prerendering broken when using a base path

[Tahlaria]

Describe the bug

When using adapter-static with a base path to build a project the pages won't be built (at least don't appear in build).
There is NO error message on build!
Affected versions: 1.0.0-next.231 and 232, <=230 aren't affected

Reproduction

Link to repository:
https://github.com/Tahlaria/svelte-build-bug

Branch main: works - version 230 referenced in package.json
Branch broken: doesn't work - version next referenced in package.json (232 right now)

npm i && npm run build
ls build

How to do yourself:
Checkout a skeleton project:
npm init svelte@next app
cd app

Import adapter-static:
npm i -D @sveltejs/adapter-static@next

Adapt svelte.config.js according to adapter instructions and use a base path:
svelte.config.js:

import adapter from '@sveltejs/adapter-static';

/** @type {import('@sveltejs/kit').Config} */
const config = {
        kit: {
                adapter: adapter({
                        pages: 'build',
                        assets: 'build',
                        fallback: null,
                        precompress: false
                }),

                // hydrate the <div id="svelte"> element in src/app.html
                target: '#svelte',
                paths: {
                        base: "/foo"
                }
        }
};

export default config;

Build:
npm i
npm build

Logs

### Build console output with next (right now 1.0.0-next.232)

<omitted>@<omitted>:~/Temp/app$ npm run build

> app@0.0.1 build /home/<omitted>/Temp/app
> svelte-kit build

vite v2.7.12 building for production...
✓ 13 modules transformed.
.svelte-kit/output/client/_app/manifest.json                    1.15 KiB
.svelte-kit/output/client/_app/layout.svelte-2102a60c.js        0.53 KiB / gzip: 0.35 KiB
.svelte-kit/output/client/_app/error.svelte-ef333d6a.js         1.56 KiB / gzip: 0.75 KiB
.svelte-kit/output/client/_app/pages/index.svelte-fdf0b640.js   0.80 KiB / gzip: 0.47 KiB
.svelte-kit/output/client/_app/chunks/vendor-f0095a1c.js        7.21 KiB / gzip: 2.96 KiB
.svelte-kit/output/client/_app/start-f26d2edf.js                21.60 KiB / gzip: 7.36 KiB
vite v2.7.12 building SSR bundle for production...
✓ 11 modules transformed.
.svelte-kit/output/server/manifest.json                    0.87 KiB
.svelte-kit/output/server/app.js                           48.60 KiB
.svelte-kit/output/server/entries/pages/layout.svelte.js   0.24 KiB
.svelte-kit/output/server/entries/pages/error.svelte.js    0.72 KiB
.svelte-kit/output/server/entries/pages/index.svelte.js    0.32 KiB
.svelte-kit/output/server/chunks/index-2dc61825.js         2.24 KiB

Run npm run preview to preview your production build locally.

> Using @sveltejs/adapter-static
  Wrote site to "build"
  ✔ done
<omitted>@<omitted>:~/Temp/app$ ls build
_app  favicon.png

### Build console output with (1.0.0-next.230 and lower):

> app@0.0.1 build /home/<omitted>/Temp/app
> svelte-kit build

vite v2.7.12 building for production...
✓ 13 modules transformed.
.svelte-kit/output/client/_app/manifest.json                    1.15 KiB
.svelte-kit/output/client/_app/layout.svelte-2102a60c.js        0.53 KiB / gzip: 0.35 KiB
.svelte-kit/output/client/_app/pages/index.svelte-fdf0b640.js   0.80 KiB / gzip: 0.47 KiB
.svelte-kit/output/client/_app/error.svelte-ef333d6a.js         1.56 KiB / gzip: 0.75 KiB
.svelte-kit/output/client/_app/chunks/vendor-f0095a1c.js        7.21 KiB / gzip: 2.96 KiB
.svelte-kit/output/client/_app/start-f26d2edf.js                21.60 KiB / gzip: 7.36 KiB
vite v2.7.12 building SSR bundle for production...
✓ 11 modules transformed.
.svelte-kit/output/server/manifest.json                    0.87 KiB
.svelte-kit/output/server/app.js                           48.42 KiB
.svelte-kit/output/server/entries/pages/layout.svelte.js   0.24 KiB
.svelte-kit/output/server/entries/pages/error.svelte.js    0.72 KiB
.svelte-kit/output/server/entries/pages/index.svelte.js    0.32 KiB
.svelte-kit/output/server/chunks/index-2dc61825.js         2.24 KiB

Run npm run preview to preview your production build locally.

> Using @sveltejs/adapter-static
  Wrote site to "build"
  ✔ done
<omitted>@<omitted>:~/Temp/app$ ls build
_app  favicon.png  index.html

System Info

System:
    OS: Linux 5.11 Ubuntu 20.04.3 LTS (Focal Fossa)
    CPU: (12) x64 Intel(R) Core(TM) i7-6800K CPU @ 3.40GHz
    Memory: 24.02 GB / 31.27 GB
    Container: Yes
    Shell: 5.0.17 - /bin/bash
  Binaries:
    Node: 14.18.3 - /usr/bin/node
    npm: 6.14.15 - /usr/bin/npm
  Browsers:
    Chrome: 97.0.4692.71
    Firefox: 96.0
  npmPackages:
    @sveltejs/adapter-auto: next => 1.0.0-next.11 
    @sveltejs/adapter-static: ^1.0.0-next.26 => 1.0.0-next.26 
    @sveltejs/kit: 1.0.0-next.230 => 1.0.0-next.230 
    svelte: ^3.44.0 => 3.46.2 

Note: @sveltejs/kit was tested with multiple versions:
.230 -> OK
.231 -> fail
.232 -> fail

Severity

serious, but I can work around it

Additional Information

Not a problem if it's known that <=230 isn't affected, otherwise it's breaking build functionality with static adapter (other adapters untested!).

[benmccann]

When you share a reproduction, please share a broken version! It took me forever to figure out why I couldn't reproduce the issue and that you had pinned an old version of SvelteKit in your package.json

[benmccann]

This line is being hit, so nothing is being rendered:

kit/packages/kit/src/runtime/server/index.js

Line 125 in f78c620

if (!decoded.startsWith(options.paths.base)) return;

It looks like prerendering does not include the base path in any of its requests

Probably was broken by #3345

[lemmon]

I have [probably] the same issue, starting v 231. However, I haven't applied any special settings for kit.paths nor the adapter. Everything is set to default.

The only affected file is favicon.ico.

HTTP/1.1 404 Not Found
Content-Length: 9

But the very same file renamed to favicon2.ico works just fine:

HTTP/1.1 200 OK
Content-Length: 61

Every other file seems to be working just fine.