TabPane with unmountOnExit should retain transition

[sisp]

I would have expected TabPane to retain the transition even when unmountOnExit is true, but looking at the the source null is returned immediately rather than when onExited is triggered. Is this intended?

[jquense]

It should retain the transition, active isn't toggled to false until the transition calls it's onExited callback, at which point we render null so it's unmounted

[sisp]

I can't confirm that the transition is happening and unless I'm missing anything I don't see how it should happen given the source code.

The following snippet shows how the active prop is determined from the context:

active:
  props.active == null && key != null
    ? makeEventKey(activeKey) === key
    : props.active,

The <Transition /> component animates the transition when the active prop changes. But when unmountOnExit === true the <Transition /> component is not rendered with active === false because null is returned immediately (see here).

[jquense]

Sorry are you saying it is working but you don't understand why or it's not working?

[sisp]

It's not working for me and the source code doesn't look like it's doing the right thing either.

[jquense]

Ok probably a bug then

[sisp]

I've put together a small example based on the custom tabs layout example from the docs: https://codesandbox.io/s/xl5n993np4

Change the unmountOnExit prop of the App component to see the difference and notice that unmountOnExit === true prevents animated transitions.

[jquense]

yup you're right, I think that one line should be !active && !Transition && unmountOnExit

[fungjj92]

Bump! Hi project maintainers. Can we get the proposed fix above in? I can make a PR if you'd like. I actually started, but thought I'd bump this issue first before putting in too much time to accumulate PR detail. Happy to do whatever is most helpful! Thanks.

[taion]

We'd be happy to take a PR here.

[taion]

fixed in #4312