Issue with `trailingSlash` and prerendered routes

[yellowby]

Describe the bug

I have a website with prerendered pages running via adapter-node. The problem is that users sometimes use trailing slash in URLs. In this case, the loaded page looks like it has no css loaded, but with the correct content. I would expect a redirect to the URL without a trailing slash.

What is the expected behavior in this case?

https://sveltekit-trailing-slash.vercel.app/test

https://sveltekit-trailing-slash.vercel.app/test/

Reproduction

Demo: https://sveltekit-trailing-slash.vercel.app/

Repository: https://github.com/yellowby/sveltekit-trailing-slash

Logs

No response

System Info

System:
    OS: Windows 10 10.0.22621
    CPU: (16) x64 Intel(R) Core(TM) i9-9900K CPU @ 3.60GHz
    Memory: 38.98 GB / 63.93 GB
  Binaries:
    Node: 18.13.0 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.19 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
    npm: 8.19.3 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Spartan (44.22621.1105.0), Chromium (109.0.1518.69)
    Internet Explorer: 11.0.22621.1
  npmPackages:
    @sveltejs/adapter-auto: ^1.0.2 => 1.0.2
    @sveltejs/adapter-node: ^1.1.4 => 1.1.4
    @sveltejs/kit: ^1.0.0 => 1.3.1
    svelte: ^3.54.0 => 3.55.1
    vite: ^4.0.0 => 4.0.4

Severity

annoyance

Additional Information

No response

[Rich-Harris]

It looks like you mean adapter-vercel rather than adapter-node?

The expected behaviour is that /test/ redirects to /test, so that relative asset paths are correct. It looks like the routes config generated by adapter-vercel is incorrect though.

[yellowby]

@Rich-Harris Sorry for the confusion (should post screenshots from localhost and adapter-node). The issue affects both adapter-node and adapter-vercel.

It looks like you mean adapter-vercel rather than adapter-node?

The expected behaviour is that /test/ redirects to /test, so that relative asset paths are correct. It looks like the routes config generated by adapter-vercel is incorrect though.

[eltigerchino]

Should the trailing slash redirect logic be moved from the adapters to instead be part of server.respond as a fallback? or a helper function that adapters can use?

[Rich-Harris]

It is part of server.respond — adapters just need to be careful about not responding with foo/index.html for /foo or foo.html for /foo/, and letting SvelteKit handle the request instead. Unfortunately in the adapter-node case I think this might involve hacking around sirv