Make alias_method_chain complain about duplicate aliases. Previously

repeated calls to alias_method_chain would cause infinite loops.

Signed-Off-By: Michael Koziarski <michael@koziarski.com>

2 files changed, 18 insertions, 1 deletions

diff --git a/activesupport/lib/active_support/core_ext/module/aliasing.rb b/activesupport/lib/active_support/core_ext/module/aliasing.rb
index 1894e3b0a2..cb7d4c1c3c 100644
--- a/activesupport/lib/active_support/core_ext/module/aliasing.rb
+++ b/activesupport/lib/active_support/core_ext/module/aliasing.rb
@@ -28,6 +28,10 @@ class Module
     
     with_method, without_method = "#{aliased_target}_with_#{feature}#{punctuation}", "#{aliased_target}_without_#{feature}#{punctuation}"
     
+    if method_defined?(without_method) || private_method_defined?(without_method)
+      raise NameError, "#{with_method} is already in #{target}'s alias chain."
+    end
+    
     alias_method without_method, target
     alias_method target, with_method
     
diff --git a/activesupport/test/core_ext/module_test.rb b/activesupport/test/core_ext/module_test.rb
index ecdea38d44..d983044fc3 100644
--- a/activesupport/test/core_ext/module_test.rb
+++ b/activesupport/test/core_ext/module_test.rb
@@ -166,6 +166,19 @@ class MethodAliasingTest < Test::Unit::TestCase
     assert_equal 'bar_with_baz', @instance.bar
     assert_equal 'bar', @instance.bar_without_baz
   end
+  
+  def test_alias_method_chain_complains_the_second_time
+    FooClassWithBarMethod.class_eval do
+      def bar_with_magic; end
+      alias_method_chain :bar, :magic
+    end
+    
+    assert_raise(NameError) do
+      FooClassWithBarMethod.class_eval do
+        alias_method_chain :bar, :magic
+      end
+    end
+  end
 
   def test_alias_method_chain_with_punctuation_method
     FooClassWithBarMethod.class_eval do
@@ -289,5 +302,5 @@ class MethodAliasingTest < Test::Unit::TestCase
 
     assert_equal 'duck_with_orange', @instance.duck
     assert FooClassWithBarMethod.public_method_defined?(:duck)
-  end
+  end  
 end