Automatically include ArraySerializer in ActiveRecord::Relation

fixes #81

lib/active_model/serializer.rb

@@ -524,9 +524,15 @@ module ActiveModel
   end
 end
 
-class Array
-  # Array uses ActiveModel::ArraySerializer.
+module ActiveModel::ArraySerializerSupport
   def active_model_serializer
     ActiveModel::ArraySerializer
   end
 end
+
+Array.send(:include, ActiveModel::ArraySerializerSupport)
+
+ActiveSupport.on_load(:active_record) do
+  ActiveRecord::Relation.send(:include, ActiveModel::ArraySerializerSupport)
+end
+

test/serializer_support_test.rb

@@ -4,8 +4,27 @@ class RandomModel
   include ActiveModel::SerializerSupport
 end
 
+class RandomModelCollection
+  include ActiveModel::ArraySerializerSupport
+end
+
+module ActiveRecord
+  class Relation
+  end
+end
+
 class SerializerSupportTest < ActiveModel::TestCase
   test "it returns nil if no serializer exists" do
     assert_equal nil, RandomModel.new.active_model_serializer
   end
-end
+
+  test "it returns ArraySerializer for a collection" do
+    assert_equal ActiveModel::ArraySerializer, RandomModelCollection.new.active_model_serializer
+  end
+
+  test "it automatically includes array_serializer in active_record/relation" do
+    ActiveSupport.run_load_hooks(:active_record)
+    assert_equal ActiveModel::ArraySerializer, ActiveRecord::Relation.new.active_model_serializer
+  end
+end
+