Prepare options before prepopulate

Could we check that $element['#options'] is empty before calling $element_plugin->prepare($element);?

We could, but should not prepare() be called unconditionally in this layer as well?

Bump! :)

I spent a few minute digging into this and the answer to

I used the prepare() method (what else I should have used for this?) to prepopulate the #options element key from the external storage.

...is to use the \Drupal\webform\Plugin\WebformElementBase::initialize method.

Do this fix your custom elements external options population?