Debounce not working as expected (saving first value change instead of last one)

[Tarpsvo]

I'm submitting a bug report

• Library Version:
  1.0.0

Please tell us about your environment:

• Operating System:
  Windows 10
• Node Version:
  4.4.7
• NPM Version:
  3.10.6
• JSPM OR Webpack AND Version
  2.1.0-beta.21
• Browser:
  Chrome
• Language:
  ESNext

Current behavior:
The binding is as follows: if.bind="value > 0 & debounce:1000"
When value changes rapidly to 1 and then 0, and the debounce activates after 1 second, it will still use 1 as its value and the check will pass, even though value is 0.

Expected/desired behavior:
Expected result is to use the value that value is at the time of the debounce activation.

https://gist.run/?id=b0e5fd3fbaad39eb2b8b8fa6482d2589

[jdanyow]

https://gist.run/?id=065b5e45ea473fac03d98c85945739cf

[Tarpsvo]

Made an easier to read gist (also updated original post).

https://gist.run/?id=b0e5fd3fbaad39eb2b8b8fa6482d2589

[Tarpsvo]

@jsobell Made the following discovery:

https://gist.run/?id=765c24121f18196f73366f3fa4558fac
This is the problem you're seeing, and it's unrelated to the visual stuff
It should only be retaining the final state, and dropping the intermediate changes, but it looks like it's retaining the first change and dropping the others

[jsobell]

It's actually a bit more tricky than I thought.
Something related to the binding process (something Promise related?) prevents subsequent bindings being processed until the first has completed.
So if we make a call to the original binding (with any value) the debounce problem is avoided, as shown in this Gist.run:
https://gist.run/?id=4cfe4f76ee753b6660ad13ba60db8ddd
Obviously this is not ideal, but we need some way to inform the binding instance to no longer wait for a result, but to essentially cancel the current wait and we will initiate a new one when we're ready.
I'll ask @jdanyow about it when he wakes up.

[jsobell]

This only appears to affect checkbox bindings, as the effect is not observed on string inputs, although you also seem to have issues binding back to the UI with debounce (although that's a really weird thing to do)

[jdanyow]

@Tarpsvo I re-tested this- it looks like it might be working like you expect now:

https://gist.run/?id=065b5e45ea473fac03d98c85945739cf

I believe this might have been fixed by aurelia/templating@06be105 which closed a bunch of issues related to if.

Please take a look and let me know if this can be closed.

[Tarpsvo]

That's weird. The gist you linked still reproduces the same issue.

[maurice-camp]

Any update on this issue? I'm still experiencing it with aurelia-binding 1.0.9.
The gist you posted also still has this issue: The value appears to be updating to the value of the original change instead of the value of the last change.

[spookyvision]

for what it's worth, I'm having the same problem.

[thejaff2]

Also seeing this. My use-case below, isRequesting is true for less than 50ms, gets stuck as true in view. The same also happens when using throttle.

<loading-indicator loading.one-way="httpClient.isRequesting & debounce:200"></loading-indicator>

[spookyvision]

Anyone home..? I'd even fix the bug myself if somebody gave me a bit of help understanding the source (I've already tried and failed)

[jsobell]

Sorry, I'm not really involved at the moment, I have too much work to do that's not Aurelia related...

@jdanyow Are you still working on this stuff?

The issue relates to both show.bind and if.bind, as embedding the bound expression displays the correctly debounced value:

<p>Debounced: ${model.nr > 0 & debounce:2000}</p>