Discard what the non-selected branch of a guard tag registers on the parser

CHANGELOG

@@ -2,6 +2,7 @@
 
  * Reject a deprecated `Template` instance created by another environment in `Environment::resolveTemplate()`
  * Fix a compilation error inside an `autoescape` tag leaking its escaping strategy into the next compiled template
+ * Fix the non-selected branch of a `guard` tag registering its parent, blocks, and macros
  * Speed up reading object attributes backed by getters or class constants
  * Fix the sandbox not reporting the line of a rejected `guard` tag
 

src/Parser.php

@@ -159,14 +159,19 @@ class Parser
         return $this->ignoreUnknownTwigCallables;
     }
 
+    /**
+     * Parses a discarded part of the template: what it registers (parent, blocks, macros, ...) is discarded as well.
+     */
     public function subparseIgnoreUnknownTwigCallables($test, bool $dropNeedle = false): void
     {
         $previous = $this->ignoreUnknownTwigCallables;
+        $state = [$this->parent, $this->blocks, $this->documentationTargets, $this->macros, $this->importedSymbols, $this->traits, $this->embeddedTemplates];
         $this->ignoreUnknownTwigCallables = true;
         try {
             $this->subparse($test, $dropNeedle);
         } finally {
             $this->ignoreUnknownTwigCallables = $previous;
+            [$this->parent, $this->blocks, $this->documentationTargets, $this->macros, $this->importedSymbols, $this->traits, $this->embeddedTemplates] = $state;
         }
     }
 

src/TokenParser/GuardTokenParser.php

@@ -55,7 +55,11 @@ final class GuardTokenParser extends AbstractTokenParser
         $else = new EmptyNode();
         if ('else' === $stream->next()->getValue()) {
             $stream->expect(Token::BLOCK_END_TYPE);
-            $else = $this->parser->subparse([$this, 'decideGuardEnd'], true);
+            if ($exists) {
+                $this->parser->subparseIgnoreUnknownTwigCallables([$this, 'decideGuardEnd'], true);
+            } else {
+                $else = $this->parser->subparse([$this, 'decideGuardEnd'], true);
+            }
         }
         $stream->expect(Token::BLOCK_END_TYPE);
 

tests/Fixtures/tags/guard/discarded_branch.test

@@ -0,0 +1,9 @@
+--TEST--
+"guard" ignores the blocks and macros defined in the discarded branch
+--TEMPLATE--
+{% guard function constant %}{% else %}{% block discarded %}{% endblock %}{% macro discarded() %}{% endmacro %}{% endguard %}
+{{ block('discarded') is defined ? 'NEVER' : 'no block' }} {{ _self.discarded is defined ? 'NEVER' : 'no macro' }}
+--DATA--
+return []
+--EXPECT--
+no block no macro

tests/Fixtures/tags/guard/discarded_parent.legacy.test

@@ -0,0 +1,15 @@
+--TEST--
+"guard" ignores the parent defined in the discarded branch
+--DEPRECATION--
+Since twig/twig 3.28: Using the "extends" tag outside the root of a template is deprecated in index.twig at line 2.
+--TEMPLATE--
+{% guard function foobar %}{% extends "never.twig" %}{% else %}{% extends "layout.twig" %}{% endguard %}
+{% block content %}content{% endblock %}
+--TEMPLATE(layout.twig)--
+layout {{ block('content') }}
+--TEMPLATE(never.twig)--
+NEVER
+--DATA--
+return []
+--EXPECT--
+layout content