Unset fields if no nested fields are defined

DependencyInjection/Configuration.php

@@ -334,6 +334,10 @@ class Configuration implements ConfigurationInterface
         $childrenNode = $node
             ->useAttributeAsKey('name')
             ->prototype('array')
+                ->validate()
+                ->ifTrue(function($v) { return isset($v['fields']) && empty($v['fields']); })
+                    ->then(function($v) { unset($v['fields']); return $v; })
+                ->end()
                 ->treatNullLike(array())
                 ->addDefaultsIfNotSet()
                 ->children();

Tests/DependencyInjection/ConfigurationTest.php

@@ -103,4 +103,34 @@ class ConfigurationTest extends \PHPUnit_Framework_TestCase
 
         $this->assertEquals('http://www.github.com/', $configuration['clients']['default']['servers'][0]['url']);
     }
+
+    public function testEmptyFieldsIndexIsUnset()
+    {
+        $config = array(
+            'indexes' => array(
+                'test' => array(
+                    'types' => array(
+                        'test' => array(
+                            'mappings' => array(
+                                'title' => array(
+                                    'type' => 'string',
+                                    'fields' => array(
+                                        'autocomplete' => null
+                                    )
+                                ),
+                                'content' => null
+                            )
+                        )
+                    )
+                )
+            )
+        );
+
+        $processor = new Processor();
+
+        $configuration = $processor->processConfiguration(new Configuration(array($config)), array($config));
+
+        $this->assertArrayNotHasKey('fields', $configuration['indexes']['test']['types']['test']['mappings']['content']);
+        $this->assertArrayHasKey('fields', $configuration['indexes']['test']['types']['test']['mappings']['title']);
+    }
 }