FileProvider fails to trigger re-enumeration

I'm working on a FileProvider which allows access to encrypted files in Dropbox; I can successfully read and present the decrypted files, so I know it's basically working. But I'm having problems getting FileProvider to re-enumerate a folder when its encryption status changes.

When the FileProvider receives an update notification saying a folder is now encrypted, I use signalEnumerator to re-enumerate the folder:

FileProviderExtension.manager?.signalEnumerator(for: existingItem.itemIdentifier, completionHandler: { (ourError : Error?) -> Void in

      if let ourError = ourError {
          log("notifyCallback: mount / unmount failed re-enumeration: \(ourError)")
       } else {
          log("notifyCallback: mount / unmount signalled re-enumeration; pending")
       }
})

The log reports that the re-enumeration is pending... but as far as I can tell, neither enumerateItems nor enumerateChanges is called on the folder's item unless a Finder window is actually open for that folder. This means that, when an app other than Finder tries to access the files through the filesystem, it doesn't see the updated set of filenames.

(For further reference: I've added code to both enumerateItems and enumerateChanges, so that if the call has been triggered by a recent folder-encryption notification, it retrieves a complete set of items from the Dropbox folder. If a retrieved file has an encrypted filename, it reports it as a modified item and returns its filename in-clear; if the filename isn't encrypted, it doesn't return the item (for enumerateItems) or returns it as a deleted item (for enumerateChanges). This approach seems to work successfully for listing folders with a constant state; it's only if the user encrypts / decrypts a folder without currently having a Finder window open inside that folder that I'm not seeing a refresh.)

Any advice on how I can force a re-enumeration without a Finder window currently being displayed?

FileProvider fails to trigger re-enumeration
 
 
Q