False positive prefetch external error when deployed to GitHub pages

Describe the bug

Not quite sure what’s going wrong and if this is really a bug or misconfiguration on my part.

Trying to deploy this app to GitHub pages at https://janosh.github.io/periodic-table, all internal links log console errors:

Uncaught (in promise) Error: Attempted to prefetch a URL that does not belong to this app: https://janosh.github.io/periodic-table/polonium

The error is raised here:

https://github.com/sveltejs/kit/blob/f87d55b6d5d425c395e0c2585da28fdf1e27ab81/packages/kit/src/runtime/client/client.js#L217

and might be due to URLs incorrectly classified as external here (hard to say with minified stack trace in prod and can’t reproduce in dev)

https://github.com/sveltejs/kit/blob/f87d55b6d5d425c395e0c2585da28fdf1e27ab81/packages/kit/src/runtime/client/client.js#L1002-L1003

data-sveltekit-prefetch is set globally on the body.

Reproduction

Doesn’t repro on StackBlitz as I think it’s related to serving the app on a non-root URL with a <base> tag as suggested in #7733.

Logs

No response

System Info

System:
    OS: macOS 13.0
    CPU: (10) arm64 Apple M1 Pro
    Memory: 88.06 MB / 16.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 18.9.0 - /opt/homebrew/bin/node
    npm: 8.19.1 - /opt/homebrew/bin/npm
  Browsers:
    Brave Browser: 107.1.45.127
    Chrome: 107.0.5304.110
    Safari: 16.1
  npmPackages:
    @sveltejs/adapter-static: 1.0.0-next.48 => 1.0.0-next.48 
    @sveltejs/kit: 1.0.0-next.553 => 1.0.0-next.553 
    svelte: ^3.53.1 => 3.53.1 
    vite: ^3.2.4 => 3.2.4

Severity

annoyance

Additional Information

No response

[dummdidumm]

The docs are correct. They omitted the alternative way with the base path though, which we should probably add (it has caveats though, which is why it’s left out though).

What I mean is that you add the base setting to your svelte.config.js like you did here and adjust your base path injection here to <base href={base} /> (with import { base } from '$app/paths'), but don’t adjust all your <a href tags, and then report back if this worked.

[janosh]

Sorry, for some reason I thought I saw a commit where you did <a href="{base}/path/to/page">...</a>.

Yes, there was one. I force-pushed. Sorry for the confusion. That commit had the same external prefetch console errors though.