Improve support for non Active Record objects on `validates_associated`

Skipping `marked_for_destruction?` when the associated object does not responds
to it make easier to validate virtual associations built on top of Active Model
objects and/or serialized objects that implement a `valid?` instance method.

1 files changed, 12 insertions, 0 deletions

diff --git a/activerecord/test/cases/validations/association_validation_test.rb b/activerecord/test/cases/validations/association_validation_test.rb
index bff5ffa65e..584a3dc0d8 100644
--- a/activerecord/test/cases/validations/association_validation_test.rb
+++ b/activerecord/test/cases/validations/association_validation_test.rb
@@ -45,6 +45,18 @@ class AssociationValidationTest < ActiveRecord::TestCase
     assert t.valid?
   end
 
+  def test_validates_associated_without_marked_for_destruction
+    reply = Class.new do
+      def valid?
+        true
+      end
+    end
+    Topic.validates_associated(:replies)
+    t = Topic.new
+    t.define_singleton_method(:replies) { [reply.new] }
+    assert t.valid?
+  end
+
   def test_validates_associated_with_custom_message_using_quotes
     Reply.validates_associated :topic, :message=> "This string contains 'single' and \"double\" quotes"
     Topic.validates_presence_of :content