Remove unnecessary Serializer#cached_fields; Extracted cached_attributes

lib/active_model/serializer/caching.rb

@@ -1,3 +1,5 @@
+# TODO(BF): refactor file to be smaller
+# rubocop:disable Metrics/ModuleLength
 module ActiveModel
   class Serializer
     UndefinedCacheKey = Class.new(StandardError)
@@ -206,12 +208,18 @@ def object_cache_key(serializer, adapter_instance)
         end
       end
 
-      # Get attributes from @cached_attributes
-      # @return [Hash] cached attributes
-      # def cached_attributes(fields, adapter_instance)
-      def cached_fields(fields, adapter_instance)
-        cache_check(adapter_instance) do
-          attributes(fields)
+      def cached_attributes(fields, cached_attributes, adapter_instance)
+        if self.class.cache_enabled?
+          key = cache_key(adapter_instance)
+          cached_attributes.fetch(key) do
+            cache_check(adapter_instance) do
+              attributes(fields)
+            end
+          end
+        else
+          cache_check(adapter_instance) do
+            attributes(fields)
+          end
         end
       end
 
@@ -331,3 +339,4 @@ def object_cache_key
     end
   end
 end
+# rubocop:enable Metrics/ModuleLength

lib/active_model_serializers/adapter/attributes.rb

@@ -32,7 +32,8 @@ def serializable_hash_for_collection(options)
       end
 
       def serializable_hash_for_single_resource(options)
-        resource = resource_object_for(options)
+        cached_attributes = instance_options[:cached_attributes] || {}
+        resource = serializer.cached_attributes(options[:fields], cached_attributes, self)
         relationships = resource_relationships(options)
         resource.merge(relationships)
       end
@@ -60,18 +61,6 @@ def relationship_value_for(association, options)
 
         relationship_value
       end
-
-      def resource_object_for(options)
-        if serializer.class.cache_enabled?
-          cached_attributes = instance_options[:cached_attributes] || {}
-          key = serializer.cache_key(self)
-          cached_attributes.fetch(key) do
-            serializer.cached_fields(options[:fields], self)
-          end
-        else
-          serializer.cached_fields(options[:fields], self)
-        end
-      end
     end
   end
 end