Removed metaclass from the has_many dependency destroy method. Fixes #2954

activerecord/lib/active_record/associations/builder/belongs_to.rb

@@ -33,8 +33,10 @@ def add_counter_cache_callbacks(reflection)
 
         method_name = "belongs_to_counter_cache_before_destroy_for_#{name}"
         mixin.redefine_method(method_name) do
-          record = send(name)
-          record.class.decrement_counter(cache_column, record.id) unless record.nil?
+          unless marked_for_destruction?
+            record = send(name)
+            record.class.decrement_counter(cache_column, record.id) unless record.nil?
+          end
         end
         model.before_destroy(method_name)
 

activerecord/lib/active_record/associations/builder/has_many.rb

@@ -31,12 +31,7 @@ def define_destroy_dependency_method
         mixin.redefine_method(dependency_method_name) do
           send(name).each do |o|
             # No point in executing the counter update since we're going to destroy the parent anyway
-            counter_method = ('belongs_to_counter_cache_before_destroy_for_' + self.class.name.downcase).to_sym
-            if o.respond_to?(counter_method)
-              class << o
-                self
-              end.send(:define_method, counter_method, Proc.new {})
-            end
+            o.mark_for_destruction
           end
 
           send(name).delete_all