Ensure any method sent to RewindableIO reads the original IO object [#1767 state:resolved]

actionpack/lib/action_controller/rack_ext/multipart.rb

@@ -6,8 +6,8 @@ def parse_multipart_with_rewind(env)
           result = parse_multipart_without_rewind(env)
 
           begin
-            env['rack.input'].rewind
-          rescue NoMethodError, Errno::ESPIPE
+            env['rack.input'].rewind if env['rack.input'].respond_to?(:rewind)
+          rescue Errno::ESPIPE
             # Handles exceptions raised by input streams that cannot be rewound
             # such as when using plain CGI under Apache
           end

actionpack/lib/action_controller/rewindable_input.rb

@@ -3,33 +3,17 @@ class RewindableInput
     class RewindableIO < ActiveSupport::BasicObject
       def initialize(io)
         @io = io
-      end
-
-      def read(*args)
-        read_original_io
-        @io.read(*args)
-      end
-
-      def rewind
-        read_original_io
-        @io.rewind
-      end
-
-      def string
-        @string
+        @rewindable = io.is_a?(StringIO)
       end
 
       def method_missing(method, *args, &block)
-        @io.send(method, *args, &block)
-      end
-
-      private
-        def read_original_io
-          unless @string
-            @string = @io.read
-            @io = StringIO.new(@string)
-          end
+        unless @rewindable
+          @io = StringIO.new(@io.read)
+          @rewindable = true
         end
+
+        @io.__send__(method, *args, &block)
+      end
     end
 
     def initialize(app)