--- /dev/null
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ * Twig_BaseNodeVisitor can be used to make node visitors compatible with Twig 1.x and 2.x.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+abstract class Twig_BaseNodeVisitor implements Twig_NodeVisitorInterface
+{
+ final public function enterNode(Twig_NodeInterface $node, Twig_Environment $env)
+ {
+ if (!$node instanceof Twig_Node) {
+ throw new LogicException('Twig_BaseNodeVisitor only supports Twig_Node instances.');
+ }
+
+ return $this->doEnterNode($node, $env);
+ }
+
+ final public function leaveNode(Twig_NodeInterface $node, Twig_Environment $env)
+ {
+ if (!$node instanceof Twig_Node) {
+ throw new LogicException('Twig_BaseNodeVisitor only supports Twig_Node instances.');
+ }
+
+ return $this->doLeaveNode($node, $env);
+ }
+
+ /**
+ * Called before child nodes are visited.
+ *
+ * @return Twig_Node The modified node
+ */
+ abstract protected function doEnterNode(Twig_Node $node, Twig_Environment $env);
+
+ /**
+ * Called after child nodes are visited.
+ *
+ * @return Twig_Node|false The modified node or false if the node must be removed
+ */
+ abstract protected function doLeaveNode(Twig_Node $node, Twig_Environment $env);
+}