Apparent dealloc error after Swift 5/Xcode 10.3 upgrade about brightfutures

[phimage]

did you have a strong reference on the Future returned by handleRequest?

[Thomvis]

Sorry to hear you're encountering issues. I can't reproduce the issue myself, it would be helpful if you could provide a crashing test case in a PR if possible.

Could you also try rewriting the method to not use a Promise (as shown at https://github.com/Thomvis/BrightFutures#providing-futures) to see if the crash still happens?

[adjustnox]

I removed all Promises (there were several, nested). Once I switched to using only futures, the crashes stopped.

[Thomvis]

Glad to hear. Would still love to have a reproducing test case to get this issue fixed, so if you have any insights you can share please do :)

[adjustnox]

I have a project I am working on to do just that. Will post back when I get it in place.

[marchy]

We're getting this exact same issue happening after the Swift 5/Xcode 11/BrightFutures 8.0.0 upgrade.

@adjustnox any luck on getting the reproducible project set up?

@Thomvis We tried converting the following block to Futures:

{
	private var computeFeedItemsTask:Future<[ContentItemVM], Never>?



	// FAILING METHOD
	private func computeFeedItems() -> Future<[ContentItemVM], Never> {
		...

		let existingComputation:Future<[ContentItemVM], Never> = computeFeedItemsTask ?? Future( value: [ContentItemVM]() )
		// FAILING LINE
		let existingComputationPart:String = (existingComputation.isCompleted) ? "finished" : "in progress...."

		...

		computeFeedItemsTask = existingComputation.map( computeFeedItemsQueue.context ){ _ /*(_:[FeedItemVM])*/ -> /*Future<*/[ContentItemVM]/*, NoError>*/ in
			...

			return feedItems

		}.onSuccess( DispatchQueue.main.context ){ (feedItems:[ContentItemVM]) in
			...
		}
	}
}

STACK TRACE:

#0	0x0000000112ebf94f in swift_getAssociatedTypeWitnessSlowImpl(swift::MetadataRequest, swift::TargetWitnessTable<swift::InProcess>*, swift::TargetMetadata<swift::InProcess> const*, swift::TargetProtocolRequirement<swift::InProcess> const*, swift::TargetProtocolRequirement<swift::InProcess> const*) ()

#2	0x000000010ee8edaf in AsyncType.isCompleted.getter ()

#3	0x000000010eb491f6 in FeedController.computeFeedItems() at /Users/marchy/Documents/Projects/Happ/Mobile-iOS/Code/Happ.Mobile/Controllers/FeedController.swift:2090

#4	0x000000010eb2c8f5 in FeedController.viewDidLoad() at /Users/marchy/Documents/Projects/Happ/Mobile-iOS/Code/Happ.Mobile/Controllers/FeedController.swift:936

by changing the .map{...} call above to computeFeedItemsTask = Future { complete in DispatchQueue.global().async { ... }} as suggested in the docs, but it actually doesn't even run that far, since existingComputation fails beforehand when trying to access existingComputation.isCompleted when set with its initial empty array value (Future( value: [ContentItemVM]() )).

Here's some outputs of the Future's state:

(lldb) po existingComputation
Async<Result<Array<ContentItemVM>, Never>>(Optional(Swift.Result<Swift.Array<Happ_Mobile.ContentItemVM>, Swift.Never>.success([])))

(lldb) po existingComputation.isCompleted
error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=1, address=0x0).

(lldb) po existingComputation.result
▿ Optional<Result<Array<ContentItemVM>, Never>>
  ▿ some : Result<Array<ContentItemVM>, Never>
    - success : 0 elements

Seems pretty wild given the implementation of AsyncType::isCompleted seems to be simply:

public extension AsyncType {
    var isCompleted: Bool {
        return result != nil
    }
    ...
}

[marchy]

Hi @Thomvis @adjustnox did you guys have a chance to look into this by any chance?

This is preventing us from upgrading to Xcode 11 / Swift 5 / iOS 13.
Any insight would be much appreciated

[adjustnox]

It was a hold up for us as well, so we ended up replacing the promises with escaping closures :/

Can't offer any help, I'm afraid.

[Thomvis]

Sorry that this is still an issue. Still not sure what the root cause could be and why this is not reproducible in a new/simple project.

Can you think of any way in which your projects are similarly special? E.g. what is the install method (CocoaPods, Carthage, etc.)

[adjustnox]

Cocoapods for us.

I can say we had several nested promises, which we switched to futures as per earlier suggestions.