Route params is empty if page not found (404)

[bjon]

Describe the bug

We have a setup like this: /[lang]/path1, /[lang]/path2, etc...

In layout.ts we get the lang from params, so we can fetch other stuff.
But when a page is not found, params is now an empty object.
This broke in v432 (#6174)

Reproduction

• npm create svelte@latest repro-6453
• create route src/routes/[test]
• move +page into src/routes/[test]
• add +layout.ts to src/routes

/** @type {import('./$types').LayoutLoad} */
export function load({ params }) {
  console.info("params", params);
}

• npm run dev
• test http://localhost:5173/repro (console should print params)
• test http://localhost:5173/repro/not-found (now params is empty)

Logs

No response

System Info

System:
    OS: Linux 5.10 Ubuntu 20.04.5 LTS (Focal Fossa)
    CPU: (24) x64 AMD Ryzen 9 3900X 12-Core Processor
    Memory: 12.22 GB / 15.59 GB
    Container: Yes
    Shell: 5.0.17 - /bin/bash
  Binaries:
    Node: 16.17.0 - /usr/bin/node
    npm: 8.15.0 - /usr/bin/npm

Severity

blocking an upgrade

Additional Information

No response

[Rich-Harris]

This is expected behaviour — if no route matched, there's no route to extract params from. You'll need to use a rest route as described here: https://kit.svelte.dev/docs/advanced-routing#rest-parameters

// src/routes/[test]/[...catchall]/+page.js
import { error } from '@sveltejs/kit';

export function load() {
  throw error(404);
}