/**
  * @param ScaffolderConfig $config
  */
 public function perform(ScaffolderConfig $config)
 {
     /**
      * @var RequestDeclaration $declaration
      */
     $declaration = $this->createDeclaration(['parent' => RequestFilter::class]);
     $declaration->setMapping($config->getMapping(static::ELEMENT));
     foreach ($this->option('field') as $field) {
         list($field, $type, $source, $origin) = $this->parseField($field);
         $declaration->declareField($field, $type, $source, $origin);
     }
     $this->writeDeclaration($declaration->normalize());
 }