+server.ts API endpoint fails to parse body

[callmeberzerker]

Describe the bug

The only file new file in the blank svelte-kit project is the +server.ts located in src/routes/api/+server.ts. It just echoes the incoming JSON. Hitting http://localhost:5173/api (with content-type and accept headers set to application/json and body { "sample": "test"} ) will return HTTP 400 Bad request -> and the request never hits the API endpoint.

If I remove the content-type and accept headers it will enter the API endpoint but it would error out on await request.json() with:

Unexpected end of JSON input
SyntaxError: Unexpected end of JSON input

It might be a Windows issue but honestly I am not sure and can't test atm.

Reproduction

https://github.com/callmeberzerker/body-not-working

Run pnpm install and then pnpm dev.

Logs

Sadly there are none.

System Info

System:
    OS: Windows 10 10.0.22621
    CPU: (16) x64 Intel(R) Core(TM) i9-9900K CPU @ 3.60GHz
    Memory: 16.30 GB / 31.92 GB
  Binaries:
    Node: 19.0.0 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.19 - C:\Program Files\nodejs\yarn.CMD
    npm: 8.19.2 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Spartan (44.22621.674.0), Chromium (105.0.1343.42)
    Internet Explorer: 11.0.22621.1
  npmPackages:
    vite: ^3.2.0 => 3.2.0

Severity

blocking all usage of SvelteKit

Additional Information

N/A

[georgdonner]

I ran into the exact same issue today setting up a new Sveltekit project and am on MacOS, so it's probably not a Windows issue. It might be related to #5370, because I am seeing the same error "Invalid request body"

[Rich-Harris]

Oddly, I can reproduce this by cloning the repo, but as soon as I add a pnpm override to start debugging it, it works... a true Heisenbug 🤔

[callmeberzerker]

Thanks for the response - I almost went crazy trying out different things for this seemingly straight-forward thing!

[Conduitry]

I think this is due to the new version of undici that was just released a few hours ago. Its Request implementation is throwing RequestInit: duplex option is required when sending a body. for the incoming request.

[Conduitry]

Yeah, when I override to 5.11.0, things seem to work fine. The obvious change in 5.12.0 that would be causing this is nodejs/undici#1681 but I haven't dug any further into what this was intended to do or whether this is a new bug there or what.

[Conduitry]

I'm marking this as urgent. It might be a good idea to pin to undici 5.11.0 if we can't immediately see how we should now be calling Request now or if it looks like the new behavior is a bug.

[callmeberzerker]

Yep, I can confirm pinning undici@5.11.0 via pnpm.overrides (https://pnpm.io/package_json#pnpmoverrides) fixed the issue on my project for the time being. Thanks! 🙌

[KhafraDev]

This change is expected, see
whatwg/fetch@edf07e5#diff-b4827ee42aceaf9dc3e7216f72262d81c32217e9996fb70a657f259e3ac92604R6898-R6899

[careerlister]

Is there a work around or will the patch be coming soon?

[Conduitry]

Until #7412 is released, the workaround is to use overrides to force undici@5.11.0.