/** * Constructor * * @param Filesystem $filesystem * @param \Magento\Framework\View\Design\Fallback\RulePool $rulePool * @param array $alternativeExtensions */ public function __construct(Filesystem $filesystem, \Magento\Framework\View\Design\Fallback\RulePool $rulePool, array $alternativeExtensions = []) { foreach ($alternativeExtensions as $extension => $newExtensions) { if (!is_string($extension) || !is_array($newExtensions)) { throw new \InvalidArgumentException("\$alternativeExtensions must be an array with format: " . "array('ext1' => array('ext1', 'ext2'), 'ext3' => array(...)]"); } } $this->alternativeExtensions = $alternativeExtensions; parent::__construct($filesystem, $rulePool); }