Ability to customise API middleware error responses

[satazor]

Feature request

Is your feature request related to a problem? Please describe.

Next.js has API routes with built-in middlewares, such as bodyParser. When an error is thrown by those middlewares, Next.js sends an error response, handled by sendError.

The current implementation sends a JSON response with the error message as the body. As an example: if we send request, with Content-Type: application/json with an invalid JSON request body, the server responds with Invalid JSON.

However, usually APIs that I develop have a standard envelope for errors, like:

{
  "statusCode": 400,
  "message": "Invalid request body",
  "other": "optional stuff here"
}

I would like to be able to keep the same response envelope for built-in middleware errors.

Describe the solution you'd like

Perhaps, we could somehow be able to tweak the sendError by including it in the config exported in API routes?

export const config = {
  api: {
    sendError: (res, statusCode, message) => {},
  },
};

Describe alternatives you've considered

I've looked into the code to see if I could somehow monkey-patch to get around the issue temporarily, but I couldn't find a way. Another solution is to turn off all the middleware and use something like micro to have full-control, but seems overkill.

Additional context

[fastfrwrd]

maybe a pages/api/_error.ts could be good, it would feel similar to error handling on the React side of things.

[satazor]

maybe a pages/api/_error.ts could be good, it would feel similar to error handling on the React side of things.

That looks like a great idea actually!