Run callbacks from object's metaclass [#575 state:resolved]

activesupport/CHANGELOG

@@ -1,5 +1,7 @@
 *Edge*
 
+* Run callbacks from object's metaclass [Josh Peek]
+
 * Add Array#in_groups which splits or iterates over the array in specified number of groups. #579. [Adrian Mugnolo] Example:
   
   a = (1..10).to_a

activesupport/lib/active_support/callbacks.rb

@@ -269,7 +269,15 @@ module ActiveSupport
     #   pass
     #   stop
     def run_callbacks(kind, options = {}, &block)
-      self.class.send("#{kind}_callback_chain").run(self, options, &block)
+      callback_chain_method = "#{kind}_callback_chain"
+
+      # Meta class inherits Class so we don't have to merge it in 1.9
+      if RUBY_VERSION >= '1.9'
+        metaclass.send(callback_chain_method).run(self, options, &block)
+      else
+        callbacks = self.class.send(callback_chain_method) | metaclass.send(callback_chain_method)
+        callbacks.run(self, options, &block)
+      end
     end
   end
 end

activesupport/test/callbacks_test.rb

@@ -84,6 +84,30 @@ class CallbacksTest < Test::Unit::TestCase
   end
 end
 
+class MetaclassCallbacksTest < Test::Unit::TestCase
+  module ModuleWithCallbacks
+    def self.extended(object)
+      object.metaclass.before_save :raise_metaclass_callback_called
+    end
+
+    def module_callback_called?
+      @module_callback_called ||= false
+    end
+
+    def raise_metaclass_callback_called
+      @module_callback_called = true
+    end
+  end
+
+  def test_metaclass_callbacks
+    person = Person.new
+    person.extend(ModuleWithCallbacks)
+    assert !person.module_callback_called?
+    person.save
+    assert person.module_callback_called?
+  end
+end
+
 class ConditionalCallbackTest < Test::Unit::TestCase
   def test_save_conditional_person
     person = ConditionalPerson.new