Fix read_attribute_for_serialization not seeing parent serializer methods

Fixes #1653, #1658, #1660

Define "scope_name" on instance singleton, not all instances

test/serializers/read_attribute_for_serialization_test.rb

@@ -0,0 +1,79 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    class ReadAttributeForSerializationTest < ActiveSupport::TestCase
+      # https://github.com/rails-api/active_model_serializers/issues/1653
+      class Parent < ActiveModelSerializers::Model
+        attr_accessor :id
+      end
+      class Child < Parent
+        attr_accessor :name
+      end
+      class ParentSerializer < ActiveModel::Serializer
+        attributes :$id
+
+        define_method(:$id) do
+          object.id
+        end
+      end
+      class ChildSerializer < ParentSerializer
+        attributes :name
+      end
+
+      def test_child_serializer_calls_dynamic_method_in_parent_serializer
+        parent = ParentSerializer.new(Parent.new(id: 5))
+        child  = ChildSerializer.new(Child.new(id: 6, name: 'Child'))
+        assert_equal 5, parent.read_attribute_for_serialization(:$id)
+        assert_equal 6, child.read_attribute_for_serialization(:$id)
+      end
+
+      # https://github.com/rails-api/active_model_serializers/issues/1658
+      class ErrorResponse < ActiveModelSerializers::Model
+        attr_accessor :error
+      end
+      class ApplicationSerializer < ActiveModel::Serializer
+        attributes :status
+
+        def status
+          object.try(:errors).blank? && object.try(:error).blank?
+        end
+      end
+      class ErrorResponseSerializer < ApplicationSerializer
+        attributes :error
+      end
+      class ErrorResponseWithSuperSerializer < ApplicationSerializer
+        attributes :error
+
+        def success
+          super
+        end
+      end
+
+      def test_child_serializer_with_error_attribute
+        error = ErrorResponse.new(error: 'i have an error')
+        serializer = ErrorResponseSerializer.new(error)
+        serializer_with_super = ErrorResponseWithSuperSerializer.new(error)
+        assert_equal false, serializer.read_attribute_for_serialization(:status)
+        assert_equal false, serializer_with_super.read_attribute_for_serialization(:status)
+      end
+
+      def test_child_serializer_with_errors
+        error = ErrorResponse.new
+        error.errors.add(:invalid, 'i am not valid')
+        serializer = ErrorResponseSerializer.new(error)
+        serializer_with_super = ErrorResponseWithSuperSerializer.new(error)
+        assert_equal false, serializer.read_attribute_for_serialization(:status)
+        assert_equal false, serializer_with_super.read_attribute_for_serialization(:status)
+      end
+
+      def test_child_serializer_no_error_attribute_or_errors
+        error = ErrorResponse.new
+        serializer = ErrorResponseSerializer.new(error)
+        serializer_with_super = ErrorResponseWithSuperSerializer.new(error)
+        assert_equal true, serializer.read_attribute_for_serialization(:status)
+        assert_equal true, serializer_with_super.read_attribute_for_serialization(:status)
+      end
+    end
+  end
+end