BufferedLogger#add doesn't modify the message argument. Closes #9702.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@7643 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activesupport/CHANGELOG

 *SVN*
 
+* BufferedLogger#add doesn't modify the message argument.  #9702 [eigentone]
+
 * Added ActiveSupport::BufferedLogger as a duck-typing alternative (albeit with no formatter) to the Ruby Logger, which provides a very nice speed bump (inspired by Ezra's buffered logger) [DHH]
 
 * Object#instance_exec produces fewer garbage methods.  [Mauricio Fernandez]

activesupport/lib/active_support/buffered_logger.rb

@@ -52,7 +52,9 @@ def initialize(log, level = DEBUG)
     def add(severity, message = nil, progname = nil, &block)
       return if @level > severity
       message = message || (block && block.call) || progname
-      message << "\n" unless message[-1] == ?\n
+      # If a newline is nessesary then create a new message end with a new line.
+      # Ensures that the original message is not mutated.
+      message = "#{message}\n" unless message[-1] == ?\n
       @buffer << message
       flush if auto_flushing
       message

activesupport/test/buffered_logger_test.rb

@@ -38,4 +38,10 @@ def test_should_not_evaluate_block_if_message_wont_be_logged
     @logger.add(Logger::DEBUG) {evaluated = true}
     assert evaluated == false  
   end
+  
+  def test_should_not_mutate_message
+    message_copy = @message.dup
+    @logger.info @message
+    assert_equal message_copy, @message
+  end
 end