react-call-return: Expected to find a host parent.

[rmhartog]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
A specific order of unmounting and remounting unstable_createReturns from react-call-return causes an invariant violation in unmountHostComponents.

Reproduce
The following sandbox example crashes with an invariant violation when both the min and cycle props are odd numbers greater than zero.

https://codesandbox.io/s/llyjz19rz7

What is the expected behavior?
The app does not crash and cycles the number of items in the list.

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?
react and react-dom versions 16.1 and newer, react-call-return version 0.5.0

[rmhartog]

Performing the same sequence of mounts and unmounts with react-test-renderer causes the same error, so it appears that the bug occurs in the reconciler.

[gaearon]

Wanna try digging into where the bug is?

[gaearon]

Tagging as a good issue to get into, but it's not an easy one.

[rmhartog]

Yes, I'd love to dig into it further!

[gaearon]

Sounds good. You'll probably want to look at BeginWork, CompleteWork, and ChildFiber, and how those handle Calls and Returns. Let me know if some aspects are confusing and I can try to explain.

[rmhartog]

It seems like a minor mistake when reconciling the children, causing duplicate deletions in some cases. Opened a pull request for the changes.

[gaearon]

Fixed in #11979.

There are likely more bugs with call/return. If you can try to stress-test this feature and find them, that would be great!