@astrojs/vercel endpoint breaks when sending set-cookie

[WesSouza]

What version of astro are you using?

1.6.10

Are you using an SSR adapter? If so, which one?

Vercel

What is the Node.js version?

18

What package manager are you using?

pnpm

What operating system are you using?

Mac

Describe the Bug

Trying to set a cookie within a Response fails because the code in request-transform.js calls a function that is not supported on Vercel's environment.

Unhandled Promise Rejection

TypeError: response.headers.raw is not a function
  at setResponse (file:///var/task/node_modules/.pnpm/@astrojs+vercel@2.3.4/node_modules/@astrojs/vercel/dist/serverless/request-transform.js:61:46)
  at Server.handler (file:///var/task/node_modules/.pnpm/@astrojs+vercel@2.3.4/node_modules/@astrojs/vercel/dist/serverless/entrypoint.js:22:11)
  at process.processTicksAndRejections (node:internal/process/task_queues:95:5

Rejection: TypeError: response.headers.raw is not a function
  at process.<anonymous> (file:///var/runtime/index.mjs:1194:17)
  at process.emit (node:events:525:35)
  at process.emit (node:domain:489:12)
  at emit (node:internal/process/promises:149:20)
  at processPromiseRejections (node:internal/process/promises:283:27)
  at process.processTicksAndRejections (node:internal/process/task_queues:96:32)

I'm confused on why the developers used that function instead of the result of .get.

Edit: Whie investigating to try to come up with a PR to fix this, I saw the code is copied from SvelteKit, which might ship a custom implementation of Response and Header that supports the non-standard .raw() call.

Given Headers is associated with fetch, which does not involve setting cookies, it seems it does not account for the exception where multiple Set-Cookie headers can be sent.

I'm still looking into other resources to see if there is a well-established approach, otherwise it seems we'll need to split the values manually, given Header.append will join headers with the same key with a comma.

Link to Minimal Reproducible Example

https://stackblitz.com/edit/github-axnai7?file=src%2Fpages%2Fredirect.ts

Participation

• I am willing to submit a pull request for this issue.

[bluwy]

It does seem like we're block on nodejs/undici#1437. SvelteKit seems to go with the split approach, and I don't think there's a nicer way too, so we might have to do that.

[bluwy]

Fixed in #5514