Usage check prevents media being deleted due to thumbnail

On this site there are multiple ways of adding images. Images which come from an external integration (via a custom entity browser) only have 1 usage, whereas images added with the Drupal file upload have 2.

I suspect it might be this thumbnail in the image upload field which creates the extra usage:

This is using the "Image (focal point)" widget from the focal_point module, but I changed it to the core "Image" widget and it still gets 2 usages - it still creates a thumbnail to the left of the filename after uploading.

The frustrating thing is there is no way to tell where a file is used - it's just a scalar count, without any information about where the usage is.

So I have no way to tell whether a file is in use or not. The thumbnail on the image upload page is not a real use! Is this a core bug?

This function Media::loadThumbnail() adds the target_id of the file into the thumbnail field, and then the postSave() on the field will add a usage. I can't see any way to prevent this from happening.

I've been barking up completely the wrong tree. All of the above is a red herring. The fact it has 2 usages in the file_usage table is not what the media_file_delete module uses to determine it. Those usages actually get reduced down by CoreFileUsageResolver::getFileUsages():

public function getFileUsages(FileInterface $file) : int {
  return array_reduce($this->fileUsage->listUsage($file), function (int $count, array $module_usage) {
    return $count + array_reduce($module_usage, function (int $object_count, array $object_usage) {
        return $object_count + count($object_usage);
    }, 0);
  }, 0);
}

The reason there are 2 usages is because media_file_delete combines the file usage with the entity usage in ChainedFileUsageResolver::getFileUsages():

public function getFileUsages(FileInterface $file): int {
  $usage = 0;
  foreach ($this->getSortedResolvers() as $resolver) {
    assert($resolver instanceof FileUsageResolverInterface);
    $usage += $resolver->getFileUsages($file);
  }
  return $usage;
}

So I am not sure whether this is a bug or not. I still think the module doesn't do what it's supposed to out of the box if you combine it with entity_usage, but I'm not sure how to fix that or if it should be. I suppose it needs to realise if one of the usages is the media entity that the file usage is also on, then that's the same usage and it's safe to delete.

Logically, I think we can always subtract 1 from the usage if the media_file_delete_entity_usage is enabled. You can assume 1 usage will always be from the file itself, so the usages on the media entity are all that's relevant. This can be checked in MediaDeleteForm.php.

I've rewritten the issue description with the actual problem.

Here is my proposed solution which I think should work for all scenarios. It excludes the media entity which is trying to be deleted from the count, because by definition we don't care about that usage if that's the thing we want to delete.

This should work even if the media_file_delete_entity_usage module is not enabled.

I'm experiencing a similar issue in D-10.4.8, and patch #9 doesn't seem to resolve the issue. I have both 'Media File Delete' and 'Media File Delete - Entity Usage' enabled. I'm not sure if this helps, but the problem may be more of a cache issue. At deletion, the file isn't deleted because it recognizes itself. After deleting the media item, I immediately check in Files and it still shows a usage. Then I clear cache and the usage becomes 0.