conneg.rb in rack-linkeddata-0.1.1

- old
+ new

@@ -3,10 +3,11 @@
   # Rack middleware for Linked Data content negotiation.
   #
   # @see http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/
   class ContentNegotiation
     DEFAULT_CONTENT_TYPE = "text/plain" # N-Triples
+    VARY = {'Vary' => 'Accept'}.freeze
 
     # @return [#call]
     attr_reader :app
 
     # @return [Hash{Symbol => Object}]
@@ -49,11 +50,16 @@
     # @param  [Hash{String => Object}] headers
     # @param  [RDF::Enumerable]        body
     # @return [Array(Integer, Hash, #each)]
     def serialize(env, status, headers, body)
       writer, content_type = find_writer(env)
-      writer ? [status, headers.merge('Content-Type' => content_type), [writer.dump(body)]] : not_acceptable
+      if writer
+        headers = headers.merge(VARY).merge('Content-Type' => content_type) # FIXME: don't overwrite existing Vary headers
+        [status, headers, [writer.dump(body)]]
+      else
+        not_acceptable
+      end
     end
 
     ##
     # Returns an `RDF::Writer` class for the given `env`.
     #
@@ -121,10 +127,10 @@
     # Outputs an HTTP `406 Not Acceptable` response.
     #
     # @param  [String, #to_s] message
     # @return [Array(Integer, Hash, #each)]
     def not_acceptable(message = nil)
-      http_error(406, message)
+      http_error(406, message, VARY)
     end
 
     ##
     # Outputs an HTTP `4xx` or `5xx` response.
     #