next.359 - load fetch POST => Request with GET/HEAD method cannot have body

Describe the bug

In a load function of a page, doing a fetch to http://localhost:3000/api will throw an error:

Request with GET/HEAD method cannot have body.

Here is the code:

    const resultPOST = await event.fetch("http://localhost:3000/api", {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
      },
      body: JSON.stringify({
        hello: "World",
      }),
    });
    const jsonPOST = await resultPOST.json();

Info

I stripped down the reproduction to http://localhost:3000/api URL. But my use case will be to target other APIs not only locals one like ‘/api’

Reproduction

Here is the stackblitz: https://stackblitz.com/fork/github/jycouet/sk-359-post (fetch issue is happening, but the log is different than locally!)

Here is the minimal repo: https://github.com/jycouet/sk-359-post With the few step in git from npx create to the issue.

Logs

Request with GET/HEAD method cannot have body.
TypeError: Request with GET/HEAD method cannot have body.
    at new Request (file:///home/jycouet/udev/tmp/sk-359-post/node_modules/@sveltejs/kit/dist/node/polyfills.js:9104:14)
    at Agent$1.fetch (file:///home/jycouet/udev/tmp/sk-359-post/node_modules/@sveltejs/kit/dist/node/polyfills.js:10280:22)
    at fetch (file:///home/jycouet/udev/tmp/sk-359-post/node_modules/@sveltejs/kit/dist/node/polyfills.js:12200:22)
    at Object.fetch (file:///home/jycouet/udev/tmp/sk-359-post/.svelte-kit/runtime/server/index.js:2293:51)
    at load (index.svelte:17:35)
    at runMicrotasks (<anonymous>)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at async load_node (file:///home/jycouet/udev/tmp/sk-359-post/.svelte-kit/runtime/server/index.js:2394:12)
    at async respond$1 (file:///home/jycouet/udev/tmp/sk-359-post/.svelte-kit/runtime/server/index.js:2778:15)
    at async resolve (file:///home/jycouet/udev/tmp/sk-359-post/.svelte-kit/runtime/server/index.js:3291:11)

System Info

System:
    OS: Linux 5.4 Ubuntu 20.04.2 LTS (Focal Fossa)
    CPU: (8) x64 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
    Memory: 1.24 GB / 7.69 GB
    Container: Yes
    Shell: 5.0.17 - /bin/bash
  Binaries:
    Node: 16.15.1 - ~/.volta/tools/image/node/16.15.1/bin/node
    Yarn: 1.22.17 - ~/.volta/tools/image/yarn/1.22.17/bin/yarn
    npm: 8.3.0 - ~/.volta/tools/image/npm/8.3.0/bin/npm
  npmPackages:
    @sveltejs/adapter-auto: next => 1.0.0-next.53 
    @sveltejs/kit: 1.0.0-next.359 => 1.0.0-next.359 
    svelte: ^3.44.0 => 3.48.0 
    vite: 2.9.13 => 2.9.13

Severity

blocking an upgrade

Additional Information

It’s a blocker for our Library Houdini that was working well before next.359. We have an issue open here: https://github.com/HoudiniGraphql/houdini/issues/374

[GauBen]

Well, that was fast https://github.com/nodejs/undici/pull/1529#issuecomment-1178953790

[GauBen]

You can also try patching node_modules/@sveltejs/kit/assets/server/index.js:2304 with:

const external_request = new Request(requested, /** @type {RequestInit} */ (opts));
response = await options.hooks.externalFetch.call(null, external_request.url, external_request);

and restart the dev server.