launchdarkly_react_native_client_sdk/LaunchdarklyReactNativeClient.swift:209: Fatal error: Unexpectedly found nil while unwrapping an Optional value

[normtronics]

Is this a support request?
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Describe the bug
When working on my app in the simulator, the SDK crashes my app with a Fatal error: Unexpectedly found nil while unwrapping an Optional value

To reproduce
Just basic use of the app

Expected behavior
The app shouldn't crash

Logs
dyld4 config: DYLD_ROOT_PATH=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot
CoreSimulator 802.6.1 - Device: iPhone 13 (6B1163CA-E62E-4944-924D-A3B08D2D4079) - Runtime: iOS 15.5 (19F70) - DeviceType: iPhone 13
launchdarkly_react_native_client_sdk/LaunchdarklyReactNativeClient.swift:209: Fatal error: Unexpectedly found nil while unwrapping an Optional value
dyld4 config: DYLD_ROOT_PATH=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Library/Developer/CoreSimulator/Profiles/Runtimes/iOS.simruntime/Contents/Resources/RuntimeRoot

SDK version
6.2.1

Language version, developer tools
TypeScript and react

OS/platform
MacOS

Additional context
Add any other context about the problem here.

[louis-launchdarkly]

Hello @normtronics, thank you for reaching out.

I have checked with the https://github.com/launchdarkly/react-native-client-sdk/tree/main/ManualTestApp in the repo, and I was not able to reproduce the crash (I can still launch the app, and the test app can still get flag values from LaunchDarkly).

Would you be able to share your application code, and if possible, the mobile key with us so we can help debug the issue? I recommend you submit a support request (see the links in your issue description) as you do not want to share the mobile key publicly here.

[normtronics]

@louis-launchdarkly Thanks for getting back to me. I'll file a support request as I can't share code here. The crash usually happens in the middle of me using the app for a bit. It doesn't stop the app from launching or getting the flags

[denissb]

Same here after upgrade to version 6.2.0
Exception is thrown here:

 @objc func unregisterFeatureFlagListener(_ flagKey: String, environment: String) {
        let multiListenerId = envConcat(environment: environment, identifier: flagKey)
        if let owner = flagListenerOwners.removeValue(forKey: multiListenerId) {
            LDClient.get(environment: environment)!.stopObserving(owner: owner)
        }

Error:

launchdarkly_react_native_client_sdk/LaunchdarklyReactNativeClient.swift:271: Fatal error: Unexpectedly found nil while unwrapping an Optional value
2022-09-29 02:07:16.173319-0700 golive[20515:121360] launchdarkly_react_native_client_sdk/LaunchdarklyReactNativeClient.swift:271: Fatal error: Unexpectedly found nil while unwrapping an Optional value
(lldb) 

[denissb]

The exception I got was actually related to the feature flags not being accessible, this is due to a recent change in the launch darkly configuration, but I think it is still related to the same root cause - unsafe unwrapping of optionals on iOS.
The SDK still shouldn't crash the application if a feature flag became unavailable, so this is a pretty critical issue in my option.
See below:

[mnikolov-qb]

Hey everyone, I am facing the same issue. From time to time the app crashes on log in with the same 'Unexpectedly found nil while unwrapping an Optional value...' error for flags. We were on 6.2.0, updated to teh latest at this point 6.2.4, but still the same. Does anyone have any solution or workaround for this?

[normtronics]

I have a long running support request to deal with this. They have been looking at it for a bit, so I don't know when or if any changes to their SDK will be made. @denissb I agree, the unsafe unwrapping is not the ideal way to deal with that.

[normtronics]

@mnikolov-qb My team ended up checking if the LD client was nil before we did anything with it. Seems to have fixed the problem for now

[louis-launchdarkly]

Hello @normtronics, thank you for the suggestion - we think that is the issue. On the Android native adapter, there are error checks when the LDClient is null (most commonly happening when the LDClient is still in initialization), but that is not in the iOS code with the force unwrap.

While the team is working on a fix, in the meantime, we recommend checking the LDClient is nil (or waiting for initialization complete) is the correct workaround for now.

[CrispyBacon1999]

We're getting this issue, even when checking ldClient.isInitialized before checking the flags. Any updates on a fix for this?

[johnculviner]

@normtronics could you share some code? We have the same issue and it is causing our app to have a like a 1% crash rate.

[yusinto]

We have released 6.3.1 today which adds nil guards for ldClient which should fix this.

[ruanpotgieter95]

@yusinto tried to update the package version to 6.3.1. Now receiving the following error with the same implementation as before.

Illegal callback invocation from native module. This callback type only permits a single invocation from native code.
When I comment out the jsonVariation it works again. So this is specific to that function.

Not sure why that is happening.

This only seems to happen when running the app on a physical device.

[yusinto]

@ruanpotgieter95 we released 6.3.2 which should fix the illegal callback invocation error.