Fix observers that use after_find. [#375 state:resolved]

Signed-off-by: Pratik Naik <pratiknaik@gmail.com>

activerecord/lib/active_record/observer.rb

@@ -189,7 +189,7 @@ module ActiveRecord
 
       def add_observer!(klass)
         klass.add_observer(self)
-        klass.class_eval 'def after_find() end' unless klass.respond_to?(:after_find)
+        klass.class_eval 'def after_find() end' unless klass.method_defined?(:after_find)
       end
   end
 end

activerecord/test/cases/lifecycle_test.rb

@@ -2,6 +2,7 @@ require "cases/helper"
 require 'models/topic'
 require 'models/developer'
 require 'models/reply'
+require 'models/minimalistic'
 
 class Topic; def after_find() end end
 class Developer; def after_find() end end
@@ -44,6 +45,14 @@ class TopicObserver < ActiveRecord::Observer
   end
 end
 
+class MinimalisticObserver < ActiveRecord::Observer
+  attr_reader :minimalistic
+
+  def after_find(minimalistic)
+    @minimalistic = minimalistic
+  end
+end
+
 class MultiObserver < ActiveRecord::Observer
   attr_reader :record
 
@@ -134,6 +143,14 @@ class LifecycleTest < ActiveRecord::TestCase
     assert_equal developer.name, multi_observer.record.name
   end
 
+  def test_observing_after_find_when_not_defined_on_the_model
+    observer = MinimalisticObserver.instance
+    assert_equal Minimalistic, MinimalisticObserver.observed_class
+
+    minimalistic = Minimalistic.find(1)
+    assert_equal minimalistic, observer.minimalistic
+  end
+
   def test_invalid_observer
     assert_raise(ArgumentError) { Topic.observers = Object.new; Topic.instantiate_observers }
   end