pull request feedback

 - fixed cache listener configuration
 - proper usage of xml configuration

Author: Till Hildebrandt

src/DependencyInjection/Configuration.php

@@ -718,6 +718,7 @@ private function createCachePluginNode()
         $config
             ->fixXmlConfig('method')
             ->fixXmlConfig('respect_response_cache_directive')
+            ->fixXmlConfig('cache_listener')
             ->addDefaultsIfNotSet()
             ->validate()
                 ->ifTrue(function ($config) {
@@ -771,7 +772,7 @@ private function createCachePluginNode()
                 ->end()
                 ->arrayNode('cache_listeners')
                     ->info('A list of service ids to act on the response based on the results of the cache check. Must implement '.CacheListener::class.'. Defaults to an empty array.')
-                    ->beforeNormalization()->ifNull()->thenEmptyArray()->castToArray()->ifEmpty()->thenUnset()->end()
+                    ->beforeNormalization()->castToArray()->end()
                     ->prototype('scalar')
                     ->end()
                 ->end()

tests/Resources/Fixtures/config/full.xml

@@ -62,8 +62,8 @@
             </authentication>
             <cache cache-pool="my_cache_pool" stream-factory="my_other_stream_factory">
                 <config default-ttl="42" cache-lifetime="2592000" hash-algo="sha1" cache-key-generator="null">
-                    <cache-listeners>my_cache_listener_0</cache-listeners>
-                    <cache-listeners>my_cache_listener_1</cache-listeners>
+                    <cache-listener>my_cache_listener_0</cache-listener>
+                    <cache-listener>my_cache_listener_1</cache-listener>
                     <respect-response-cache-directive>X-Foo</respect-response-cache-directive>
                     <method>GET</method>
                     <blacklisted-paths>@/path/not-to-be/cached@</blacklisted-paths>