Add support for yielding from a generator in PrintNode

CHANGELOG

@@ -1,5 +1,6 @@
 # 3.11.0 (2024-XX-XX)
 
+ * Add the possibility to yield from a generator in `PrintNode`
  * Add the `shuffle` filter
  * Add the `singular` and `plural` filters in `StringExtension`
  * Deprecate the second argument of `Twig\Node\Expression\CallExpression::compileArguments()`

src/Node/Expression/AbstractExpression.php

@@ -21,4 +21,8 @@ use Twig\Node\Node;
  */
 abstract class AbstractExpression extends Node
 {
+    public function isGenerator(): bool
+    {
+        return $this->hasAttribute('is_generator') && $this->getAttribute('is_generator');
+    }
 }

src/Node/PrintNode.php

@@ -31,10 +31,9 @@ class PrintNode extends Node implements NodeOutputInterface
 
     public function compile(Compiler $compiler): void
     {
-        $compiler->addDebugInfo($this);
-
         $compiler
-            ->write('yield ')
+            ->addDebugInfo($this)
+            ->write($this->getNode('expr')->isGenerator() ? 'yield from ' : 'yield ')
             ->subcompile($this->getNode('expr'))
             ->raw(";\n")
         ;

src/NodeVisitor/SandboxNodeVisitor.php

@@ -119,7 +119,7 @@ final class SandboxNodeVisitor implements NodeVisitorInterface
     private function wrapNode(Node $node, string $name): void
     {
         $expr = $node->getNode($name);
-        if ($expr instanceof NameExpression || $expr instanceof GetAttrExpression) {
+        if (($expr instanceof NameExpression || $expr instanceof GetAttrExpression) && !$expr->isGenerator()) {
             $node->setNode($name, new CheckToStringNode($expr));
         }
     }

tests/Node/PrintTest.php

@@ -12,7 +12,10 @@ namespace Twig\Tests\Node;
  */
 
 use Twig\Node\Expression\ConstantExpression;
+use Twig\Node\Expression\GetAttrExpression;
+use Twig\Node\Expression\NameExpression;
 use Twig\Node\PrintNode;
+use Twig\Template;
 use Twig\Test\NodeTestCase;
 
 class PrintTest extends NodeTestCase
@@ -30,6 +33,12 @@ class PrintTest extends NodeTestCase
         $tests = [];
         $tests[] = [new PrintNode(new ConstantExpression('foo', 1), 1), "// line 1\nyield \"foo\";"];
 
+        $expr = new NameExpression('foo', 1);
+        $attr = new ConstantExpression('bar', 1);
+        $node = new GetAttrExpression($expr, $attr, null, Template::METHOD_CALL, 1);
+        $node->setAttribute('is_generator', true);
+        $tests[] = [new PrintNode($node, 1), "// line 1\nyield from CoreExtension::getAttribute(\$this->env, \$this->source, (\$context[\"foo\"] ?? null), \"bar\", [], \"method\", false, false, false, 1);"];
+
         return $tests;
     }
 }

tests/NodeVisitor/SandboxTest.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace Twig\Tests\NodeVisitor;
+
+/*
+ * 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.
+ */
+
+use PHPUnit\Framework\TestCase;
+use Twig\Environment;
+use Twig\Loader\ArrayLoader;
+use Twig\Node\CheckToStringNode;
+use Twig\Node\Expression\NameExpression;
+use Twig\Node\ModuleNode;
+use Twig\Node\Node;
+use Twig\Node\PrintNode;
+use Twig\NodeTraverser;
+use Twig\NodeVisitor\SandboxNodeVisitor;
+use Twig\Source;
+
+class SandboxTest extends TestCase
+{
+    public function testGeneratorExpression()
+    {
+        $env = new Environment(new ArrayLoader());
+        $expr = new NameExpression('foo', 1);
+        $expr->setAttribute('is_generator', true);
+        $node = new ModuleNode(new PrintNode($expr, 1), null, new Node(), new Node(), new Node(), new Node([]), new Source('foo', 'foo'));
+        $traverser = new NodeTraverser($env, [new SandboxNodeVisitor($env)]);
+        $node = $traverser->traverse($node);
+
+        $this->assertNotInstanceOf(CheckToStringNode::class, $node->getNode('body')->getNode('expr'));
+        $this->assertSame("// line 1\nyield from (\$context[\"foo\"] ?? null);\n", $env->compile($node->getNode('body')));
+    }
+}