Incremental Static Regeneration (ISR) not working with rest parameters

[pdrbrnd]

Describe the bug

A sveltekit project with ISR (vercel adapter) and the following structure:

routes/
├─ foo/
│  ├─ [...path]/
│  │  ├─ +page.svelte
│  ├─ +layout.server.ts (adding ISR)

will cause /foo to error when visiting directly or refreshing.
Other paths (like /foo/bar) will work.

It's possible to make it work by adding an extra page:

routes/
├─ foo/
│  ├─ [...path]/
│  │  ├─ +page.svelte
│  ├─ +layout.server.ts
│  ├─ +page.svelte --- HERE

Related with #10155 (possibly duplicated and, if so, I apologize)

I first encountered the issue when working on a project that has optional parameters with matchers and rest parameters ([[region=region]]/[[lang=lang]]/[...path]).
I kept removing parts and the issue seems to happen even with just the rest parameters.

Reproduction

Complete example with "workaround"
https://github.com/pdrbrnd/sveltekit-isr
https://sveltekit-isr-mu.vercel.app/

Minimal example
https://github.com/pdrbrnd/sveltekit-isr/tree/minimal
https://sveltekit-isr-git-minimal-pedrobrandao.vercel.app/

Logs

No response

System Info

System:
    OS: macOS 14.0
    CPU: (8) arm64 Apple M2
    Memory: 129.11 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.5.1 - ~/.nvm/versions/node/v20.5.1/bin/node
    Yarn: 1.22.19 - /opt/homebrew/bin/yarn
    npm: 9.8.0 - ~/.nvm/versions/node/v20.5.1/bin/npm
    Watchman: 2023.08.07.00 - /opt/homebrew/bin/watchman
  Browsers:
    Brave Browser: 115.1.56.20
    Chrome: 117.0.5938.132
    Safari: 17.0
  npmPackages:
    @sveltejs/adapter-auto: ^2.0.0 => 2.1.0
    @sveltejs/adapter-vercel: ^3.0.3 => 3.0.3
    @sveltejs/kit: ^1.20.4 => 1.25.1
    svelte: ^4.0.5 => 4.2.1
    vite: ^4.4.2 => 4.4.11

Severity

serious, but I can work around it

Additional Information

No response

[rohanrajpal]

Question, now if i invalidate this layout endpoint, will it invalidate all the endpoints in its children, or do i have to manually invalidate the specific child i have to?