Error when materializing files

Hello,

we have a file provider based macOS app. Around June we started receiving reports that our users have problems when opening files. Sometimes they get "Invalid argument" alerts

after double-clicking on a dataless file. We receive similar errors when trying to materialize the files programmatically from our app (not FP extension)(*):

"The operation could not be completed. Invalid argument"
code: 22
domain: "NSPOSIXErrorDomain"
underlyingError: 
    "cannotMaterialize"
     code: 33
     domain: "libfssync.VFSFileError"

We also see those errors with matching timestamps in the output from fileproviderctl dump:

> (...) update-item: 🔶 last:(...) (-1min27s) (...) error:'NSError: POSIX 22 "The operation couldn’t be completed. Invalid argument" Underlying={NSError: libfssync.VFSFileError 33 "cannotMaterialize" }}' domain:none category:<nil> (...)

At the same time our file provider extension receives fetchPartialContents call or no call at all. If it receives the call it finishes with success and returns correct range:

requestedRange: "{0, 15295}"
returnedRange: "{0, 524288}"
alignment: "16384"

Sadly we don't know how to reproduce those issues. We will be grateful for any hints that could be useful in debugging.

Some more context:

• if materializing a file fails with this error, subsequent materialization attempts fail similarly
• in local testing when downloading a file with the code below, or double-click, we only get regular fetchContents call
• file returned by fetchPartialContents should have correct size
• the app is built with XCode 16.1, customers reporting this issue have OS/FP versions: 24F74/2882.120.74 and 24G90/2882.140.30

(*) More or less the code that we use to materialize files

func materializeURL(_ url: URL) throws {
    if try url.isDataless() {
        var error: NSError? = nil
        let coordinator = NSFileCoordinator(filePresenter: nil)

        coordinator.coordinate(readingItemAt: url, error: &error) { _ in }

        if let error {
            throw error
        }
    }
}

private extension URL {
    func isDataless() throws -> Bool {
        let downloadStatus = try self
            .resourceValues(forKeys: [.ubiquitousItemDownloadingStatusKey])
            .ubiquitousItemDownloadingStatus

        return downloadStatus == .notDownloaded || downloadStatus == .none
    }
}