Ruby 1.9: flushing the output buffer preserves its encoding

actionpack/lib/action_view/helpers/capture_helper.rb

@@ -124,7 +124,11 @@ module ActionView
 
       # Use an alternate output buffer for the duration of the block.
       # Defaults to a new empty string.
-      def with_output_buffer(buf = '') #:nodoc:
+      def with_output_buffer(buf = nil) #:nodoc:
+        unless buf
+          buf = ''
+          buf.force_encoding(output_buffer.encoding) if buf.respond_to?(:force_encoding)
+        end
         self.output_buffer, old_buffer = buf, output_buffer
         yield
         output_buffer
@@ -134,9 +138,12 @@ module ActionView
 
       # Add the output buffer to the response body and start a new one.
       def flush_output_buffer #:nodoc:
-        if output_buffer && output_buffer != ''
+        if output_buffer && !output_buffer.empty?
           response.body_parts << output_buffer
-          self.output_buffer = ''
+          new = ''
+          new.force_encoding(output_buffer.encoding) if new.respond_to?(:force_encoding)
+          self.output_buffer = new
+          nil
         end
       end
     end

actionpack/test/template/output_buffer_test.rb

@@ -38,6 +38,17 @@ class OutputBufferTest < ActionController::TestCase
     assert_equal ['foo', 'bar'], body_parts
   end
 
+  if '1.9'.respond_to?(:force_encoding)
+    test 'flushing preserves output buffer encoding' do
+      original_buffer = ' '.force_encoding(Encoding::EUC_JP)
+      @controller.template.output_buffer = original_buffer
+      @controller.template.flush_output_buffer
+      assert_equal ['foo', original_buffer], body_parts
+      assert_not_equal original_buffer, output_buffer
+      assert_equal Encoding::EUC_JP, output_buffer.encoding
+    end
+  end
+
   protected
     def output_buffer
       @controller.template.output_buffer