"API resolved without sending a response" false positive

[Janpot]

Bug report

Describe the bug

next api route logs

API resolved without sending a response for /graphql, this may result in stalled requests.

even though it sends a response;

To Reproduce

Set up a route like:

// /api/graphql.ts
import { createProxyMiddleware } from 'http-proxy-middleware';

export const config = {
  api: {
    bodyParser: false
  }
};

export default createProxyMiddleware({
  target: process.env.API_ENDPOINT,
  pathRewrite: { '^/api': '' }
});

And call it from the browser

Expected behavior

No unnecessary warning messages

System information

• Version of Next.js: 9.2.2

[jamesmosier]

Is this answer perhaps helpful? #10439 (comment)

"[Next] can't detect you are still doing work in the API unless you return a promise and wait to resolve it until after the callback is fired"

[Janpot]

If I forget to send a response, I will notice soon enough because my API wouldn't do anything. No need for a log message, especially not if it can't be correctly calculated when it should apply. Maybe a better heuristic would be to check whether

1. the handler returns a promise
2. that promise resolves with something else then undefined

and then log something like It seems like you try to return a value from an API handler, but you should use "res.send" instead

[balazsorban44]

This issue has been automatically locked due to no recent activity. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.