If you’re like me, you just spent several days refactoring a framework shared between a host app and its app extension–say, a keyboard extension–into its own project and repository. You finally got everything building again, resolving all the broken framework search paths; then you got everything running again, resolving all the broken bundle paths; but now you’re seeing errors like this when you try to use UserDefaults or the keychain on a device:
2019-01-06 21:29:04.948196-0800 Keyboard[7501:295823] [User Defaults] Couldn't read values in CFPrefsPlistSource<0x163d75700> (Domain: group.com.xxxx.keyboard, User: kCFPreferencesAnyUser, ByHost: Yes, Container: (null), Contents Need Refresh: Yes): Using kCFPreferencesAnyUser with a container is only allowed for System Containers, detaching from cfprefsd 2019-01-06 21:29:04.966103-0800 Keyboard[7501:295823] [User Defaults] Couldn't write value for key test_key in CFPrefsPlistSource<0x163d75b80> (Domain: group.com.xxxx.keyboard, User: kCFPreferencesCurrentUser, ByHost: No, Container: (null), Contents Need Refresh: No): setting preferences outside an application's container requires user-preference-write or file-write-data sandbox access
Weird, right? You googled these errors and found just a couple of things related to sandboxing on macOS, and a bug in a beta iOS release a few years ago. You went down the rabbit hole. You tried adding entitlements to your newly standalone framework. You tried code-signing it. You tried removing and re-creating your App Group.
Then you retraced your footsteps. Started from scratch. And a couple of days into that, you realized that what you didn’t try, after cleaning your entire environment and resetting your device, was turning the keyboard Full Access setting back on.