next.js file upload via api routes / formidable - not working

Question

I'm having a hell of a time getting file upload to work via api routes.

On client-side im submitting the file like so:

 onFormSubmit = (e) => {
    e.preventDefault() // Stop form submit

    this.fileUpload(this.state.file).then((response) => {
      console.log('rD', response.data)
    })
 }

 onFileChange = (e) => {
    this.setState({ file: e.target.files[0] })
 }

 fileUpload = (file) => {
    const url = '/api/mail/upload'
    const formData = new FormData()
    formData.append('file', file)
    const config = {
      headers: {
        'X-CSRF-TOKEN': this.props.session.csrfToken
      }
    }
    return axios.post(url, formData, config)
 }

My request to /api/mail/upload then looks like this:

Request Headers:
Accept: application/json, text/plain, */*
Accept-Encoding: gzip, deflate, br
Accept-Language: en-US,en;q=0.9,de-DE;q=0.8,de;q=0.7
Connection: keep-alive
Content-Length: 1331
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryBlNt6z8t4rGZT0x6
Cookie: abc123
Host: localhost:3000
Origin: http://localhost:3000
Referer: http://localhost:3000/new
Sec-Fetch-Mode: cors
Sec-Fetch-Site: same-origin
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.79 Safari/537.36
X-CSRF-TOKEN: abc123

Form Data:
file: (binary)

Then in the route (/api/mail/upload) I'm trying to use formidable to parse the form data and finally do something with the file.

I've made sure to disable the built-in body parser by including the following at the bottom of the api route file:

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

^^ Thats the correct way to do that, right?

Finally, in the api route, I've tried many different things, but currently the following is what I expect to work, but it is not..

module.exports = async (req, res) => {
  const form = new formidable.IncomingForm()

  form.parse(req, (err, fields, files) => {
    if (err) return reject(err)
    console.log(fields, files)
    res.status(200).json({ fields, files })
  })
  // if I console.log(form) here - I can see the request details, so it seems to be picking that up
}

This generates no output whatsoever on the server-side nor on client-side, i expect the console.log(fields, files) to output on the server-side the name of the file, etc.

Anyone know what I am missing?

Answer 1

All you need is disable Next.js built-in body parser: https://nextjs.org/docs/api-routes/api-middlewares#custom-config

Here are working example: https://gist.github.com/agmm/da47a027f3d73870020a5102388dd820