feature #2341 feature #2045 Adds Twig_NodeCaptureInterface for nodes that capture all output (brandonkelly)

This PR was submitted for the 2.x branch but it was merged into the 1.x branch instead (closes #2341).

Discussion
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feature #2045 Adds Twig_NodeCaptureInterface for nodes that capture all output

This implements the feature originally suggested by #2045, but specifically in the manner suggested by #2340, which I think is more consistent with existing Twig code.

Commits
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bc6a9133 feature #2045 Adds Twig_NodeCaptureInterface for nodes that capture all output

lib/Twig/Node/Set.php

@@ -14,7 +14,7 @@
  *
  * @author Fabien Potencier <fabien@symfony.com>
  */
-class Twig_Node_Set extends Twig_Node
+class Twig_Node_Set extends Twig_Node implements Twig_NodeCaptureInterface
 {
     public function __construct($capture, Twig_NodeInterface $names, Twig_NodeInterface $values, $lineno, $tag = null)
     {

lib/Twig/NodeCaptureInterface.php

@@ -0,0 +1,19 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) 2010 Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ * Represents a node that will capture any nested displayable nodes.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+interface Twig_NodeCaptureInterface
+{
+}

lib/Twig/Parser.php

@@ -386,8 +386,8 @@ class Twig_Parser implements Twig_ParserInterface
             throw new Twig_Error_Syntax('A template that extends another one cannot include contents outside Twig blocks. Did you forget to put the contents inside a {% block %} tag?', $node->getTemplateLine(), $this->stream->getSourceContext());
         }
 
-        // bypass "set" nodes as they "capture" the output
-        if ($node instanceof Twig_Node_Set) {
+        // bypass nodes that will "capture" the output
+        if ($node instanceof Twig_NodeCaptureInterface) {
             return $node;
         }