Telling deferred.errback from deferred.cancel

[Shashank]

In my understanding, Deferred.cancel always fires errback (unless the deferred is already finished). How do I differentiate, in the error handler, whether it has been called due to an error or due to a cancellation?

In v 1.4 checking the error.message text was one solution (admittedly not the best solution, but it worked). In 1.5 there is no such error message that one could use.

Setting a flag on the error being returned or adding a flag to the deferred object itself can solve the problem, e.g. this change against the trunk Index: _base/Deferred.js =================================================================== --- _base/Deferred.js (revision 23174) +++ _base/Deferred.js (working copy) @@ -281,6 +281,7 @@

error = new Error(error);

} error.log = false;

+ error.isDeferredCancelled = true;

deferred.reject(error);

}

}

[bill]

Not sure if this ticket is relevant anymore but assigning to Mark since it's about Deferreds.

[Mark Wubben]

With 1.8, cancel() by default rejects with an instance of dojo/errors/CancelError, so that's one way of knowing. This could be changed by the deferred though. Typically you'd only handle expected errors in the errbacks and let other errors bubble through the promise chain.

Closing this because there is no actual bug.