Argument is not a ByteString when setting headers with non-ASCII characters

[benmccann]

Bug Description

It looks like #1317 wasn't actually fixed

Reproducible By

I got this while setting the link header to the following value:

</_app/immutable/assets/__layout-a4ea7e9d.css>; rel="stylesheet"; nopush,</_app/immutable/start-cf8d1dd9.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/index-bf47b8b5.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/paths-98950022.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/preload-helper-c28b9807.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/singletons-1e28953d.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/env-public-887c86aa.js>; rel="modulepreload"; nopush,</_app/immutable/pages/__layout.svelte-b3b95660.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/navigation-c4179065.js>; rel="modulepreload"; nopush,</_app/immutable/pages/encoded/苗条.svelte-7e7988f6.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/stores-2e0a9bb3.js>; rel="modulepreload"; nopush

Expected Behavior

I think this should work. If it's invalid in some way, the error message should certainly be clarified. I passed a string which is valid, so it shouldn't be complaining about wanting a ByteString

Logs & Screenshots

TypeError: Argument is not a ByteString
    at Object.webidl.converters.ByteString (node_modules/.pnpm/undici@5.8.1/node_modules/undici/lib/fetch/webidl.js:404:11)
    at Headers.set (node_modules/.pnpm/undici@5.8.1/node_modules/undici/lib/fetch/headers.js:362:31)
    at render_response (packages/kit/test/apps/basics/.svelte-kit/output/server/_app/immutable/chunks/index-fb484aa3.js:1090:13)
    at respond$1 (packages/kit/test/apps/basics/.svelte-kit/output/server/_app/immutable/chunks/index-fb484aa3.js:2013:25)
    at resolve (packages/kit/test/apps/basics/.svelte-kit/output/server/_app/immutable/chunks/index-fb484aa3.js:2261:114)
    at packages/kit/test/apps/basics/.svelte-kit/output/server/_app/immutable/chunks/hooks-a33195ff.js:44:20
    at respond (packages/kit/test/apps/basics/.svelte-kit/output/server/_app/immutable/chunks/index-fb484aa3.js:2213:22)
    at packages/kit/src/vite/preview/index.js:142:5

Environment

Undici 5.8.1
Node 16.15.0
Ubuntu 22.04

Additional context

This is blocking the SvelteKit web framework from setting the link header

[ronag]

@KhafraDev

[KhafraDev]

This behavior is expected, you can test it for yourself in the browser console:

const headers = new Headers()
headers.set('link', '</_app/immutable/assets/__layout-a4ea7e9d.css>; rel="stylesheet"; nopush,</_app/immutable/start-cf8d1dd9.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/index-bf47b8b5.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/paths-98950022.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/preload-helper-c28b9807.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/singletons-1e28953d.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/env-public-887c86aa.js>; rel="modulepreload"; nopush,</_app/immutable/pages/__layout.svelte-b3b95660.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/navigation-c4179065.js>; rel="modulepreload"; nopush,</_app/immutable/pages/encoded/苗条.svelte-7e7988f6.js>; rel="modulepreload"; nopush,</_app/immutable/chunks/stores-2e0a9bb3.js>; rel="modulepreload"; nopush')

If it's invalid in some way, the error message should certainly be clarified.

Agreed, the errors around the webidl stuff should be improved.

I passed a string which is valid, so it shouldn't be complaining about wanting a ByteString

A ByteString is not a JS string; it can only contain ASCII and 8-bit characters (char codes between 128 - 255). The reason this string is throwing an error is because of the characters 苗条.

The webidl for the headers class indicates for implementations to convert both parameters of Headers.prototype.set to ByteStrings.

---

For more info, see:

• the webidl definition of ByteString - https://webidl.spec.whatwg.org/#idl-ByteString
• the conversion steps undici does to attempt to convert a string to a webidl bytestring (this is where an error is thrown) - https://webidl.spec.whatwg.org/#es-ByteString

[KhafraDev]

I'm going to re-open this until there are better error messages

[benmccann]

Thanks for the clarification! The improved error will help some. I'd probably still be confused that it was trying to convert it to a ByteString as lib.dom.d.ts says value: string and MDN didn't mention this restriction either. I guess that's outside the realm of this repo, but maybe I'll try to send a PR to MDN at least

[benmccann]

I've updated MDN: mdn/content#19166

I'll leave updating TypeScript's lib.dom.d.ts for someone else