Add additional field formatters

Hello, thank you for the submission.

Such a new feature needs full test coverage.

Also even such a simple implementation adds maintenance complexity. We need a real world usecase explained where this functionality is used.

The most common use case „Paragraphs“ does not apply here as it doesn‘t have a label.

I think need improvement here.
In some cases we have entity_reference_revisions field, but we need to show link (and label as well) to the current entity revision.
This patch add this capability. It's based on the patch from comment #31.

So label formatter now have "Ignore referenced revision" setting. If it's set to true - the formatter will show label/link to the current entity revision (instead of actually linked).

Also the patch adds overridden EntityReferenceRevisionsFormatterBase::getEntitiesToView() which can be used to get the same behavior for other for other formatters.

I am just putting this here for anyone who comes here looking for a quick fix to get field formatters for entity_reference_revisions.
I implement the standard entity reference formatters on entity reference revisions with this simple function in a module:

/**
 * Apply entity_reference formatters to entity_reference_revisions.
 * @param array $info
 */
function MYMODULE_field_formatter_info_alter(array &$info) {
  foreach($info as &$field) {
    if(in_array('entity_reference', $field['field_types'])) {
      $field['field_types'][] = 'entity_reference_revisions';
    }
  }
  // Remove reference.
  unset($field);
}

Though, this wont take the revision into account when outputting the field (I don't think).

Maybe this could be implemented into the module and then formatters specific to this module could be implemented which just extend the entity_reference formatters and override which entity is loaded.

Just a thought and I haven't really looked into it.

Updated patch 31.

Configuration for formatter has been added, fixed Drupal coding standards, renamed deprecated functions. Test has been rewritten - composite entities (like paragraph) don't have own pages, so no need to add routes to them.

Fix test for D9.

Reviewed and tested, moving it to RTBC.

Merged, thanks.

The ID formatter also has multiple real world use cases although it does not make much sense for Paragraphs. In my case, I have a reference field using the ERR and I want to use the ID in views re-write results while in another scenario I'm trying to embed another view with the help of Views Field View and passing the ID value as a contextual filter.