People are confused by adapter-static

[elliott-with-the-longest-name-on-github]

Describe the problem

I've lost count of the number of times people have asked "why is my adapter-static build output missing index.html" (and other similar questions) in Discord. It's always fixed by either adding config.kit.adapter.fallback = 'foo.html' or config.kit.prerender.default = true. To be clear, this is in the documentation, and not having one of these settings does produce a yellow (?) warning during build, but I've found that people tend to lose the yellow warning in the output from build.

Describe the proposed solution

When trying to run svelte-kit dev or svelte-kit build, throw a full-on, red, crash-the-process error stating:

It looks like you're using adapter-static, but `config.kit.prerender.default` is `false` and `config.kit.adapter.fallback` is missing. Either set `config.kit.prerender.default` to true (to statically generate your entire site) or set `config.kit.adapter.fallback` to your desired fallback page (to operate in SPA mode). For more information, check out <link to FAQ in adapter-static docs about this issue>

Maybe I'm missing some context here, but I don't think there's any case where adapter-static should be run without one of those options set, and the fact that it "works" in dev confuses a lot of people.

Alternatives considered

No response

Importance

would make my life easier

Additional Information

Happy to work on this one if it's a feature we'd actually like to add.

[Mlocik97]

There are use cases when you want to use adapter-static without prerendering or fallback, anyway it's good to warn about this... not throw error.

[furudean]

There are use cases when you want to use adapter-static without prerendering or fallback

When?

[bothness]

I can second that this has been causing confusion for me. In earlier versions of Adapter Static, it was clear that you can render as a SPA by including config.kit.adapter.fallback, or pre-render all routes by including config.kit.prerender.enabled, but now I get messages suggesting that I need to use "hooks" to render as a SPA, but there isn't any documentation on how to do this.

[Rich-Harris]

Judging by the emoji reactions, this is something we should do. I also can't think of a situation where you'd want to use adapter-static without either prerendering by default or having a fallback.

[elliott-with-the-longest-name-on-github]

@Rich-Harris Consider it done