tracesSampler becomes NSNull in iOS and the app cannot be started

[kitoko552]

Environment

How do you use Sentry?
Sentry SaaS (sentry.io)

Which SDK and version?
"@sentry/react-native": "^3.1.1"

Steps to Reproduce

1. Sentry.init with tracesSampler and enable the automatic instrumentation of performance monitoring.

Sentry.init({
  dsn: Config.sentry.dns,
  tracesSampler: samplingContext => {
    return 0.2
  },
  integrations: [
    new Sentry.ReactNativeTracing({
      routingInstrumentation,
      enableAppStartTracking: false,
    }),
  ],
})

const navigationRef = createNavigationContainerRef()
const RootContents = React.memo(() => {
  return (
    <NavigationContainer
      ref={navigationRef}
      onReady={() => {
        routingInstrumentation.registerNavigationContainer(navigationRef)
      }}
      onStateChange={async state => {
        ...
      }}
    >
      ...
    </NavigationContainer>
  )
})
...
export default Sentry.wrap(Root) // Root uses RootContents

2. Build the app on iOS

3. The app crashes at here because _options.tracesSampler is NSNull

Expected Result

No Crashing and the app can be started correctly.

Actual Result

The stack trace is here.

  * thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=2, address=0x1e3dfa8e8)
    frame #0: 0x00000001e3dfa8e8 CoreFoundation`__kCFNull
  * frame #1: 0x0000000101b62134 {our_app_name}`-[SentryTracesSampler sample:](self=0x000000028187f9e0, _cmd="sample:", context=0x0000000281f03c00) at SentryTracesSampler.m:34:38
    frame #2: 0x0000000101b3ce14 {our_app_name}`-[SentryHub startTransactionWithContext:bindToScope:waitForChildren:customSamplingContext:](self=0x0000000283c7d630, _cmd="startTransactionWithContext:bindToScope:waitForChildren:customSamplingContext:", transactionContext=0x0000000283b24e40, bindToScope=YES, waitForChildren=YES, customSamplingContext=0 key/value pairs) at SentryHub.m:312:34
    frame #3: 0x0000000101b49cac {our_app_name}`-[SentryPerformanceTracker startSpanWithName:operation:](self=0x0000000281f038e0, _cmd="startSpanWithName:operation:", name=@"RNScreensViewController", operation=@"ui.load") at SentryPerformanceTracker.m:56:13
    frame #4: 0x0000000101b64e0c {our_app_name}`-[SentryUIViewControllerPerformanceTracker createTransaction:](self=0x0000000281d24b50, _cmd="createTransaction:", controller=0x0000000141215df0) at SentryUIViewControllerPerformanceTracker.m:78:18
    frame #5: 0x0000000101b64d34 {our_app_name}`__87-[SentryUIViewControllerPerformanceTracker viewControllerViewDidLoad:callbackToOrigin:]_block_invoke(.block_descriptor=0x000000016f33fb88) at SentryUIViewControllerPerformanceTracker.m:61:24
    frame #6: 0x0000000101b66008 {our_app_name}`-[SentryUIViewControllerPerformanceTracker limitOverride:target:callbackToOrigin:block:](self=0x0000000281d24b50, _cmd="limitOverride:target:callbackToOrigin:block:", description=@"viewDidLoad", viewController=0x0000000141215df0, callbackToOrigin=0x0000000101b676cc, block=0x0000000101b64d04) at SentryUIViewControllerPerformanceTracker.m:288:9
    frame #7: 0x0000000101b64cbc {our_app_name}`-[SentryUIViewControllerPerformanceTracker viewControllerViewDidLoad:callbackToOrigin:](self=0x0000000281d24b50, _cmd="viewControllerViewDidLoad:callbackToOrigin:", controller=0x0000000141215df0, callbackToOrigin=0x0000000101b676cc) at SentryUIViewControllerPerformanceTracker.m:57:5
    frame #8: 0x0000000101b676a8 {our_app_name}`__55-[SentryUIViewControllerSwizziling swizzleViewDidLoad:]_block_invoke_2(.block_descriptor=0x0000000281191080, self=0x0000000141215df0) at SentryUIViewControllerSwizziling.m:207:5
