No SSR output from components returned from defineComponent with extends or mixins

[gryphonmyers]

Version

3.0.5

Reproduction link

3aa6af4

Steps to reproduce

1. Wrap a component with defineComponent call using either mixins or extends options
2. Attempt to SSR the returned component
3. Observe that only a comment is rendered

What is expected?

Components extended with defineComponent should render their markup in SSR builds

What is actually happening?

Components extended with defineComponent are rendering comments instead of their expected markup in SSR builds