Hi Tony,
On Wed, Jan 31, 2018 at 3:37 PM, commits@source.squeak.org wrote:
A new version of Kernel was added to project The Inbox: http://source.squeak.org/inbox/Kernel-tonyg.1148.mcz
==================== Summary ====================
Name: Kernel-tonyg.1148 Author: tonyg Time: 31 January 2018, 11:37:21.27021 pm UUID: 2a675301-406b-4222-9599-84358a7cc506 Ancestors: Kernel-eem.1147
Brings the Promise implementation closer to Javascript/A+ promises in two ways: * Resolving a Promise with another Promise causes them to be chained together * Resolving or Rejecting a Promise that is not pending is a no-op, like the Firefox/Chrome/etc in-browser promise implementations. The tests have been changed in KernelTests-tonyg.331 accordingly.
=============== Diff against Kernel-eem.1147 ===============
Item was changed: Object subclass: #Promise
instanceVariableNames: 'value resolvers mutex state errorrejecters'
instanceVariableNames: 'onError value resolvers mutex state errorrejectors rejecters' classVariableNames: '' poolDictionaries: '' category: 'Kernel-Processes'!
- !Promise commentStamp: 'tonyg 1/31/2018 23:34' prior: 0!
- !Promise commentStamp: 'fbs 5/17/2013 18:23' prior: 0! I represent the result of an asynchronous message. Once the message is
processed, I will be resolved to a value. I am typically instantiated by invocations of #futureSend:at:args: (and not by #futureDo:atArgs:).
See class-comment of FutureNode.
I also implement the Promises/A+ Javascript specification. This allows you to chain my instances to perform arbitrarily complex asynchronous tasks with error handling baked in.
- A Promise may be in one of three possible states: #pending, #fulfilled
or #rejected. A Promise may move from #pending -> #fulfilled (by way of the resolveWith: message), or from #pending -> #rejected (by way of rejectWith:). No other state changes may occur.
- Once #fulfilled or #rejected, a Promise's value must not change. In
keeping with the major Javascript Promise implementations' interpretations of this, calls to resolveWith: or rejectWith: when a Promise is in #fulfilled or #rejected state are simply ignored - an error is not signalled. (See test cases PromiseTest testFirstResolutionWins, testCannotRejectFulfilledPromise and testCannotResolveaRejectedPromise.)!
- A Promise may be in one of three possible states: #pending, #fulfilled
or #rejected. A Promise may move from #pending -> #fulfilled, or from #pending -> #rejected. No other state changes may occur. Once #fulfilled or #rejected, a Promise's value must change.!
Item was changed: ----- Method: Promise>>rejectWith: (in category 'resolving') ----- rejectWith: anObject "Reject this promise." mutex critical: [
(state == #pending) ifTrue: [error := anObject.state := #rejected.rejecters do: [:r | self evaluateRejecter: r]]]!
(state == #fulfilled) ifTrue: [self error: 'Promise wasalready resolved'].
(state == #rejected) ifTrue: [self error: 'Promise wasalready rejected'].
error := anObject.state := #rejected.rejecters do: [:r | self evaluateRejecter: r]].!Item was changed: ----- Method: Promise>>resolveWith: (in category 'resolving') ----- resolveWith: arg
"Resolve this promise. If arg is itself a Promise, make thispromise depend upon it,
as detailed in the Promises/A+ spec:https://promisesaplus.com/#the-promise-resolution-procedure"
(arg isKindOf: Promise)
I'd /much/ rather see Object>>isPromise and Promise>>isPromise than this.
ifTrue: [arg whenResolved: [:v | self resolveWith: v].arg whenRejected: [:e | self rejectWith: e]]ifFalse: [mutex critical: [(state == #pending) ifTrue: [value := arg.state := #fulfilled.resolvers do: [:r | selfevaluateResolver: r]]]]!
"Resolve this promise"mutex critical: [(state == #fulfilled) ifTrue: [self error: 'Promise wasalready resolved'].
(state == #rejected) ifTrue: [self error: 'Promise wasalready resolved'].
value := arg.state := #fulfilled.resolvers do: [:r |self evaluateResolver: r]].!Item was changed: ----- Method: Promise>>then: (in category 'monad') ----- then: resolvedBlock
^ self then: resolvedBlock ifRejected: [:e | "Pass rejectionreason along" e].!
^ self then: resolvedBlock ifRejected: [:ignored | "Do nothing"].!
_,,,^..^,,,_ best, Eliot