Completion invoked twice

[macdrevx]

We wrap LDClient.start in withCheckedContinuation and we have a crash stemming from the continuation being invoked twice. Looking at the implementation, I'm pretty sure there's a race condition here that permits the completion block to be invoked more than once:

ios-client-sdk/LaunchDarkly/LaunchDarkly/LDClient.swift

Lines 836 to 849 in cb270ec

	let startTime = Date().timeIntervalSince1970
	start(serviceFactory: serviceFactory, config: config, context: context) {
	internalCompletedQueue.async {
	if startTime + startWaitSeconds > Date().timeIntervalSince1970 && completed {
	completed = false
	completion?(completed)
	}
	}
	}
	internalCompletedQueue.asyncAfter(deadline: .now() + startWaitSeconds) {
	if completed {
	completion?(completed)
	}
	}

[macdrevx]

It seems like the assumption here is that the closure passed to internalCompletedQueue.async on line 838 will always be invoked before the closure passed to internalCompletedQueue.asyncAfter(deadline:) on line 845.

However, if (1) the closure passed to internalCompletedQueue.asyncAfter(deadline:) runs first and (2) the closure passed to internalCompletedQueue.async runs while startTime + startWaitSeconds > Date().timeIntervalSince1970 is still true, then the completion closure will be invoked twice.

In our case, we're passing 10 for startWaitSeconds.

[tanderson-ld]

Thank you @macdrevx, taking a look.

[tanderson-ld]

We have merged a fix in #429 and will be releasing that shortly. Thank you again for investigating and helping us hone in on that spot of code. Which version of the SDK are you using?

[macdrevx]

Thanks! We're on 9.12.0

[macdrevx]

Also, I left a small suggestion on that pr: https://github.com/launchdarkly/ios-client-sdk/pull/429/files#r1953291290

[tanderson-ld]

Your suggestions are absolutely valid. I thought about that while making the tweak, but wanted to minimize impact risk. I'll keep those in mind if I touch that code in the future.

9.12.3 was released with the fix and should be propagating through the package distribution systems.