I'm getting this error

Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'length')

at https://github.com/preactjs/preact/blob/bb804cd317ed641bad3527d2d39e24e1d948fa41/src/component.js#L100

if I modify a file that has a component rendered inside a portal and that threw an exception on initial render. The property in question is _children on VNode.

It looks like vnodesForComponent isn't cleared in catchError, and it seems _children isn't initialized if initial rendering fails. Not sure if this is a Preact or Prefresh issue, but since the component is unmounted on error, Prefresh shouldn't try to re-render it.

I can only seem to trigger this when the component in question is in a portal, though I haven't been able to figure out why that's special.

When I first tried to make a StackBlitz repro, this didn't trigger. After upgrading to the latest versions of Vite, Preact and preact-vite, the issue started showing.

Repro

https://stackblitz.com/edit/create-preact-starter-ttn2e8qn?file=src%2Fresource.jsx

1. Load the StackBlitz.
2. The "Error: Intended" will show in the console.
3. Make a change in resoure.jsx and wait a bit for HMR.
4. The "TypeError: Cannot read properties of undefined (reading 'length')" will show in the console.