    frame #9: 0x000000019345f3a4 UIKitCore`-[UIViewController _sendViewDidLoadWithAppearanceProxyObjectTaggingEnabled] + 104
    frame #10: 0x000000019346395c UIKitCore`-[UIViewController loadViewIfRequired] + 928
    frame #11: 0x0000000193463d3c UIKitCore`-[UIViewController view] + 28
    frame #12: 0x000000010175cd70 {our_app_name}`-[RNSScreenContainerView setupController](self=0x00000001412139f0, _cmd="setupController") at RNSScreenContainer.m:60:32
    frame #13: 0x000000010175cca4 {our_app_name}`-[RNSScreenContainerView init](self=0x00000001412139f0, _cmd="init") at RNSScreenContainer.m:51:5
    frame #14: 0x000000010175e400 {our_app_name}`-[RNSScreenContainerManager view](self=0x0000000281d360c0, _cmd="view") at RNSScreenContainer.m:241:10
    frame #15: 0x0000000101790568 {our_app_name}`-[RCTComponentData createViewWithTag:rootTag:](self=0x0000000283c62080, _cmd="createViewWithTag:rootTag:", tag=0x948ae92eb8cd1839, rootTag=0x948ae92eb8cd0d39) at RCTComponentData.m:70:18
    frame #16: 0x0000000101880884 {our_app_name}`__50-[RCTUIManager createView:viewName:rootTag:props:]_block_invoke(.block_descriptor=0x0000000283c7f750) at RCTUIManager.m:998:30
    frame #17: 0x0000000101889f30 {our_app_name}`__RCTExecuteOnMainQueue_block_invoke(.block_descriptor=0x000000028118f5a0) at RCTUtils.m:261:7
    frame #18: 0x000000011068fae8 libdispatch.dylib`_dispatch_call_block_and_release + 24
    frame #19: 0x000000011069132c libdispatch.dylib`_dispatch_client_callout + 16
    frame #20: 0x000000011069f76c libdispatch.dylib`_dispatch_main_queue_callback_4CF + 972
    frame #21: 0x0000000191202998 CoreFoundation`__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 12
    frame #22: 0x00000001911fcdf8 CoreFoundation`__CFRunLoopRun + 2528
    frame #23: 0x00000001911fbed0 CoreFoundation`CFRunLoopRunSpecific + 572
    frame #24: 0x0000000192459e64 Foundation`-[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 228
    frame #25: 0x0000000192459d44 Foundation`-[NSRunLoop(NSRunLoop) runUntilDate:] + 88
    frame #26: 0x0000000101d2e6b8 {our_app_name}`+[RNSplashScreen show](self=RNSplashScreen, _cmd="show") at RNSplashScreen.m:31:9
    frame #27: 0x0000000100ac410c {our_app_name}`-[AppDelegate application:didFinishLaunchingWithOptions:](self=0x0000000281f6e940, _cmd="application:didFinishLaunchingWithOptions:", application=0x000000013ff05c60, launchOptions=0x0000000000000000) at AppDelegate.m:61:3
    frame #28: 0x0000000193b257b0 UIKitCore`-[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 356
    frame #29: 0x0000000193b27150 UIKitCore`-[UIApplication _callInitializationDelegatesWithActions:forCanvas:payload:fromOriginatingProcess:] + 3432
    frame #30: 0x0000000193b2cf24 UIKitCore`-[UIApplication _runWithMainScene:transitionContext:completion:] + 1244
    frame #31: 0x00000001931ff8c0 UIKitCore`-[_UISceneLifecycleMultiplexer completeApplicationLaunchWithFBSScene:transitionContext:] + 148
    frame #32: 0x00000001937242c8 UIKitCore`_UIScenePerformActionsWithLifecycleActionMask + 96
    frame #33: 0x00000001932003a8 UIKitCore`__101-[_UISceneLifecycleMultiplexer _evalTransitionToSettings:fromSettings:forceExit:withTransitionStore:]_block_invoke + 196
    frame #34: 0x00000001931ffeb0 UIKitCore`-[_UISceneLifecycleMultiplexer _performBlock:withApplicationOfDeactivationReasons:fromReasons:] + 472
    frame #35: 0x00000001932001d4 UIKitCore`-[_UISceneLifecycleMultiplexer _evalTransitionToSettings:fromSettings:forceExit:withTransitionStore:] + 740
    frame #36: 0x00000001931ffa90 UIKitCore`-[_UISceneLifecycleMultiplexer uiScene:transitionedFromState:withTransitionContext:] + 336
