Is there a way to understand what is causing a crash involving `_NSTouchBarFinderObservation`?

Question

My Crashlytics is showing multiple users experiencing the following crash (see below). The only way I have been able to recreate this (which I doubt the users are doing) is to bring up the Xcode Touch Bar simulator and switch between generations whilst the app is running:

The following devices and OSes have reported the crash:

• macOS 12.2.0 MacBookPro16,1
• macOS 12.2.0 MacBookPro15,4
• macOS 12.1.0 MacBookPro15,4
• macOS 12.0.0 MacBookPro15,4

My app is:

• on macOS only
• written in SwiftUI containing an NSViewController and NSTextView
• never touching/observing/making reference to the touch bar.

Would anyone know the reason for this crash?

---

Cannot remove an observer <_NSTouchBarFinderObservation 0x6000026f6260> for the key path "nextResponder" from <GUL_SwiftUI.AppDelegate-0624A6E4-3CE4-4739-BDD0-0721CE556CBA 0x600000290360> because it is not registered as an observer.
2022-02-13 14:28:47.289790+0400 Lyrcs[63176:1681748] [General] (
    0   CoreFoundation                      0x00000001c1dd41cc __exceptionPreprocess + 240
    1   libobjc.A.dylib                     0x00000001c1b257b8 objc_exception_throw + 60
    2   Foundation                          0x00000001c2c1b96c -[NSObject(NSKeyValueObserverRegistration) _removeObserver:forProperty:] + 668
    3   Foundation                          0x00000001c2c1b67c -[NSObject(NSKeyValueObserverRegistration) removeObserver:forKeyPath:] + 144
    4   Foundation                          0x00000001c2c1b304 -[NSObject(NSKeyValueObserverRegistration) removeObserver:forKeyPath:context:] + 204
    5   AppKit                              0x00000001c4f29df8 -[_NSTouchBarFinderObservation invalidate] + 316
    6   AppKit                              0x00000001c4f2a2ec -[NSTouchBarFinder invalidate] + 268
    7   AppKit                              0x00000001c48ae584 -[NSApplicationFunctionRowController _teardown] + 104
    8   AppKit                              0x00000001c48ae31c -[NSApplicationFunctionRowController _sync] + 484
    9   Foundation                          0x00000001c2bfa13c NSKeyValueNotifyObserver + 292
    10  Foundation                          0x00000001c2cc655c NSKeyValueDidChange + 356
    11  Foundation                          0x00000001c2d79770 NSKeyValueDidChangeWithPerThreadPendingNotifications + 160
    12  AppKit                              0x00000001c5173f80 __33+[NSFunctionRowDevice initialize]_block_invoke.1 + 492
    13  AppKit                              0x00000001c5174324 ___NSMainRunLoopPerformBlockInModes_block_invoke + 44
    14  CoreFoundation                      0x00000001c1d54708 __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 28
    15  CoreFoundation                      0x00000001c1d5457c __CFRunLoopDoBlocks + 412
    16  CoreFoundation                      0x00000001c1d531f4 __CFRunLoopRun + 800
    17  CoreFoundation                      0x00000001c1d52734 CFRunLoopRunSpecific + 600
    18  HIToolbox                           0x00000001ca8e4f68 RunCurrentEventLoopInMode + 292
    19  HIToolbox                           0x00000001ca8e4cdc ReceiveNextEventCommon + 552
    20  HIToolbox                           0x00000001ca8e4a9c _BlockUntilNextEventMatchingListInModeWithFilter + 72
    21  AppKit                              0x00000001c48a8ce0 _DPSNextEvent + 844
    22  AppKit                              0x00000001c48a7584 -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 1332
    23  AppKit                              0x00000001c48995a4 -[NSApplication run] + 596
    24  AppKit                              0x00000001c486ac78 NSApplicationMain + 1064
    25  SwiftUI                             0x00000001e6779c9c $s7SwiftUI6runAppys5NeverOSo21NSApplicationDelegate_So11NSResponderCXcFTf4e_nAA07TestingdG0C_Tg5 + 148
    26  SwiftUI                             0x00000001e72a3a54 $s7SwiftUI6runAppys5NeverOxAA0D0RzlF + 260
    27  SwiftUI                             0x00000001e6d3366c $s7SwiftUI3AppPAAE4mainyyFZ + 128

Answer 1

Turns out the culprit was Firebase Analytics. The solution to prevent this crash was to add the FirebaseAppDelegateProxyEnabled to the info plist and give it a Boolean value of NO. Seems like SwiftUI, macOS and Firebase Analytics don't play nicely together.