Fix support for ignoring syntax erros in an undefined handler in guard

src/ExpressionParser.php

@@ -799,7 +799,17 @@ class ExpressionParser
 
     private function getFunction(string $name, int $line): TwigFunction
     {
-        if (!$function = $this->env->getFunction($name)) {
+        try {
+            $function = $this->env->getFunction($name);
+        } catch (SyntaxError $e) {
+            if (!$this->parser->shouldIgnoreUnknownTwigCallables()) {
+                throw $e;
+            }
+
+            $function = null;
+        }
+
+        if (!$function) {
             if ($this->parser->shouldIgnoreUnknownTwigCallables()) {
                 return new TwigFunction($name, fn () => '');
             }
@@ -819,7 +829,16 @@ class ExpressionParser
 
     private function getFilter(string $name, int $line): TwigFilter
     {
-        if (!$filter = $this->env->getFilter($name)) {
+        try {
+            $filter = $this->env->getFilter($name);
+        } catch (SyntaxError $e) {
+            if (!$this->parser->shouldIgnoreUnknownTwigCallables()) {
+                throw $e;
+            }
+
+            $filter = null;
+        }
+        if (!$filter) {
             if ($this->parser->shouldIgnoreUnknownTwigCallables()) {
                 return new TwigFilter($name, fn () => '');
             }

tests/Fixtures/tags/guard/throwing_handler.test

@@ -0,0 +1,22 @@
+--TEST--
+"guard" creates a compilation time condition on Twig callables availability
+--TEMPLATE--
+{% guard filter throwing_undefined_filter %}
+    NEVER
+    {{ 'a'|throwing_undefined_filter }}
+{% else -%}
+    The throwing_undefined_filter filter doesn't exist
+{% endguard %}
+
+{% guard function throwing_undefined_function -%}
+    NEVER
+    {{ throwing_undefined_function() }}
+{% else -%}
+    The throwing_undefined_function function doesn't exist
+{% endguard %}
+--DATA--
+return []
+--EXPECT--
+The throwing_undefined_filter filter doesn't exist
+
+The throwing_undefined_function function doesn't exist

tests/IntegrationTest.php

@@ -12,6 +12,7 @@ namespace Twig\Tests;
  */
 
 use Twig\DeprecatedCallableInfo;
+use Twig\Error\SyntaxError;
 use Twig\Extension\AbstractExtension;
 use Twig\Extension\DebugExtension;
 use Twig\Extension\SandboxExtension;
@@ -49,6 +50,32 @@ class IntegrationTest extends IntegrationTestCase
         ];
     }
 
+    protected function getUndefinedFunctionCallbacks(): array
+    {
+        return [
+            static function (string $name) {
+                if ('throwing_undefined_function' === $name) {
+                    throw new SyntaxError('This function is undefined in the tests.');
+                }
+
+                return false;
+            },
+        ];
+    }
+
+    protected function getUndefinedTokenParserCallbacks(): array
+    {
+        return [
+            static function (string $name) {
+                if ('throwing_undefined_filter' === $name) {
+                    throw new SyntaxError('This filter is undefined in the tests.');
+                }
+
+                return false;
+            },
+        ];
+    }
+
     protected static function getFixturesDirectory(): string
     {
         return __DIR__.'/Fixtures/';