I must admit that I do like this approach, however I'm not too familiar with the proposed spec to definitively comment on this. Have you tried proposing this in the https://github.com/tc39/proposal-cancelable-promises repository? That may be a better avenue for your suggestions.
On Sat, Oct 15, 2016 at 3:15 AM Kagami Rosylight <sascha...@outlook.com> wrote: > I want to find a way to replace cancellation token in the current [stage 1 > cancelable promise proposal]( > https://github.com/tc39/proposal-cancelable-promises) with an alternative > way which does not require passing an additional parameter. > > > > Here is a short representation of [my current thought]( > https://github.com/SaschaNaz/cancelable): > > > > ```ts > > // A cancelable object supports new `Symbol.cancel`. > > // `object[Symbol.cancel]()` will cancel any tasks related to the object. > > interface Cancelable { > > [@@cancel](): void; > > } > > > > interface Promise extends Cancelable {} > > ``` > > > > ```js > > // Here, a new `chain` object from promise constructor callback will > > // help chaining cancelable tasks and provide cancellation related > > // helper functions. > > > > function foo() { > > return new Promise(async (resolve, reject, chain) => { > > await nonCancelableSubWork1(); > > chain.throwIfCanceled(); // This line will throw `Cancel` object if > the promise got a cancellation request > > await nonCancelableSubWork2(); > > resolve(); > > }); > > } > > > > function bar() { > > return new Promise(async (resolve, reject, chain) => { > > // This `chain()` call will register foo() to the cancellation chain > of a promise instance > > // and will propagate cancellation to the chained tasks. > > // The chain can receive any object that supports `Symbol.cancel`. > > await chain(foo()); > > await chain(baz()); > > }); > > } > > > > const promise = bar(); > > promise.cancel(); // This will cancel `bar` call and the cancellation will > propagate to `foo` and `baz` > > ``` > > > > And with some syntax sugar for readability: > > > > ```js > > cancelable function foo() { > > // `chain` is a keyword inside cancelable function blocks > > await nonCancelableSubWork1(); > > chain.throwIfCanceled(); // similar form like `new.target` > > await nonCancelableSubWork2(); > > } > > > > cancelable function bar() { > > chain foo(); > > chain baz(); > > } > > > > const promise = bar(); > > promise.cancel(); > > > > cancelable function baz() { > > try { > > chain baw(); > > } > > else { > > // try-else block will catch cancellation, as the current existing > proposal does > > } > > } > > ``` > > > > I think this will achieve easier and more readable flow of cancelable > tasks, what do you think? > _______________________________________________ > es-discuss mailing list > es-discuss@mozilla.org > https://mail.mozilla.org/listinfo/es-discuss > -- mark Sent while riding a hoverboard... heyimmark.com :)
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