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, 8 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/validations/associated.rb b/activerecord/lib/active_record/validations/associated.rb
index 32fbaf0a91..b14db85167 100644
--- a/activerecord/lib/active_record/validations/associated.rb
+++ b/activerecord/lib/active_record/validations/associated.rb
@@ -2,10 +2,16 @@ module ActiveRecord
   module Validations
     class AssociatedValidator < ActiveModel::EachValidator #:nodoc:
       def validate_each(record, attribute, value)
-        if Array.wrap(value).reject {|r| r.marked_for_destruction? || r.valid?}.any?
-          record.errors.add(attribute, :invalid, options.merge(:value => value))
+        if Array(value).reject { |r| valid_object?(r) }.any?
+          record.errors.add(attribute, :invalid, options.merge(value: value))
         end
       end
+
+      private
+
+        def valid_object?(record)
+          (record.respond_to?(:marked_for_destruction?) && record.marked_for_destruction?) || record.valid?
+        end
     end
 
     module ClassMethods