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   1  <?php
   2  
   3  /*
   4   * This file is part of Twig.
   5   *
   6   * (c) Fabien Potencier
   7   *
   8   * For the full copyright and license information, please view the LICENSE
   9   * file that was distributed with this source code.
  10   */
  11  
  12  namespace Twig\Node\Expression;
  13  
  14  use Twig\Compiler;
  15  use Twig\Node\Expression\Binary\AndBinary;
  16  use Twig\Node\Expression\Test\DefinedTest;
  17  use Twig\Node\Expression\Test\NullTest;
  18  use Twig\Node\Expression\Unary\NotUnary;
  19  use Twig\Node\Node;
  20  
  21  class NullCoalesceExpression extends ConditionalExpression
  22  {
  23      public function __construct(Node $left, Node $right, int $lineno)
  24      {
  25          $test = new DefinedTest(clone $left, 'defined', new Node(), $left->getTemplateLine());
  26          // for "block()", we don't need the null test as the return value is always a string
  27          if (!$left instanceof BlockReferenceExpression) {
  28              $test = new AndBinary(
  29                  $test,
  30                  new NotUnary(new NullTest($left, 'null', new Node(), $left->getTemplateLine()), $left->getTemplateLine()),
  31                  $left->getTemplateLine()
  32              );
  33          }
  34  
  35          parent::__construct($test, $left, $right, $lineno);
  36      }
  37  
  38      public function compile(Compiler $compiler)
  39      {
  40          /*
  41           * This optimizes only one case. PHP 7 also supports more complex expressions
  42           * that can return null. So, for instance, if log is defined, log("foo") ?? "..." works,
  43           * but log($a["foo"]) ?? "..." does not if $a["foo"] is not defined. More advanced
  44           * cases might be implemented as an optimizer node visitor, but has not been done
  45           * as benefits are probably not worth the added complexity.
  46           */
  47          if ($this->getNode('expr2') instanceof NameExpression) {
  48              $this->getNode('expr2')->setAttribute('always_defined', true);
  49              $compiler
  50                  ->raw('((')
  51                  ->subcompile($this->getNode('expr2'))
  52                  ->raw(') ?? (')
  53                  ->subcompile($this->getNode('expr3'))
  54                  ->raw('))')
  55              ;
  56          } else {
  57              parent::compile($compiler);
  58          }
  59      }
  60  }
  61  
  62  class_alias('Twig\Node\Expression\NullCoalesceExpression', 'Twig_Node_Expression_NullCoalesce');