Refactor: introduce lazy association

lib/active_model/serializer/association.rb

@@ -1,3 +1,5 @@
+require 'active_model/serializer/lazy_association'
+
 module ActiveModel
   class Serializer
     # This class holds all information about serializer's association.
@@ -10,14 +12,22 @@ module ActiveModel
     #  Association.new(:comments, { serializer: CommentSummarySerializer })
     #
     class Association < Field
+      attr_reader :lazy_association
+      delegate :include_data?, :virtual_value, to: :lazy_association
+
+      def initialize(*)
+        super
+        @lazy_association = LazyAssociation.new(name, options, block)
+      end
+
       # @return [Symbol]
       def key
         options.fetch(:key, name)
       end
 
-      # @return [ActiveModel::Serializer, nil]
-      def serializer
-        options[:serializer]
+      # @return [True,False]
+      def key?
+        options.key?(:key)
       end
 
       # @return [Hash]
@@ -30,21 +40,30 @@ module ActiveModel
         options[:meta]
       end
 
+      def polymorphic?
+        true == options[:polymorphic]
+      end
+
       # @api private
       def serializable_hash(adapter_options, adapter_instance)
-        return options[:virtual_value] if options[:virtual_value]
-        object = serializer && serializer.object
-        return unless object
+        association_serializer = lazy_association.serializer
+        return virtual_value if virtual_value
+        association_object = association_serializer && association_serializer.object
+        return unless association_object
 
-        serialization = serializer.serializable_hash(adapter_options, {}, adapter_instance)
+        serialization = association_serializer.serializable_hash(adapter_options, {}, adapter_instance)
 
-        if options[:polymorphic] && serialization
-          polymorphic_type = object.class.name.underscore
+        if polymorphic? && serialization
+          polymorphic_type = association_object.class.name.underscore
           serialization = { type: polymorphic_type, polymorphic_type.to_sym => serialization }
         end
 
         serialization
       end
+
+      private
+
+      delegate :reflection, to: :lazy_association
     end
   end
 end

lib/active_model/serializer/concerns/caching.rb

@@ -193,12 +193,13 @@ module ActiveModel
             cache_keys << object_cache_key(serializer, adapter_instance)
 
             serializer.associations(include_directive).each do |association|
-              if association.serializer.respond_to?(:each)
-                association.serializer.each do |sub_serializer|
+              association_serializer = association.lazy_association.serializer
+              if association_serializer.respond_to?(:each)
+                association_serializer.each do |sub_serializer|
                   cache_keys << object_cache_key(sub_serializer, adapter_instance)
                 end
               else
-                cache_keys << object_cache_key(association.serializer, adapter_instance)
+                cache_keys << object_cache_key(association_serializer, adapter_instance)
               end
             end
           end

lib/active_model/serializer/lazy_association.rb

@@ -0,0 +1,22 @@
+module ActiveModel
+  class Serializer
+    class LazyAssociation < Field
+
+      def serializer
+        options[:serializer]
+      end
+
+      def include_data?
+        options[:include_data]
+      end
+
+      def virtual_value
+        options[:virtual_value]
+      end
+
+      def reflection
+        options[:reflection]
+      end
+    end
+  end
+end

lib/active_model/serializer/reflection.rb

@@ -170,7 +170,11 @@ module ActiveModel
         end
 
         association_block = nil
-        Association.new(name, reflection_options, association_block)
+        reflection_options[:reflection] = self
+        reflection_options[:parent_serializer] = parent_serializer
+        reflection_options[:parent_serializer_options] = parent_serializer_options
+        reflection_options[:include_slice] = include_slice
+        Association.new(name, reflection_options, block)
       end
 
       protected

lib/active_model_serializers/adapter/json_api.rb

@@ -257,7 +257,7 @@ module ActiveModelSerializers
 
       def process_relationships(serializer, include_slice)
         serializer.associations(include_slice).each do |association|
-          process_relationship(association.serializer, include_slice[association.key])
+          process_relationship(association.lazy_association.serializer, include_slice[association.key])
         end
       end
 

lib/active_model_serializers/adapter/json_api/relationship.rb

@@ -15,9 +15,7 @@ module ActiveModelSerializers
         def as_json
           hash = {}
 
-          if association.options[:include_data]
-            hash[:data] = data_for(association)
-          end
+          hash[:data] = data_for(association) if association.include_data?
 
           links = links_for(association)
           hash[:links] = links if links.any?
@@ -36,10 +34,10 @@ module ActiveModelSerializers
         private
 
         def data_for(association)
-          serializer = association.serializer
+          serializer = association.lazy_association.serializer
           if serializer.respond_to?(:each)
             serializer.map { |s| ResourceIdentifier.new(s, serializable_resource_options).as_json }
-          elsif (virtual_value = association.options[:virtual_value])
+          elsif (virtual_value = association.virtual_value)
             virtual_value
           elsif serializer && serializer.object
             ResourceIdentifier.new(serializer, serializable_resource_options).as_json