Inconsistencies in XHRUpload's response handling

Trying out Uppy, I’m facing a blocker. I don’t think Uppy forwards me the server response, which means I can’t let the user know what happened if the server rejects the uploaded file.

Here is the code I wrote:

link(scope, elem, attrs) {
    const uppy = Uppy({
        id: attrs.id,
        autoProceed: true,
    })
    .use(DragDrop, { target: `#${attrs.id}` })
    .use(XHRUpload, {
        endpoint: `${attrs.url}`,
        headers: {
            authorization: 'Basic dGVzdDp0ZXN0Cg==',
        }
    })
    .run();

    uppy.on('complete', (result) => {
        console.log('successful files:', result.successful)
        console.error('failed files:', result.failed)
    });
}

That console.error gives me one item in result.failed

{
  "source": "DragDrop",
  "id": "uppy-transfersexport120120181147csv-2493-1515754039000",
  "name": "transfers_export_12_01_2018 11_47.csv",
  "extension": "csv",
  "meta": {
    "name": "transfers_export_12_01_2018 11_47.csv",
    "type": null
  },
  "type": null,
  "data": {
    "fullPath": "/transfers_export_12_01_2018 11_47.csv"
  },
  "progress": {
    "percentage": 100,
    "bytesUploaded": 2944,
    "bytesTotal": 2944,
    "uploadComplete": false,
    "uploadStarted": 1515761105337
  },
  "size": 2493,
  "isRemote": false,
  "remote": "",
  "error": "Upload error"
}

The server answered with

{
  "timestamp": "2018-01-12T12:43:18.71",
  "status": 422,
  "error": "Unprocessable Entity",
  "path": "/api/v1/transfers/payload_upload",
  "data": "Not a zip file"
}

[bertho-zero]

On my side I did not set up the server side route, so I have a 404 error but I can not get an error on my

// autoProceed: false

try {
  const uploadResult = await this.uppy.upload();
} catch ( error ) {
  console.log('Error on upload:', error.message || error);
}

I have tried this in getResponseError:

return new Error( 'Gnégnégné, ça marche pas !' );
// or
return { message: 'Gnégnégné, ça marche pas !' };
// or
return { error: 'Gnégnégné, ça marche pas !' };
// or
throw new Error( 'Gnégnégné, ça marche pas !' );

All files are in the successful key.

[kvz]

We think this was solved, if not, feel free to re-open!