Extending a base template file such as field.html.twig renders no results?
If you want to only override the field template. 

Try with with the following.


Implement hook_theme like the following no needs for variables and file keys.




  /**
     * Implements hook_theme().
     */
    function myModule_theme($existing, $type, $theme, $path) {
      return [
        'field__parent_task' => [
          'template' => 'field--parent-task',
          'base hook' => 'field',
        ],
      ];
    }




Create templates folder in your module root.  
Create field--parent-task.html.twig inside your templates folder.
Copy and the paste the base template code into your template file.
Clear the cache.