KeepAlive with RouterView errors during SSR

[gryphonmyers]

Version

4.0.3

Reproduction link

https://github.com/gryphonmyers/vite-minimal-repro/tree/vue-router-repro

Run the "build" script to see the error.

Steps to reproduce

1. Create a wrapper component using the suggested setup of:

<router-view v-slot="{ Component }">
      <keep-alive>
        <component :is="Component" />
      </keep-alive>
    </router-view>

2. Configure a test route to render with any component
3. Attempt to SSR render that route

What is expected?

The wrapper component should be rendered as if the keep-alive wrapper were not there during SSR, then in client build, the SSR output should be preserved even while loading an async view component.

What is actually happening?

SSR build errors and cannot complete as long as keep-alive component is used.

[gryphonmyers]

This was a core bug