This also occurs with redirects defined in next.config.js, see reproductions for Next 12.2 and Next 12.3 here https://github.com/codynova/next-middleware-redirects

This issue still persists in latest canary v13. It still prevents us from upgrading our apps.

This issue still persists on the new v14.0.0. We still cannot upgrade our apps without a major rewrite.

For anyone concerned with this issue - I have investigated further and found that this issue can be worked around in user-land.

TL;DR: The problem is prevented by not redirecting on a data request in the server-side part of a custom redirect function. Example below:

if (res) {
    const isDataReq = ctx.req?.headers["x-nextjs-data"]; // checking for a middleware data request prevents this issue

    if (!isDataReq) {
      // Server redirect
      res.writeHead(push ? 307 : 302, {
        Location: as || location
      });
    }

    res.end();
  } else {
  ...

To elaborate - the issue is caused by a redirected url being returned as an effect from the fetchData request in the withMiddlewareEffects function in router (

It would be great to have this handled internally in next, so userland does not have to rely on fixing a common pattern used for routing in nextjs < 10.

This issue has been automatically marked as stale due to two years of inactivity. It will be closed in 7 days unless there’s further input. If you believe this issue is still relevant, please leave a comment or provide updated details. Thank you.