Serializers now inherit attributes

lib/active_model/serializer.rb

@@ -22,9 +22,9 @@ class << self
     end
 
     def self.inherited(base)
-      base._attributes = []
-      base._attributes_keys = {}
-      base._associations = {}
+      base._attributes = self._attributes.try(:dup)  || []
+      base._attributes_keys = self._attributes_keys.try(:dup) || {}
+      base._associations = self._associations.try(:dup) || {}
       base._urls = []
     end
 

test/serializers/associations_test.rb

@@ -101,6 +101,27 @@ def test_belongs_to_with_custom_method
 
         assert blog_is_present
       end
+
+      def test_associations_inheritance
+        inherited_klass = Class.new(PostSerializer)
+
+        assert_equal(PostSerializer._associations, inherited_klass._associations)
+      end
+
+      def test_associations_inheritance_with_new_association
+        inherited_klass = Class.new(PostSerializer) do
+          has_many :top_comments, serializer: CommentSerializer
+        end
+        expected_associations = PostSerializer._associations.merge(
+          top_comments: {
+            type: :has_many,
+            association_options: {
+              serializer: CommentSerializer
+            }
+          }
+        )
+        assert_equal(inherited_klass._associations, expected_associations)
+      end
     end
   end
 end

test/serializers/attribute_test.rb

@@ -17,7 +17,13 @@ def test_json_serializable_hash
         adapter = ActiveModel::Serializer::Adapter::Json.new(@blog_serializer)
         assert_equal({:id=>1, :title=>"AMS Hints"}, adapter.serializable_hash)
       end
+
+      def test_attribute_inheritance_with_key
+        inherited_klass = Class.new(AlternateBlogSerializer)
+        blog_serializer = inherited_klass.new(@blog)
+        adapter = ActiveModel::Serializer::Adapter::Json.new(blog_serializer)
+        assert_equal({:id=>1, :title=>"AMS Hints"}, adapter.serializable_hash)
+      end
     end
   end
 end
-

test/serializers/attributes_test.rb

@@ -6,6 +6,11 @@ class AttributesTest < Minitest::Test
       def setup
         @profile = Profile.new({ name: 'Name 1', description: 'Description 1', comments: 'Comments 1' })
         @profile_serializer = ProfileSerializer.new(@profile)
+        @comment = Comment.new(id: 1, body: "ZOMG!!", date: "2015")
+        @serializer_klass = Class.new(CommentSerializer)
+        @serializer_klass_with_new_attributes = Class.new(CommentSerializer) do
+          attributes :date, :likes
+        end
       end
 
       def test_attributes_definition
@@ -23,6 +28,27 @@ def test_required_fields
                      @profile_serializer.attributes(fields: [:name, :description], required_fields: [:name]))
 
       end
+
+      def test_attributes_inheritance_definition
+        assert_equal([:id, :body], @serializer_klass._attributes)
+      end
+
+      def test_attributes_inheritance
+        serializer = @serializer_klass.new(@comment)
+        assert_equal({id: 1, body: "ZOMG!!"},
+                     serializer.attributes)
+      end
+
+      def test_attribute_inheritance_with_new_attribute_definition
+        assert_equal([:id, :body, :date, :likes], @serializer_klass_with_new_attributes._attributes)
+        assert_equal([:id, :body], CommentSerializer._attributes)
+      end
+
+      def test_attribute_inheritance_with_new_attribute
+        serializer = @serializer_klass_with_new_attributes.new(@comment)
+        assert_equal({id: 1, body: "ZOMG!!", date: "2015", likes: nil},
+                     serializer.attributes)
+      end
     end
   end
 end