Why is url.bookmarkData returning nil?

Question

We have an implementation with the UIDocumentPickerViewController that looks something like this:

case .openInitialization:
    // Setup UIDocumentPicker.
    if #available(iOS 14, *) {
        documentsPicker = UIDocumentPickerViewController(forOpeningContentTypes: [
            UTType.text,
            UTType.utf8PlainText,
            UTType.flatRTFD,
            UTType.pdf])
    } else {
        documentsPicker = UIDocumentPickerViewController(documentTypes: [
            String(kUTTypeText),
            String(kUTTypeUTF8PlainText),
            String(kUTTypeFlatRTFD),
            String(kUTTypePDF)], in: .open)
    }

Everything works great and we can select a document. When we select a document we get a document url but in some cases (especially with one drive) we get issues when we want to turn the url into a bookmark. Following code returns nil:

guard let bookmark = try? url.bookmarkData(options: .minimalBookmark, includingResourceValuesForKeys: nil, relativeTo: nil) else { return }

Do anyone have an idea to why this is happening? Or what we can do to get it to work without returning nil?

Edit:

We've tryed to add try catch and we got following error which doesn't quite help much: Error Domain=NSCocoaErrorDomain Code=260 (file doesn't exist).

Edit 2:

So if I open from archive directly into our app it works no issues at all. But we still need to work from UIDocumentPickerViewController.

Also for some reasons files unlocked this way will just work from UIDocumentPickerViewController afterward.

Files can also be opened from onedrive and from there be opened in another app (ours). But this does't and gives a file does not exist error as well.

Edit 3: So I've tested and read a ton. I can tell that following will return false for some files picked by documentpicker:

var exist = FileManager.default.fileExists(atPath: url.path)

But again if I open the file just once from iOS archive app it will work perfectly fine afterward. If there just were some way to tell it to update/download like apples does.

Edit 4: I've made a sample project demonstrating the problem at github .

Answer 1

I answered a similar question here: PDFKit doesn’t work on iPads while works fine on a simulator [iOS, Swift]

Can you check if wrapping your url in a security access scope helps?:

url.startAccessingSecurityScopedResource()
print(FileManager.default.fileExists(atPath: url.path))
url.stopAccessingSecurityScopedResource()

The above should print true. This is because these API's access files outside of the applications sandbox.

See: https://developer.apple.com/documentation/uikit/view_controllers/providing_access_to_directories

Answer 2

Used a technical ticket for apple and they came with a solution :D

NSFileCoordinator().coordinate(readingItemAt: url, options: .withoutChanges, error:&err, byAccessor: { (newURL: URL) -> Void in
  do {
    let bookmark = try newURL.bookmarkData()
  } catch let error {
    print("\(error)")
  }
})

if let err = err {
  print(err.localizedDescription)
}