Add Task Cancellation

[josephearl]

Initial CancellationToken & CancellationTokenSource implementation to match the C# API (system.threading.cancellationtoken and system.threading.cancellationtokensource) and the cancellation API on Android (BoltsFramework/Bolts-Android#53 and BoltsFramework/Bolts-Android#56).

[ghost]

@josephearl This looks amazing!
Sorry for a swarm of comments, but all of these are nits.
Will happily merge this in once all of the nits are resolved.

Keep it up and i am looking really forward to see more of these awesome things!

[dimazen]

Is there any movements on this PR? I'd love to have cancellation support 🌞

[josephearl]

I'll be updating it shortly

[dimazen]

@josephearl thanks!

[josephearl]

Updated. Also added the ability to register a delegate to be notified when a token is cancelled.

[josephearl]

@nlutsenko-fb can you re-run the build please?

No output has been received in the last ... minutes, this potentially indicates a stalled build or something wrong with the build itself.
The build has been terminated

[ghost]

Doing this right now... Thanks!

[ghost]

@josephearl this looks even better!
In addition to nits (I am sorry about them) - I would recommend running a auto-indentation on every new file.

Also - it looks like there is a test failing :(

[josephearl]

• Added copyright
• Formatted new code
• Changed registerDelegate to registerCancellationObserverWithBlock
• Typedef'd BFCancellationBlock

[josephearl]

registration of a delegate

registration of a cancellation observer

[nlutsenko]

Hey @josephearl looks it won't merge automatically (needs rebasing).
Would be awesome to finally have this feature 😋

[josephearl]

Will do

[josephearl]

Rebased and moved logic from CancellationTokenSource to CancellationToken, to match TaskCompletionSource and Task.

[nlutsenko]

@josephearl This looks great! Few comments, but I am very tempted to merge it in...

[josephearl]

Will fix up this evening

[josephearl]

Updated the docs and removed the token getter

[nlutsenko]

This looks great! Merging in!

[emptyway]

Great job! thanks!

I suggest the "Task Cancellation" described in the Readme.md file should be updated with this implementation.

[caoer]

great addition! :)

@nlutsenko @josephearl can I suggestion to make the cancellation token as the third parameter instead of 2nd? It can make the chaining method looks better. not sure how Android or C# doing with it.

change FROM

- (instancetype)continueWithExecutor:(BFExecutor *)executor
                               block:(BFContinuationBlock)block
                   cancellationToken:(BFCancellationToken *)cancellationToken;

TO

- (instancetype)continueWithExecutor:(BFExecutor *)executor
                   cancellationToken:(BFCancellationToken *)cancellationToken;
                               block:(BFContinuationBlock)block

[nlutsenko]

We can do an extra one, since these are already here and we probably don't want to break existing users :(
But a great suggestion, love the trailing block (also it maps waaay better with trailing closures in swift)

[josephearl]

Yes was just about to say we probably don't want to break the API. Sounds like a good addition.

[facebook-github-bot]

@josephearl updated the pull request.