fixed embedded templates starting with a BOM

CHANGELOG

@@ -1,5 +1,6 @@
 * 1.37.0 (2019-XX-XX)
 
+ * fixed embedded templates starting with a BOM
  * fixed using a Twig_TemplateWrapper instance as an argument to extends
  * switched generated code to use the PHP short array notation
  * dropped PHP 5.3 support

lib/Twig/Parser.php

@@ -382,7 +382,11 @@ class Twig_Parser implements Twig_ParserInterface
             (!$node instanceof Twig_Node_Text && !$node instanceof Twig_Node_BlockReference && $node instanceof Twig_NodeOutputInterface)
         ) {
             if (false !== strpos((string) $node, chr(0xEF).chr(0xBB).chr(0xBF))) {
-                throw new Twig_Error_Syntax('A template that extends another one cannot start with a byte order mark (BOM); it must be removed.', $node->getTemplateLine(), $this->stream->getSourceContext());
+                $t = substr($node->getAttribute('data'), 3);
+                if ('' === $t || ctype_space($t)) {
+                    // bypass empty nodes starting with a BOM
+                    return;
+                }
             }
 
             throw new Twig_Error_Syntax('A template that extends another one cannot include content outside Twig blocks. Did you forget to put the content inside a {% block %} tag?', $node->getTemplateLine(), $this->stream->getSourceContext());

test/Twig/Tests/ParserTest.php

@@ -99,13 +99,21 @@ class Twig_Tests_ParserTest extends \PHPUnit\Framework\TestCase
     }
 
     /**
-     * @expectedException Twig_Error_Syntax
-     * @expectedExceptionMessage A template that extends another one cannot start with a byte order mark (BOM); it must be removed at line 1
+     * @dataProvider getFilterBodyNodesWithBOMData
      */
-    public function testFilterBodyNodesWithBOM()
+    public function testFilterBodyNodesWithBOM($emptyNode)
     {
-        $parser = $this->getParser();
-        $parser->filterBodyNodes(new Twig_Node_Text(chr(0xEF).chr(0xBB).chr(0xBF), 1));
+        $this->assertSame(null, $this->getParser()->filterBodyNodes(new Twig_Node_Text(chr(0xEF).chr(0xBB).chr(0xBF).$emptyNode, 1)));
+    }
+
+    public function getFilterBodyNodesWithBOMData()
+    {
+        return [
+            [' '],
+            ["\t"],
+            ["\n"],
+            ["\n\t\n   "],
+        ];
     }
 
     public function testParseIsReentrant()