question about /[fallback] route

[ivanhofer]

Can someone explain me this line of code?

kit/packages/kit/src/core/postbuild/fallback.js

Line 38 in 2f2ef5f

const response = await server.respond(new Request(config.prerender.origin + '/[fallback]'), {

I found this code when I was investigating this issue.
I assume this code should never be run? Ideally an adapter would provide a fallback functionality, right?

If not I find the behavior strange to fallback to an undocumented page, which will result either

• into an error, leaving the user clueless how to resolve the issue
• render a page with unexpected content
  when e.g. a route /[category] exists, it could render a page that won't be displayed correctly because [fallback] is probably not a valid category