Entering/Exiting flipped for last item in transition group

[bookman25]

What is the current behavior?

When removing/adding items in a transition group:

1. When removing the first item and adding an item to the end, first item stays in place until removed.
2. When removing the last item and adding an item to the end, last item swaps place with the item being added.

What is the expected behavior?

When removing the last item, it should retain it's position until completely removed. Entering and Existing items should not swap places while in transition.

Remove the first item, list order stays consistent. Entering item appears at the end of the list and exiting item retains its position.
Remove the bottom item, entering/exiting items swap places. Entering item appears above item being exited.
https://codesandbox.io/s/k9xx51p555

Maybe the same bug as: #410

[bookman25]

We don't know where to place the pending item to be removed from the old list in the new list because nothing comes after this pending item to be removed in it's current list. There is an assumption that there will be an item in the new list to reinsert the pending items to be removed into, otherwise it just adds them to the end. It doesn't handle the case where pending items to be removed have a previous item above them in the grouping that could be used as a reference point.
https://github.com/reactjs/react-transition-group/blob/master/src/utils/ChildMapping.js#L54

[theredtankod]

Any news on a potential fix for this bug?

[silvenon]

No 😕 It's unexpected behavior for sure, I'll see what we can do about it when I find some time.

[XtolotosX]

I have a similar issue, when i delete an item somewhere in the middle of a list, the item to delete is changing the place with the item below and then the animation starts.