Implicit dependencies
       #
       # Most template dependencies can be derived from calls to render in the template itself.
@@ -105,7 +112,7 @@ module ActionView
       # Now all you'll have to do is change that timestamp when the helper method changes.
       def cache(name = {}, options = nil, &block)
         if controller.perform_caching
-          safe_concat(fragment_for(fragment_name_with_digest(name), options, &block))
+          safe_concat(fragment_for(cache_fragment_name(name, options), options, &block))
         else
           yield
         end
@@ -113,6 +120,21 @@ module ActionView
         nil
       end
 
+      # This helper returns the name of a cache key for a given fragment cache
+      # call. By supplying skip_digest: true to cache, the digestion of cache
+      # fragments can be manually bypassed. This is useful when cache fragments
+      # cannot be manually expired unless you know the exact key which is the
+      # case when using memcached.
+      def cache_fragment_name(name = {}, options = nil)
+        skip_digest = options && options.delete(:skip_digest)
+
+        if skip_digest
+          name
+        else
+          fragment_name_with_digest(name)
+        end
+      end
+
       def fragment_name_with_digest(name) #:nodoc:
         if @virtual_path
           [