Issue #3222697 by nmangold: Use mb_substr() instead of mb_strlen() in makeUnique()

composer.json

@@ -4,5 +4,7 @@
   "type": "drupal-module",
   "license": "GPL-2.0+",
   "minimum-stability": "dev",
-  "require": { }
+  "require": {
+    "ext-mbstring": "*"
+  }
 }

src/Plugin/CommerceAutoSkuGenerator/CommerceAutoSkuGeneratorBase.php

@@ -58,7 +58,7 @@ abstract class CommerceAutoSkuGeneratorBase extends PluginBase  implements Comme
     while (!$this->isUnique($entity, $output)) {
       $counter_length = mb_strlen($i) + 1;
       $un_prefixed_max_length = 255 - $counter_length;
-      $sku = mb_strlen($generated_sku, 0, $un_prefixed_max_length);
+      $sku = mb_substr($generated_sku, 0, $un_prefixed_max_length);
       $output = $sku . '_' . $i;
       $i++;
     };