Adding a progback causes returned promise to be resolved when progress is emitted

[Mark Wubben]

signalListener in dojo/Deferred unexpectedly resolves the promise's internal deferred when a progback function is available.

var dfd = new Deferred();
var p = dfd.then(null, null, function(){});
dfd.progress();
// p.isFulfilled() --> true

Given that I found this myself I suppose not many people are using progress updates…

[Mark Wubben]

There's a patch at <​https://github.com/novemberborn/dojo/commit/8f626cc419338c4bd0477039213453f09d987e4f>.

The patch comes with a small feature change: if the progback returns a value (that is not undefined), a new progress update is emitted on the returned promise. This makes it possible to propagate progress updates through a promise chain without having to explicitly break the change with other deferreds. Given that nobody else has found this bug before I think this is unlikely to break existing code.

[Mark Wubben]

Bryan, would you be my review buddy on promise code? :-)

[Mark Wubben]

In [29702]:

Improve handling of progback results

• Don't resolve the returned promise
• If the progback returns a value, emit that value on the returned promise as a progress update, allowing for easier update propagation

Fixes #15996, !strict

[bill]

Looks like you forgot to backport to 1.8 branch?

[Colin Snover]

In [29736]:

Improve handling of progback results

• Don't resolve the returned promise
• If the progback returns a value, emit that value on the returned promise as a progress update, allowing for easier update propagation

Fixes #15996, !strict
Backport to 1.8.