update

templates_user/shop-product/_partial/product-custom-fields.php

@@ -1,11 +1,11 @@
 <? if ( is_array( $this -> custom_fields ) ): foreach ( $this -> custom_fields as $custom_field ):?>
   <div class="custom-field">
     <div class="_name">
-      <?= $custom_field['name'];?>:
+      <?= $custom_field['name'];?><? if ( !empty( $custom_field['is_required'] ) ): ?>*<? endif; ?>:
     </div>
     <div class="_input">
       <div class="grow-wrap">
-        <textarea name="custom_field[<?= $custom_field['id_additional_field'];?>]" field_name="<?= $custom_field['name'];?>" onInput="this.parentNode.dataset.replicatedValue = this.value"></textarea>
+        <textarea name="custom_field[<?= $custom_field['id_additional_field'];?>]" field_name="<?= $custom_field['name'];?>" onInput="this.parentNode.dataset.replicatedValue = this.value" <? if ( !empty( $custom_field['is_required'] ) ): ?>required<? endif; ?>></textarea>
       </div>
     </div>
   </div>

templates_user/shop-product/product.php

@@ -502,7 +502,7 @@
       }
 
       // dodatkowe pola muszą być uzupełnione
-      $( '.custom-field textarea' ).each( function( index, element )
+      $( '.custom-field textarea[required]' ).each( function( index, element )
       {
         if ( $.trim( $( element ).val() ) == '' )
         {