1034599 - Convert remaining Promise.defer() uses to PromiseUtils.defer() or to an inline helper

Status: RESOLVED FIXED

(Toolkit :: Async Tooling, defect, P1)

Description

[:Irving Reid (No longer working on Firefox)]

Promise.jsm provides a non-standard way of constructing new Promises, using the Promise.defer() static method.

Because ES6 standardized "new Promise(function(resolve, reject){..})" as the way of constructing Promises, we should officially deprecate Promise.defer().

Comment 1

[:Paolo Amadini]

The first step is addressing the dev-doc-needed from bug 941757 on MDN:

https://developer.mozilla.org/en-US/docs/Mozilla/JavaScript_code_modules/Promise.jsm

We may at the same time add deprecation notes to the existing documentation.

After this is done, we should find all the "defer" calls in mozilla-central and either:
- Convert to them "new Promise" directly, or
- Replace "Promise.defer" calls with a local helper (that only calls "new Promise"),
  and file a bug against the component for the final conversion to "new Promise".

When there are no more mozilla-central calls, we can add a deprecation warning to the API itself to get add-ons converted as well.

All this work is required for migration to DOM Promises when ready.

Comment 2

[Akshendra Pratap Singh]

David, can we use the defer defined in Promise-backend.js or is there any problem in that approach?

Comment 3

[Akshendra Pratap Singh]

Oops sorry for comment 2

Comment 4

[David Teller [:Yoric] - still alive but not very active]

Well, we can't call it, because it is going to disappear, but the same implementation should work.

Comment 5

[Florian Quèze [:florian]]

Attachment: promise.defer calls not replaced by script

Here is the output of my script from bug 1362882, listing the Promise.defer calls it didn't dare replacing, and explaining why.

Comment 6

[Florian Quèze [:florian]]

Attachment: Patch

This handles only the Firefox code. Test, mobile and devtools code will be for follow-up (and I'm not volunteering to fix them).
This is mostly done by hand, although I sometimes used some help from the bug 1362882 script (when converting to new Promise() after tweaking a bit the original file to let the script pass).

Comment 7

[Florian Quèze [:florian]]

Attachment: Patch (diff -w)

Diff -w version of attachment 8880184 [details] [diff] [review] for easier review.

Comment 8

[Mike Conley (:mconley) (:⚙️)]

Comment on attachment 8880184 [details] [diff] [review]
Patch

Review of attachment 8880184 [details] [diff] [review]:
-----------------------------------------------------------------

::: toolkit/components/jsdownloads/src/DownloadCore.jsm
@@ +840,5 @@
>        return Promise.resolve();
>      }
>  
> +    if (!this._promiseRemovePartialData) {
> +      this._promiseRemovePartialData = (async () => {

Whoa, today I learned about async () => {}

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/ea3fb9e7622e
Convert remaining Promise.defer() uses to PromiseUtils.defer() or new Promise(), r=mconley.

Comment 10

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/ea3fb9e7622e