issue #15: fix crash when using lazy queues

The message properties can be either in plain text or byte encoded. It
seems lazy queues prefer to use the latter.

The deduplication queue was not handling encoded message
properties. Therefore it was crashing when trying to fetch the message
properties headers.

Signed-off-by: Matteo Cafasso <[email protected]>

Author: noxdafox

lib/common.ex

@@ -16,6 +16,7 @@ defmodule RabbitMQ.MessageDeduplicationPlugin.Common do
 
   require RabbitMQ.MessageDeduplicationPlugin.Cache
 
+  alias :rabbit_binary_parser, as: RabbitBinaryParser
   alias RabbitMQ.MessageDeduplicationPlugin.Cache, as: MessageCache
 
   defrecord :content, extract(
@@ -58,14 +59,13 @@ defmodule RabbitMQ.MessageDeduplicationPlugin.Common do
   Retrieve the given header from the message.
   """
   @spec message_header(basic_message, String.t) :: String.t | nil
-  def message_header(message, header) do
-    basic_message(content: content(properties: properties)) = message
+  def message_header(basic_message(content: message_content), header) do
+    message_content = RabbitBinaryParser.ensure_content_decoded(message_content)
 
-    case properties do
+    case content(message_content, :properties) do
       basic_properties(headers: headers) when is_list(headers) ->
         rabbit_keyfind(headers, header)
       basic_properties(headers: :undefined) -> nil
-      :undefined -> nil
     end
   end