    frame #37: 0x000000019320772c UIKitCore`__186-[_UIWindowSceneFBSSceneTransitionContextDrivenLifecycleSettingsDiffAction _performActionsForUIScene:withUpdatedFBSScene:settingsDiff:fromSettings:transitionContext:lifecycleActionType:]_block_invoke + 188
    frame #38: 0x000000019363e38c UIKitCore`+[BSAnimationSettings(UIKit) tryAnimatingWithSettings:actions:completion:] + 812
    frame #39: 0x000000019373c184 UIKitCore`_UISceneSettingsDiffActionPerformChangesWithTransitionContext + 248
    frame #40: 0x0000000193207420 UIKitCore`-[_UIWindowSceneFBSSceneTransitionContextDrivenLifecycleSettingsDiffAction _performActionsForUIScene:withUpdatedFBSScene:settingsDiff:fromSettings:transitionContext:lifecycleActionType:] + 356
    frame #41: 0x0000000193046ae4 UIKitCore`__64-[UIScene scene:didUpdateWithDiff:transitionContext:completion:]_block_invoke + 772
    frame #42: 0x0000000193045590 UIKitCore`-[UIScene _emitSceneSettingsUpdateResponseForCompletion:afterSceneUpdateWork:] + 248
    frame #43: 0x0000000193046730 UIKitCore`-[UIScene scene:didUpdateWithDiff:transitionContext:completion:] + 220
    frame #44: 0x0000000193b2b0fc UIKitCore`-[UIApplication workspace:didCreateScene:withTransitionContext:completion:] + 548
    frame #45: 0x0000000193664a84 UIKitCore`-[UIApplicationSceneClientAgent scene:didInitializeWithEvent:completion:] + 360
    frame #46: 0x000000019fd65d00 FrontBoardServices`-[FBSScene _callOutQueue_agent_didCreateWithTransitionContext:completion:] + 412
    frame #47: 0x000000019fd8d4fc FrontBoardServices`__94-[FBSWorkspaceScenesClient createWithSceneID:groupID:parameters:transitionContext:completion:]_block_invoke.176 + 100
    frame #48: 0x000000019fd73420 FrontBoardServices`-[FBSWorkspace _calloutQueue_executeCalloutFromSource:withBlock:] + 232
    frame #49: 0x000000019fd8d214 FrontBoardServices`__94-[FBSWorkspaceScenesClient createWithSceneID:groupID:parameters:transitionContext:completion:]_block_invoke + 312
    frame #50: 0x000000011069132c libdispatch.dylib`_dispatch_client_callout + 16
    frame #51: 0x00000001106947e4 libdispatch.dylib`_dispatch_block_invoke_direct + 232
    frame #52: 0x000000019fdb1e04 FrontBoardServices`__FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 40
    frame #53: 0x000000019fdb1acc FrontBoardServices`-[FBSSerialQueue _targetQueue_performNextIfPossible] + 404
    frame #54: 0x000000019fdb1fa0 FrontBoardServices`-[FBSSerialQueue _performNextFromRunLoopSource] + 28
    frame #55: 0x0000000191202fa8 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24
    frame #56: 0x0000000191202ea8 CoreFoundation`__CFRunLoopDoSource0 + 204
    frame #57: 0x00000001912021fc CoreFoundation`__CFRunLoopDoSources0 + 256
    frame #58: 0x00000001911fc718 CoreFoundation`__CFRunLoopRun + 768
    frame #59: 0x00000001911fbed0 CoreFoundation`CFRunLoopRunSpecific + 572
    frame #60: 0x00000001a7945570 GraphicsServices`GSEventRunModal + 160
    frame #61: 0x0000000193b292d0 UIKitCore`-[UIApplication _run] + 1052
    frame #62: 0x0000000193b2e84c UIKitCore`UIApplicationMain + 164
    frame #63: 0x0000000100ac4980 {our_app_name}`main(argc=1, argv=0x000000016f343730) at main.m:7:12
    frame #64: 0x0000000190eda140 libdyld.dylib`start + 4

Maybe the function type like tracesSampler can't be passed from React Native to the iOS module.

[marandaneto]

@kitoko552 thanks for reporting, I've raised this issue on the Cocoa SDK getsentry/sentry-cocoa#1441

for now, a workaround is to avoid tracesSampler and instead use the tracesSampleRate, sorry about that.