Uploading empty files when the content type is 'multipart/form-data'

Hi, I am using your library to upload base64 images. My setup follows the multipart/form-data example from the docs:

const imageData = 'iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAFklEQVR42mNk+H/iPwMRgHFUIX0VAgAmtxvHR58D2wAAAABJRU5ErkJggg=='

RNFetchBlob.fetch(
  'POST',
  'http://localhost:12345/api/upload',
  {
    'Content-Type': 'multipart/form-data',
    'Authorization': 'Bearer ...',
  },
  [{
    name: 'file',
    filename: 'file.jpeg',
    type: 'image/jpeg',
    data: imageData,
  }],
);

The problem is that when I look at the files section of the request received by my Flask server, I get a file object with all the information provided in the body (name, type, etc.), but no content.

I tried uploading using 'Content-Type': 'octet-stream' and the data is properly loaded as binary, but I really need to send it to the server as multipart content.

Versions

react-native: 0.63.2
rn-fetch-blob: 0.12.0

joltup / rn-fetch-blob

Uploading empty files when the content type is 'multipart/form-data' #651