Show warning if Cryptomator encounters placeholder files in iCloud Drive

[tobihagemann]

Summary

Show warning (e.g., dialog) if Cryptomator encounters placeholder files in iCloud Drive during vault access.

Motivation

Some people encounter empty vaults without any warnings or hints because iCloud Drive optimized the storage:

• https://community.cryptomator.org/t/vault-empty-on-icloud/6314
• https://community.cryptomator.org/t/after-upgrade-to-catilina-and-cryptomator-1-5-3-only-one-file-left-visible-in-vault-and-ios-app-says-no-masterkey/5591
• macOS: iCloud Drive documents missing when offloaded to Optimise Mac Storage  #1530

We already fixed that during migration, see cryptomator/cryptofs#83, but not during vault access.

Considered Alternatives

Ideally, there is some way to transparently "resolve" the placeholder files but I haven't looked into it.

[infeo]

Currently during vault access it is not possible to notify the users, because our underlying library cryptofs does not expose any way to send messages to the gui.

I opened a ticket (see cryptomator/cryptofs#89 ) there, but before we start thinking about that one, maybe there is another way. Maybe the logging can be utilized in a way, that there is a listener to WARN or ERRORS and then show a notification in the GUI.

[infeo]

As an alternative, if we get to know a way to resolved the placeholder files, we can just handle them as conflicts.

[tobihagemann]

This is different to (sync) conflicts and shouldn't be resolved in that way.

Just did some research, you can actually download a placeholder via this shell command:

brctl download <filename>

More info here: https://apple.stackexchange.com/a/387727

But I still don't see a way to transparently access the file. You can retrieve some metadata of the actual file by reading the contents of the placeholder file which is a plist file in binary format (not XML!):

• NSURLNameKey which holds the actual filename.
• NSURLFileSizeKey which holds the actual file size.
• NSURLFileResourceTypeKey which specifies what the actual file type is. For regular files it is NSURLFileResourceTypeRegular.

That's all I could find for now.

[tobihagemann]

It has come to my attention that macOS 15 Sequioa introduced pinning to iCloud Drive via the extended attribute com.apple.fileprovider.pinned.

Based on this, I would suggest a different solution:

Show a warning (e.g., dialog) when Cryptomator unlocks a vault in iCloud Drive that doesn't have the extended attribute com.apple.fileprovider.pinned set.

What do you think, @infeo @overheadhunter?

[infeo]

@tobihagemann A general question, since some time has passed: Is the files-on-demand feature of iCloud still incompatible with Cryptomator?

And what about other file providers? The attribute does not seem iCloud specific.

[tobihagemann]

Oh, you are right. I'm not sure, if this was fixed with macOS 15 Sequoia or earlier. I guess, this issue is obsolete. Thanks for pointing this out!