view_cache_dependency API

A declarative API for specifying dependencies that affect template
cache digest computation. In your controller, specify any of said
dependencies:

  view_cache_dependency { "phone" if using_phone? }

When the block is evaluated, the resulting value is included in the
cache digest calculation, allowing you to generate different digests
for effectively the same template. (Mostly useful if you're mucking
with template load paths.)

2 files changed, 15 insertions, 8 deletions

diff --git a/actionpack/lib/action_view/digestor.rb b/actionpack/lib/action_view/digestor.rb
index f3f6b425a8..4507861dcc 100644
--- a/actionpack/lib/action_view/digestor.rb
+++ b/actionpack/lib/action_view/digestor.rb
@@ -24,16 +24,17 @@ module ActionView
     @@cache = ThreadSafe::Cache.new
 
     def self.digest(name, format, finder, options = {})
-      @@cache["#{name}.#{format}"] ||= begin
+      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).digest
+        klass.new(name, format, finder, options).digest
       end
     end
 
-    attr_reader :name, :format, :finder
+    attr_reader :name, :format, :finder, :options
 
-    def initialize(name, format, finder)
-      @name, @format, @finder = name, format, finder
+    def initialize(name, format, finder, options={})
+      @name, @format, @finder, @options = name, format, finder, options
     end
 
     def digest
@@ -81,9 +82,11 @@ module ActionView
       end
 
       def dependency_digest
-        dependencies.collect do |template_name|
+        template_digests = dependencies.collect do |template_name|
           Digestor.digest(template_name, format, finder, partial: true)
-        end.join("-")
+        end
+
+        (template_digests + injected_dependencies).join("-")
       end
 
       def render_dependencies
@@ -105,6 +108,10 @@ module ActionView
       def explicit_dependencies
         source.scan(EXPLICIT_DEPENDENCY).flatten.uniq
       end
+
+      def injected_dependencies
+        Array.wrap(options[:dependencies])
+      end
   end
 
   class PartialDigestor < Digestor # :nodoc:
diff --git a/actionpack/lib/action_view/helpers/cache_helper.rb b/actionpack/lib/action_view/helpers/cache_helper.rb
index 995aa10afb..8fc78ea7fb 100644
--- a/actionpack/lib/action_view/helpers/cache_helper.rb
+++ b/actionpack/lib/action_view/helpers/cache_helper.rb
@@ -167,7 +167,7 @@ module ActionView
         if @virtual_path
           [
             *Array(name.is_a?(Hash) ? controller.url_for(name).split("://").last : name),
-            Digestor.digest(@virtual_path, formats.last.to_sym, lookup_context)
+            Digestor.digest(@virtual_path, formats.last.to_sym, lookup_context, dependencies: view_cache_dependencies)
           ]
         else
           name