Fix: Empty lines in code blocks

app/Services/Markdown/Formatter.php

@@ -3,6 +3,7 @@
 namespace App\Services\Markdown;
 
 use App\Services\Markdown\Renderers\LinkRenderer;
+use DOMDocument;
 use Illuminate\Support\Facades\Blade;
 use Illuminate\Support\Facades\Cache;
 use League\CommonMark\Environment\Environment;
@@ -58,6 +59,7 @@ public function render(): string
 
         // Perform final adjustments like inserting non-breaking spaces
         $result = $this->insertNonBreakingSpaces($converted->getContent());
+        $result = $this->removeEmptyCodeLines($result);
 
         // Cache::put($cacheKey, $result, now()->addMonth());
 
@@ -122,4 +124,32 @@ protected function insertNonBreakingSpaces(string $html): string
         // Perform the replacements and return the modified HTML
         return preg_replace($patterns, $replacements, $html);
     }
+
+    /**
+     * For some reason, to date (04-2024), HighlightCodeExtension appends empty
+     * lines at the end of a code block. We need to get rid of them.
+     */
+    protected function removeEmptyCodeLines(string $html): string
+    {
+        $body = mb_convert_encoding($html, 'HTML-ENTITIES', 'UTF-8');
+
+        libxml_use_internal_errors(true);
+
+        $dom = new DOMDocument('1.0', 'UTF-8');
+
+        $dom->loadHtml($body);
+
+        libxml_clear_errors();
+
+        $xpath = new \DOMXPath($dom);
+        $spans = $xpath->query('//pre/code/span[@class="line" and not(node())]');
+
+        foreach ($spans as $span) {
+            if ($span->isSameNode($span->parentNode->lastChild)) {
+                $span->parentNode->removeChild($span);
+            }
+        }
+
+        return $dom->saveHTML();
+    }
 }