Support customer array serializer

lib/active_model/serializer.rb

@@ -58,7 +58,11 @@ end
       if RUBY_VERSION >= '2.0'
         def serializer_for(resource)
           if resource.respond_to?(:to_ary)
-            ArraySerializer
+            if Object.constants.include?(:ArraySerializer)
+              ::ArraySerializer
+            else
+              ArraySerializer
+            end
           else
             begin
               Object.const_get "#{resource.class.name}Serializer"
@@ -70,7 +74,11 @@ end
       else
         def serializer_for(resource)
           if resource.respond_to?(:to_ary)
-            ArraySerializer
+            if Object.constants.include?(:ArraySerializer)
+              ::ArraySerializer
+            else
+              ArraySerializer
+            end
           else
             "#{resource.class.name}Serializer".safe_constantize
           end

test/unit/active_model/array_serializer/serialization_test.rb

@@ -9,7 +9,7 @@ module ActiveModel
       end
 
       def test_serializer_for_array_returns_appropriate_type
-        assert_kind_of ArraySerializer, @serializer
+        assert_kind_of ActiveModel::ArraySerializer, @serializer
       end
 
       def test_array_serializer_serializes_simple_objects
@@ -18,6 +18,23 @@ module ActiveModel
       end
     end
 
+    class CustomArraySerializerSupport < Minitest::Test
+      def setup
+        Object.const_set(:ArraySerializer, Class.new{ def initialize(*); end })
+
+        array = [1, 2, 3]
+        @serializer = Serializer.serializer_for(array).new(array)
+      end
+
+      def teardown
+        Object.send(:remove_const, :ArraySerializer)
+      end
+
+      def test_serializer_for_array_returns_appropriate_type
+        assert_kind_of ::ArraySerializer, @serializer
+      end
+    end
+
     class ModelSerializationTest < Minitest::Test
       def test_array_serializer_serializes_models
         array = [Profile.new({ name: 'Name 1', description: 'Description 1', comments: 'Comments 1' }),