[QUESTION] Busboy and Expressjs - response not sent back to the client if next(new Error(...)) is called inside "file" event about busboy HOT 1 CLOSED

There are a few issues I see with the code you've posted:

1.    if (req.complete) {
        return;
      }

   is not correct, you should always consume file whether you're interested in it or not if you have a 'file' event handler. At the minimum that means using something like file.resume(); before your return.

2. Using the filename as-is like that puts you at risk for security issues if the filename is maliciously crafted (e.g. contains a relative path to escape your upload directory).

3. If the request is still pending after you've verified a response has been sent, then perhaps something (in Express or elsewhere) is still waiting for the request to be completely drained. If that's the case, you'll need to add something like req.resume() after you req.unpipe(busboy) to ensure any remaining data is drained out.

from busboy.