adding support for the ?? operator

CHANGELOG

@@ -1,5 +1,6 @@
 * 1.23.4 (2016-XX-XX)
 
+ * adding support for the ?? operator
  * fixed the defined test when used on a constant, a map, or a sequence
  * undeprecated _self (should only be used to get the template name, not the template instance)
  * fixed parsing on PHP7

doc/templates.rst

@@ -808,6 +808,13 @@ The following operators don't fit into any of the other categories:
       {{ foo ?: 'no' }} is the same as {{ foo ? foo : 'no' }}
       {{ foo ? 'yes' }} is the same as {{ foo ? 'yes' : '' }}
 
+* ``??``: The null-coalescing operator:
+
+  .. code-block:: jinja
+
+      {# returns the value of foo if it is defined and not null, 'no' otherwise #}
+      {{ foo ?? 'no' }}
+
 String Interpolation
 ~~~~~~~~~~~~~~~~~~~~
 

lib/Twig/Extension/Core.php

@@ -261,6 +261,7 @@ class Twig_Extension_Core extends Twig_Extension
                 'is' => array('precedence' => 100, 'callable' => array($this, 'parseTestExpression'), 'associativity' => Twig_ExpressionParser::OPERATOR_LEFT),
                 'is not' => array('precedence' => 100, 'callable' => array($this, 'parseNotTestExpression'), 'associativity' => Twig_ExpressionParser::OPERATOR_LEFT),
                 '**' => array('precedence' => 200, 'class' => 'Twig_Node_Expression_Binary_Power', 'associativity' => Twig_ExpressionParser::OPERATOR_RIGHT),
+                '??' => array('precedence' => 300, 'class' => 'Twig_Node_Expression_NullCoalesce', 'associativity' => Twig_ExpressionParser::OPERATOR_RIGHT),
             ),
         );
     }

lib/Twig/Node/Expression/NullCoalesce.php

@@ -0,0 +1,23 @@
+<?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.
+ */
+class Twig_Node_Expression_NullCoalesce extends Twig_Node_Expression_Conditional
+{
+    public function __construct(Twig_NodeInterface $left, Twig_NodeInterface $right, $lineno)
+    {
+        $test = new Twig_Node_Expression_Binary_And(
+            new Twig_Node_Expression_Test_Defined(clone $left, 'defined', new Twig_Node(), $left->getLine()),
+            new Twig_Node_Expression_Unary_Not(new Twig_Node_Expression_Test_Null($left, 'null', new Twig_Node(), $left->getLine()), $left->getLine()),
+            $left->getLine()
+        );
+
+        parent::__construct($test, $left, $right, $lineno);
+    }
+}

test/Twig/Tests/Fixtures/tests/null_coalesce.test

@@ -0,0 +1,30 @@
+--TEST--
+Twig supports the ?? operator
+--TEMPLATE--
+{{ 'OK' ?? 'KO' }}
+{{ null ?? 'OK' }}
+{{ bar ?? 'KO' }}
+{{ baz ?? 'OK' }}
+{{ foo.bar ?? 'KO' }}
+{{ foo.missing ?? 'OK' }}
+{{ foo.bar.baz.missing ?? 'OK' }}
+{{ foo['bar'] ?? 'KO' }}
+{{ foo['missing'] ?? 'OK' }}
+{{ nope ?? nada ?? 'OK' }}
+{{ 1 + nope ?? nada ?? 2 }}
+{{ 1 + nope ?? 3 + nada ?? 2 }}
+--DATA--
+return array('bar' => 'OK', 'foo' => array('bar' => 'OK'))
+--EXPECT--
+OK
+OK
+OK
+OK
+OK
+OK
+OK
+OK
+OK
+OK
+3
+6