Support Media Library Media Modify reference fields

imclean → changed the visibility of the branch 3422506-support-media-library-modify to hidden.

This works fine as a normal field formatter.

Using Field block → the target_bundles is missing (and possibly other field config settings).

I can't tell which of the 3 modules is responsible.

Fieldblock might be the problem. In its file src/Plugin/Block/FieldBlock.php there's a comment for getFieldDefinition():

   * A FieldBlock works on an entity type across bundles, and thus only has
   * access to field storage definitions. In order to be able to use formatters,
   * we create a generic field definition out of that storage definition.

I think both the entity type and bundle are required to get additional config settings via entityFieldManager->getFieldDefinitions().

The fieldblock issue in #7 also adds support for third party settings which is used by Photoswipe Dynamic Caption.

If you want to modify photoswipe formatter then you locked by #3301760.

I really dislike adding contrib module specific code. Any better approaches?

I was following the existing pattern but yeah, I tend to agree.

It might be better to rewrite it to check for Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem using is_a() or similar. Or if it implements Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItemInterface. But this might be tricky to do in annotations.