allow vendord

vendor/league/commonmark/src/Parser/Block/SkipLinesStartingWithLettersParser.php

@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the league/commonmark package.
+ *
+ * (c) Colin O'Dell <colinodell@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace League\CommonMark\Parser\Block;
+
+use League\CommonMark\Parser\Cursor;
+use League\CommonMark\Parser\MarkdownParserStateInterface;
+use League\CommonMark\Util\RegexHelper;
+
+/**
+ * @internal
+ *
+ * This "parser" is actually a performance optimization.
+ *
+ * Most lines in a typical Markdown document probably won't match a block start. This is especially true for lines starting
+ * with letters - nothing in the core CommonMark spec or our supported extensions will match those lines as blocks. Therefore,
+ * if we can identify those lines and skip block start parsing, we can optimize performance by ~10%.
+ *
+ * Previously this optimization was hard-coded in the MarkdownParser but did not allow users to override this behavior.
+ * By implementing this optimization as a block parser instead, users wanting custom blocks starting with letters
+ * can instead register their block parser with a higher priority to ensure their parser is always called first.
+ */
+final class SkipLinesStartingWithLettersParser implements BlockStartParserInterface
+{
+    public function tryStart(Cursor $cursor, MarkdownParserStateInterface $parserState): ?BlockStart
+    {
+        if (! $cursor->isIndented() && RegexHelper::isLetter($cursor->getNextNonSpaceCharacter())) {
+            $cursor->advanceToNextNonSpaceOrTab();
+
+            return BlockStart::abort();
+        }
+
+        return BlockStart::none();
+    }
+}