Merge pull request #8818 from jamis/master

view_cache_dependency API

actionpack/CHANGELOG.md

 ## Rails 4.0.0 (unreleased) ##
 
+*   Added view_cache_dependency API for declaring dependencies that affect
+    cache digest computation.
+
+    *Jamis Buck*
+
 *   `image_submit_tag` will set `alt` attribute from image source if not
     specified.
 

actionpack/lib/action_controller/caching.rb

@@ -70,12 +70,30 @@ def self.page_cache_extension
 
       config_accessor :perform_caching
       self.perform_caching = true if perform_caching.nil?
+
+      class_attribute :_view_cache_dependencies
+      self._view_cache_dependencies = []
+      helper_method :view_cache_dependencies if respond_to?(:helper_method)
+    end
+
+    module ClassMethods
+      def view_cache_dependency(&dependency)
+        self._view_cache_dependencies += [dependency]
+      end
+
+      def view_cache_dependencies
+        _view_cache_dependencies.map { |dep| instance_exec &dep }.compact
+      end
     end
 
     def caching_allowed?
       request.get? && response.status == 200
     end
 
+    def view_cache_dependencies
+      self.class.view_cache_dependencies
+    end
+
     protected
       # Convenience accessor.
       def cache(key, options = {}, &block)

actionpack/lib/action_view/digestor.rb

@@ -24,16 +24,17 @@ class Digestor
     @@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 @@ def source
       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 @@ def render_dependencies
       def explicit_dependencies
         source.scan(EXPLICIT_DEPENDENCY).flatten.uniq
       end
+
+      def injected_dependencies
+        Array.wrap(options[:dependencies])
+      end
   end
 
   class PartialDigestor < Digestor # :nodoc:

actionpack/lib/action_view/helpers/cache_helper.rb

@@ -167,7 +167,7 @@ def fragment_name_with_digest(name) #:nodoc:
         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

actionpack/test/controller/caching_test.rb

@@ -296,6 +296,24 @@ def test_safe_buffer
   end
 end
 
+class ViewCacheDependencyTest < ActionController::TestCase
+  class NoDependenciesController < ActionController::Base
+  end
+
+  class HasDependenciesController < ActionController::Base
+    view_cache_dependency { "trombone" }
+    view_cache_dependency { "flute" }
+  end
+
+  def test_view_cache_dependencies_are_empty_by_default
+    assert NoDependenciesController.view_cache_dependencies.empty?
+  end
+
+  def test_view_cache_dependencies_are_listed_in_declaration_order
+    assert_equal %w(trombone flute), HasDependenciesController.view_cache_dependencies
+  end
+end
+
 class DeprecatedPageCacheExtensionTest < ActiveSupport::TestCase
   def test_page_cache_extension_binds_default_static_extension
     deprecation_behavior = ActiveSupport::Deprecation.behavior

actionpack/test/template/digestor_test.rb

@@ -138,6 +138,20 @@ def test_old_style_hash_in_render_invocation
     end
   end
 
+  def test_dependencies_via_options_results_in_different_digest
+    digest_plain        = digest("comments/_comment")
+    digest_fridge       = digest("comments/_comment", dependencies: ["fridge"])
+    digest_phone        = digest("comments/_comment", dependencies: ["phone"])
+    digest_fridge_phone = digest("comments/_comment", dependencies: ["fridge", "phone"])
+
+    assert_not_equal digest_plain, digest_fridge
+    assert_not_equal digest_plain, digest_phone
+    assert_not_equal digest_plain, digest_fridge_phone
+    assert_not_equal digest_fridge, digest_phone
+    assert_not_equal digest_fridge, digest_fridge_phone
+    assert_not_equal digest_phone, digest_fridge_phone
+  end
+
   private
     def assert_logged(message)
       old_logger = ActionView::Base.logger
@@ -164,8 +178,8 @@ def assert_digest_difference(template_name)
       ActionView::Digestor.cache.clear
     end
 
-    def digest(template_name)
-      ActionView::Digestor.digest(template_name, :html, FixtureFinder.new)
+    def digest(template_name, options={})
+      ActionView::Digestor.digest(template_name, :html, FixtureFinder.new, options)
     end
 
     def change_template(template_name)