TypeError: Argument 1 passed to Drupal\default_content\Normalizer\ContentEntityNormalizer::addDependency() must implement interface Drupal\Core\Entity\ContentEntityInterface, null given

Yes, not clear which entity does not implement this interface and why it's serialized

If there's reason to process broader types there's FieldableEntityInterface which can be used as the argument type for \Drupal\default_content\Normalizer\ContentEntityNormalizer::addDependency()

The method using only 2 methods of EntityInterface so here's a patch

Sometimes exporting of entities resulted in the following error:

TypeError: Drupal\default_content\Normalizer\ContentEntityNormalizer::addDependency(): Argument #1 ($entity) must be of type Drupal\Core\Entity\EntityInterface, null given, called in /app/modules/contrib/default_content/src/Normalizer/ContentEntityNormalizer.php on line 453 in /app/modules/contrib/default_content/src/Normalizer/ContentEntityNormalizer.php on line 482 #0 /app/modules/contrib/default_content/src/Normalizer/ContentEntityNormalizer.php(453): Drupal\default_content\Normalizer\ContentEntityNormalizer->addDependency(NULL)

so I rerolled the latest patch and added a double check to assert that the argument being sent to addDependency() function is always an EntityInterface

Merge request wasn't updated with recent patches, and I disagree with the API change to EntityInterface. default_content is about content entities. There's no need to expand that.

Thank you @berdir for your comment. I have updated MR!7 with the changes from patch #11 while still keeping the ContentEntityInterface requirement.

Thanks, one more review.