Where to best run redirect on TRPCError({ code: "UNAUTHORIZED" });

[jpainam]

Hi.
In api/trpc.ts, we have this condition

if (!ctx.session?.user) {
    throw new TRPCError({ code: "UNAUTHORIZED" });
}

I'm wondering where we need to catch this error, to run a nextjs redirect to a custom login page.

I've added this in the nextjs/app/api/[...route]/route.ts

...
const handler = auth(async (req) => {
  try {
 
    const heads = new Headers(req.headers);
   // added custom headers
    const response = await fetchRequestHandler({
      endpoint: "/api/trpc",
      router: appRouter,
      req,
      createContext: () =>
        createTRPCContext({
          session: req.auth,
          headers: heads,
        }),
      onError({ error, path }) {
        console.error(`>>> tRPC Error on '${path}'`, error);
        // added this
        if (error.code == "UNAUTHORIZED") {
          redirect("/auth/login");
        }
      },
    });

    setCorsHeaders(response);
    return response;
  } catch (e) {
    console.error(">>> tRPC Error", e);
    const error = e as TRPCError;
     // added this
    if (error.code == "UNAUTHORIZED") {
      redirect("/auth/login");
    } else {
      throw e;
    }
  }
});

export { handler as GET, handler as POST };

But it doesn't work.

If i add redirect in api/trpc.ts, it shows this (even after adding redirect in the finally block).

o [TRPCError]: UNAUTHORIZED
    at /app/apps/nextjs/.next/server/chunks/6532.js:1:1126
    at r (/app/apps/nextjs/.next/server/chunks/2381.js:1:90577)
    at next (/app/apps/nextjs/.next/server/chunks/2381.js:1:90689)
    at /app/apps/nextjs/.next/server/chunks/6532.js:1:915
    at r (/app/apps/nextjs/.next/server/chunks/2381.js:1:90577)
[TRPC] student.count took 0ms to execute
    at e (/app/apps/nextjs/.next/server/chunks/2381.js:1:90919)
    at /app/apps/nextjs/.next/server/chunks/2381.js:4:1361
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
  code: 'UNAUTHORIZED',
  [cause]: undefined
}
Error: NEXT_REDIRECT
    at c (/app/apps/nextjs/.next/server/chunks/3145.js:1:55251)
    ... 8 lines matching cause stack trace ...
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
  code: 'INTERNAL_SERVER_ERROR',
  name: 'TRPCError',
  digest: '212336672',
  [cause]: Error: NEXT_REDIRECT
      at c (/app/apps/nextjs/.next/server/chunks/3145.js:1:55251)
      at l (/app/apps/nextjs/.next/server/chunks/3145.js:1:55466)
      at /app/apps/nextjs/.next/server/chunks/6532.js:1:1407
      at r (/app/apps/nextjs/.next/server/chunks/2381.js:1:90577)
      at next (/app/apps/nextjs/.next/server/chunks/2381.js:1:90689)
      at /app/apps/nextjs/.next/server/chunks/6532.js:1:915
      at r (/app/apps/nextjs/.next/server/chunks/2381.js:1:90577)
      at e (/app/apps/nextjs/.next/server/chunks/2381.js:1:90919)
      at /app/apps/nextjs/.next/server/chunks/2381.js:4:1361
      at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
    digest: 'NEXT_REDIRECT;replace;/auth/login;307;',
    mutableCookies: f {
      _parsed: [Map],
      _headers: Headers {
        'set-cookie': '__Secure-authjs.session-token=eyJhbGcih=/'
      }
    }
  }
}```