Set custom header for fetchRequestHandler

Is this possible? currently getting cors issue. Trying to use nextjs's edge function with trpc..

import { type NextRequest } from "next/server";
import { appRouter, createContext } from "api";
import { fetchRequestHandler } from "@trpc/server/adapters/fetch";

export const config = {
  runtime: "edge",
};

export default async function handler(req: NextRequest) {
  if (req.method === "OPTIONS") {
    return new Response(null, {
      status: 200,
    });
  }

  return fetchRequestHandler({
    endpoint: "/api/trpc",
    router: appRouter,
    createContext,
    req,
    onError:
      process.env.NODE_ENV === "development"
        ? ({ path, error }) => {
            console.error(`[tRPC] failed on ${path}: ${error}`);
          }
        : undefined,
  });
}

You also need to set the cors response headers, it's not enough to just respond to an options request

yep i was wondering how i can do that

with fetchRequestHandler

or do i need to set it prior

It's a fairly common problem, which is often solvable with the npm cors package to save yourself pain

cuz I can easily do it with serverless function like this:

but idk how to do it with edge

Ah right edge, hm

If there's a 1st party way with your edge provider, I'd use that

But you can just set the response headers in your code

I'm neither a Next or Edge user though unfortunately

how so, im using nextjs aswell

.set function doesnt seem to work

when using edge

Honestly I'm not sure, I don't use this tech

I'd look for an answer for your specific provider

You might be able to modify the response before returning it

tRPC generally doesn't deal with CORS stuff though, it's left up to you not to abstract too many things away

i see i just thought u can pass it through createContext

although fetchRequestHandler seem to be getting its headers from the req directly

Just submitted a pr about https://github.com/trpc/trpc/tree/main/examples/next-edge-runtime, it doesn't seem to work anymore.

https://github.com/trpc/trpc/issues/4048

Fixed!