Follow up to rails-api#1454

PR rails-api#1454 was merged with some missing fixes. All these fixes are
addressed by this commit:
- Rename ActiveModel::Serializer::Adapter::JsonApi::Association to
ActiveModel::Serializer::Adapter::JsonApi::Relationship
- Move ActiveModel::Serializer::Adapter:: JsonApi::Relationship and
ActiveModel::Serializer::Adapter::JsonApi::ResourceIdentifier to
ActiveModel::Serializer::Adapter::JsonApi::ApiObjects module
- Add unit test for
ActiveModel::Serializer::Adapter::JsonApi::Relationship
- Add unit test for
ActiveModel::Serializer::Adapter::JsonApi::ResourceIdentifier

lib/active_model/serializer/adapter/json_api.rb

@@ -6,9 +6,8 @@ class JsonApi < Base
         autoload :PaginationLinks
         autoload :FragmentCache
         autoload :Link
-        autoload :Association
-        autoload :ResourceIdentifier
         autoload :Deserialization
+        require 'active_model/serializer/adapter/json_api/api_objects'
 
         # TODO: if we like this abstraction and other API objects to it,
         # then extract to its own file and require it.
@@ -99,7 +98,7 @@ def resource_objects_for(serializers)
         end
 
         def process_resource(serializer, primary)
-          resource_identifier = JsonApi::ResourceIdentifier.new(serializer).as_json
+          resource_identifier = ApiObjects::ResourceIdentifier.new(serializer).as_json
           return false unless @resource_identifiers.add?(resource_identifier)
 
           resource_object = resource_object_for(serializer)
@@ -135,7 +134,7 @@ def attributes_for(serializer, fields)
 
         def resource_object_for(serializer)
           resource_object = cache_check(serializer) do
-            resource_object = JsonApi::ResourceIdentifier.new(serializer).as_json
+            resource_object = ApiObjects::ResourceIdentifier.new(serializer).as_json
 
             requested_fields = fieldset && fieldset.fields_for(resource_object[:type])
             attributes = attributes_for(serializer, requested_fields)
@@ -156,12 +155,13 @@ def resource_object_for(serializer)
         def relationships_for(serializer, requested_associations)
           include_tree = IncludeTree.from_include_args(requested_associations)
           serializer.associations(include_tree).each_with_object({}) do |association, hash|
-            hash[association.key] = JsonApi::Association.new(serializer,
-                                                             association.serializer,
-                                                             association.options,
-                                                             association.links,
-                                                             association.meta)
-                                    .as_json
+            hash[association.key] = ApiObjects::Relationship.new(
+              serializer,
+              association.serializer,
+              association.options,
+              association.links,
+              association.meta
+            ).as_json
           end
         end
 

lib/active_model/serializer/adapter/json_api/api_objects.rb

@@ -0,0 +1,13 @@
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          extend ActiveSupport::Autoload
+          autoload :Relationship
+          autoload :ResourceIdentifier
+        end
+      end
+    end
+  end
+end

lib/active_model/serializer/adapter/json_api/api_objects/relationship.rb

@@ -0,0 +1,52 @@
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          class Relationship
+            def initialize(parent_serializer, serializer, options = {}, links = {}, meta = nil)
+              @object = parent_serializer.object
+              @scope = parent_serializer.scope
+
+              @options = options
+              @data = data_for(serializer, options)
+              @links = links.each_with_object({}) do |(key, value), hash|
+                hash[key] = Link.new(parent_serializer, value).as_json
+              end
+              @meta = meta.respond_to?(:call) ? parent_serializer.instance_eval(&meta) : meta
+            end
+
+            def as_json
+              hash = {}
+              hash[:data] = data if options[:include_data]
+              links = self.links
+              hash[:links] = links if links.any?
+              meta = self.meta
+              hash[:meta] = meta if meta
+
+              hash
+            end
+
+            protected
+
+            attr_reader :object, :scope, :data, :options, :links, :meta
+
+            private
+
+            def data_for(serializer, options)
+              if serializer.respond_to?(:each)
+                serializer.map { |s| ResourceIdentifier.new(s).as_json }
+              else
+                if options[:virtual_value]
+                  options[:virtual_value]
+                elsif serializer && serializer.object
+                  ResourceIdentifier.new(serializer).as_json
+                end
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/active_model/serializer/adapter/json_api/api_objects/resource_identifier.rb

@@ -0,0 +1,39 @@
+module ActiveModel
+  class Serializer
+    module Adapter
+      class JsonApi
+        module ApiObjects
+          class ResourceIdentifier
+            def initialize(serializer)
+              @id = id_for(serializer)
+              @type = type_for(serializer)
+            end
+
+            def as_json
+              { id: id, type: type }
+            end
+
+            protected
+
+            attr_reader :id, :type
+
+            private
+
+            def type_for(serializer)
+              return serializer._type if serializer._type
+              if ActiveModelSerializers.config.jsonapi_resource_type == :singular
+                serializer.object.class.model_name.singular
+              else
+                serializer.object.class.model_name.plural
+              end
+            end
+
+            def id_for(serializer)
+              serializer.read_attribute_for_serialization(:id).to_s
+            end
+          end
+        end
+      end
+    end
+  end
+end