Light DOM slot forwarding throws error in SSR (@lwc/engine-server)

[nolanlawson]

Doing "light DOM slot forwarding" (i.e. renaming light DOM slots passed in to other slots) works in client-side rendering, but causes an error to be thrown during server-side rendering.

Repro: 391570c

This throws an error

Cannot read properties of undefined (reading 'find')

Here:

lwc/packages/@lwc/engine-server/src/renderer.ts

Line 262 in b9947b4

const attribute = element[HostAttributesKey].find(

The reason is that the element here is a "raw" type which doesn't have a HostAttributesKey:

[git2gus]

This issue has been linked to a new work item: W-17017336