Pass fields down from constructor

Author: vasilakisfil

lib/active_model_serializers/adapter/attributes.rb

@@ -3,6 +3,7 @@ module Adapter
     class Attributes < Base
       def serializable_hash(options = nil)
         options = serialization_options(options)
+        options[:fields] ||= instance_options[:fields]
         serializer.serializable_hash(instance_options, options, self)
       end
     end

test/adapter/json/collection_test.rb

@@ -84,6 +84,20 @@ def test_include_option
 
           assert_equal(expected, actual)
         end
+
+        def test_fields_with_no_associations_include_option
+          actual = ActiveModelSerializers::SerializableResource.new(
+            [@first_post, @second_post], adapter: :json, fields: [:id], include: []
+          ).as_json
+
+          expected = { posts: [{
+            id: 1
+          }, {
+            id: 2
+          }] }
+
+          assert_equal(expected, actual)
+        end
       end
     end
   end