Unmount hooks should be called during the commit phase to ensure consistency with React about preact

[JoviDeCroock]

They are called as part of the commit phase 😅 mind posting a reproduction or something we can base our discussion off of? Or do you mean deferring the hook cleanups? https://github.com/preactjs/preact/blob/main/hooks/src/index.js#L127

[farwayer]

Yes, you are right. I'm talking about calling the cleanup function of a child component while rendering the parent, if the child component is unmounted. The timing of the call is different from React and this sometimes causes problems.

let Parent = () => {
  console.log('parent render start')
  useLayoutEffect(() => console.log('parent render end'))

  let [showChild, setShowChild] = useState(true)

  useEffect(() => {
    setTimeout(() => setShowChild(false), 1000)
  }, [])

  return showChild ? <Child/> : null
}

let Child = () => {
  useEffect(() => () => console.log('child cleanup'), [])
  return null
}

React:

parent render start
parent render end
parent render start
parent render end
child cleanup

Preact:

parent render start
parent render end
parent render start
child cleanup
parent render end