Allow currently processed/parsed URL to be read from data parser plugin.

Closes #3050274

src/DataParserPluginBase.php

@@ -181,6 +181,15 @@ abstract class DataParserPluginBase extends PluginBase implements DataParserPlug
     return $this->currentItem;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function currentUrl(): ?string {
+    $index = $this->activeUrl ?: \array_key_first($this->urls);
+
+    return $this->urls[$index] ?? NULL;
+  }
+
   /**
    * {@inheritdoc}
    */