Non-string results from forwarded methods should be returned vertabim.

activesupport/lib/active_support/multibyte/chars.rb

@@ -106,10 +106,11 @@ def method_missing(method, *args, &block)
           @wrapped_string.__send__(method, *args, &block)
           self
         else
-          chars(@wrapped_string.__send__(method, *args, &block))
+          result = @wrapped_string.__send__(method, *args, &block)
+          result.kind_of?(String) ? chars(result) : result
         end
       end
-      
+
       # Returns +true+ if _obj_ responds to the given method. Private methods are included in the search
       # only if the optional second parameter evaluates to +true+.
       def respond_to?(method, include_private=false)

activesupport/test/multibyte_chars_test.rb

@@ -21,8 +21,9 @@ def assert_equal_codepoints(expected, actual, message=nil)
 end
 
 class String
-  def __string_for_multibyte_testing; self; end
-  def __string_for_multibyte_testing!; self; end
+  def __method_for_multibyte_testing_with_integer_result; 1; end
+  def __method_for_multibyte_testing; 'result'; end
+  def __method_for_multibyte_testing!; 'result'; end
 end
 
 class MultibyteCharsTest < Test::Unit::TestCase
@@ -40,27 +41,31 @@ def test_wraps_the_original_string
 
   def test_should_allow_method_calls_to_string
     assert_nothing_raised do
-      @chars.__string_for_multibyte_testing
+      @chars.__method_for_multibyte_testing
     end
     assert_raises NoMethodError do
       @chars.__unknown_method
     end
   end
 
   def test_forwarded_method_calls_should_return_new_chars_instance
-    assert @chars.__string_for_multibyte_testing.kind_of?(@proxy_class)
-    assert_not_equal @chars.object_id, @chars.__string_for_multibyte_testing.object_id
+    assert @chars.__method_for_multibyte_testing.kind_of?(@proxy_class)
+    assert_not_equal @chars.object_id, @chars.__method_for_multibyte_testing.object_id
   end
 
   def test_forwarded_bang_method_calls_should_return_the_original_chars_instance
-    assert @chars.__string_for_multibyte_testing!.kind_of?(@proxy_class)
-    assert_equal @chars.object_id, @chars.__string_for_multibyte_testing!.object_id
+    assert @chars.__method_for_multibyte_testing!.kind_of?(@proxy_class)
+    assert_equal @chars.object_id, @chars.__method_for_multibyte_testing!.object_id
   end
 
   def test_methods_are_forwarded_to_wrapped_string_for_byte_strings
     assert_equal BYTE_STRING.class, BYTE_STRING.mb_chars.class
   end
 
+  def test_forwarded_method_with_non_string_result_should_be_returned_vertabim
+    assert_equal ''.__method_for_multibyte_testing_with_integer_result, @chars.__method_for_multibyte_testing_with_integer_result
+  end
+
   def test_should_concatenate
     assert_equal 'ab', 'a'.mb_chars + 'b'
     assert_equal 'ab', 'a' + 'b'.mb_chars