Add slug filter (follow-up to PR #3386)

extra/string-extra/StringExtension.php

@@ -11,16 +11,27 @@
 
 namespace Twig\Extra\String;
 
+use Symfony\Component\String\AbstractUnicodeString;
+use Symfony\Component\String\Slugger\SluggerInterface;
+use Symfony\Component\String\Slugger\AsciiSlugger;
 use Symfony\Component\String\UnicodeString;
 use Twig\Extension\AbstractExtension;
 use Twig\TwigFilter;
 
 final class StringExtension extends AbstractExtension
 {
+    private $slugger;
+
+    public function __construct(SluggerInterface $slugger = null)
+    {
+        $this->slugger = $slugger ?: new AsciiSlugger();
+    }
+    
     public function getFilters()
     {
         return [
             new TwigFilter('u', [$this, 'createUnicodeString']),
+            new TwigFilter('slug', [$this, 'createSlug']),
         ];
     }
 
@@ -28,4 +39,9 @@ final class StringExtension extends AbstractExtension
     {
         return new UnicodeString($text ?? '');
     }
+
+    public function createSlug(string $string, string $separator = '-', ?string $locale = null): AbstractUnicodeString
+    {
+        return $this->slugger->slug($string, $separator, $locale);
+    }
 }