SvelteKit ignores page directives in +page.server.js

[acarl005]

Describe the bug

I have an app with pre-rendered pages. I'm NOT explicitly listing the pre-rendered pages in the svelte config, I'm letting the crawler discover them automatically. After migrating to 1.0.0-next.408 with the new routing, the pre-render crawler seems to be skipping pages if both of the following are true:

1. the page is behind a redirect
2. the page URL has a [param]

It was working before the routing overhaul. See the stackblitz link below for a repro. The /foo route redirects to /foo/bar which is handled by /foo/[slug]/+page.svelte. The /foo2 route redirects to /foo2/bar2 which DOES NOT have a param, it just resolves to /foo2/bar2/+page.svelte. Both page options are prerender = true, and both are linked from the home. The first is NOT prerendering but the second is. In the repro, run npm run build to see that 1 is getting prerendered which the other is not.

Before routing overhaul

This was working before the routing overhaul. Previously, I was doing my redirect within a standalone endpoint with something like

export async function GET() {
  return {
    headers: {
      location: `/newpath`
    },
    status: 302
  }
}

I also notice that the logs when I used to npm run build used to acknowledge my redirect:

10:05:52 AM: .svelte-kit/output/server/immutable/chunks/Container-0a471dd0.js             0.53 KiB
10:05:52 AM: .svelte-kit/output/server/immutable/chunks/EnrichedMarkdown-324634e1.js      11.89 KiB
10:05:52 AM: .svelte-kit/output/server/immutable/chunks/SchemaLabel-59931fc3.js           7.15 KiB
10:05:52 AM: .svelte-kit/output/server/immutable/chunks/hooks-3a5209ad.js                 1.72 KiB
10:05:52 AM: (node:1377) ExperimentalWarning: buffer.Blob is an experimental feature. This feature could change at any time
10:05:52 AM: (Use `node --trace-warnings ...` to show where the warning was created)
10:05:53 AM:   302 /course -> /course/lessons/what-is-sql
10:05:58 AM: 1/1 clients in student pool are ready
10:06:03 AM: 1/1 clients in student pool are ready
10:06:03 AM: vite v3.0.2 building for production...
10:06:03 AM: transforming...
10:06:03 AM: ✓ 2 modules transformed.
10:06:03 AM: rendering chunks...

But now this no longer seems to be happening.

Reproduction

https://stackblitz.com/edit/sveltejs-kit-template-default-btjtae?file=src%2Froutes%2Ffoo2%2Fbar2%2F%2Bpage.js&terminal=dev

Logs

No response

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (4) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 16.14.2 - /usr/local/bin/node
    Yarn: 1.22.10 - /bin/yarn
    npm: 7.17.0 - /bin/npm
  npmPackages:
    @sveltejs/adapter-auto: next => 1.0.0-next.64 
    @sveltejs/kit: next => 1.0.0-next.406 
    svelte: ^3.46.0 => 3.49.0

Severity

blocking an upgrade

Additional Information

No response

[Rich-Harris]

There's a couple of things going on here. While prerendering, SvelteKit will bail on any page that is not prerenderable, which includes /foo because there's no export const prerender (and config.kit.prerender.default isn't true). Right now it only respects export const prerender in +page.js, not +page.server.js — that's a bug.

If you change it back to what you were doing before...

// src/routes/foo/+server.js
import { redirect } from '@sveltejs/kit';

/** @type {import('./$types').RequestHandler} */
export async function GET() {
  return new Response(undefined, {
    status: 302,
    headers: {
      location: '/foo/bar'
    }
  });
}

...then it will work, because it doesn't have a concept of 'prerenderable endpoints'. That's something we plan to change: #4093.

[acarl005]

@Rich-Harris Thanks for the help. I changed it back redirect in a standalone endpoint instead of the page endpoint and now it works.

[Rich-Harris]

re-opening until we fix the 'SvelteKit ignores page directives in +page.server.js' bug

[acarl005]

Works great! Thanks!!