Better explanation of what SSR external/noExternal means

[mkilpatrick]

Documentation is

• Missing
• Outdated
• Confusing
• Not sure?

Explain in Detail

It would be helpful for the SSR external/noExternal options to explain what that really means in more detail. What does a noExternal dependency really mean? Does it mean the dependency is transformed by Vite? If so, what are the transformations? Is it the same as optimizeDeps? The optimizeDeps documentation is good as it explains what it's doing and its purpose.

Additionally, does external/noExternal affect dev only or also build? I think adding a little more to the docs here would be helpful for newer users.

Your Suggestion for Changes

See above

Reproduction

No response

Steps to reproduce

No response

[sapphi-red]

It has a link to https://vite.dev/guide/ssr.html#ssr-externals and that page describes a bit more in detail.

Additionally, does external/noExternal affect dev only or also build?

It applies to both dev and build.