Fast expand/collapse of folder leads to inconsistent state

[zadam]

Hello, I stumbled upon a bug which leads to inconsistent expanded/collapsed state of folder nodes when quickly toggling between expanded and collapsed state using keyboard shortcuts.

Could be that the problem lies in the fact that expand is triggered before the animation of the preceding collapse action has not finished yet.

Expected and Actual Behavior

See here how the inconsistent state looks like:

Expander is expanded, but children are not shown. Also note the debug message in console.

And corresponding (inconsistent) DOM view:

Steps to Reproduce the Problem

You can use http://jsfiddle.net/mar10/KcxRd/ to test this

1. Activate "folder 3" node
2. Very quickly in succession press right arrow (expand), left arrow (collapse), right arrow (expand)
3. Observe inconsistent state. Sometimes you need multiple tries to get this effect

Environment

• Browser type and version: Firefox 79, but I saw this happen also on Chrome 84
• jQuery and jQuery UI versions: jQuery 3.5.1
• Fancytree version: 2.36.1
  enabled/affected extensions:

[mar10]

The problem occurs when a second expand/collapse request is triggered while the previous animation is still running.
I changed the behavior so that in this case setExpanded() is ignored, with a warning.

(A better solution may be to stop the previous animation and then apply the new request, however this would be much more difficult to implement. Also, the first caller may wait for and process the done()callback of the original promise.)