Overwrite an empty field value on node / rendered entity I have a text field in a media image type (for a photo caption) - I'd like to output a default value whenever it's empty.

I tried using HOOK_preprocess_field, but that hook isn't reached if the field of the node is blank.  

It's being inserted in a View, but it's more than one field (a display mode of a Rendered Entity showing a photo thumbnail and the caption) and therefore as the photo is present when the caption isn't, I can't use the No results behaviour.

I also tried HOOK_preprocess_node and HOOK_preproces_content_field, neither of those seem to be called at all in the view.

Is there anywhere else I can edit it?
You might consider overriding an appropriate Twig template, something along the lines of {% if content.field_caption %} {{ content.field_caption }} {% else %}} default text {% endif %}