Order of field settings is not always the same

My team and I ran against something very odd regarding the exported configuration files of dynamic entity reference fields.

Saving the field settings form on my computer resulted in the following config export:

...
settings:
  ...
  comment_type:
    handler: 'default:comment_type'
    handler_settings: {  }
  comment:
    handler: 'default:comment'
    handler_settings: {  }
  ...
...

When my colleagues saved the same form on their computer, their config export resulted in the following:

...
settings:
  ...
  comment:
    handler: 'default:comment'
    handler_settings: {  }
  comment_type:
    handler: 'default:comment_type'
    handler_settings: {  }
  ...
...

As you can see, the ordering between comment and comment_type is different.

I decided to dig into this a little deeper and it appears \Drupal\dynamic_entity_reference\Plugin\Field\FieldType\DynamicEntityReferenceItem::defaultFieldSettings() is responsible for making sure all the entity types are added to the settings array. It basically retrieves all the entity types using \Drupal::service('entity_type.repository')->getEntityTypeLabels(), which on its turn uses \Drupal::entityTypeManager()->getDefinitions().

Entity types (at least the ones that are not dynamically added) are plugins that live in their own file (for example core/modules/comment/src/Entity/Comment.php or web/core/modules/node/src/Entity/Node.php). These files are retrieved using the \RecursiveDirectoryIterator class, which extends the \FilesystemIterator class. These iterators do not enforce any sorting in their return value - they basically return files in the same order the filesystem gave them to it. See, for example, https://www.php.net/manual/en/class.recursivedirectoryiterator.php#120971 or https://stackoverflow.com/questions/29102983/order-in-filesystemiterator....

Because the order of files (and thus entity type definitions) can vary based on your filesystem, the exported config can differ. To prevent this from happening I would like to propose to store the settings in alphabetical order. This way the order of settings is consistent across all possible file systems.