Fields not being submitted from Uppy v3.4.0 to Transloadit

[dseravalli]

Initial checklist

• I understand this is a bug report and questions should be posted in the Community Forum
• I searched issues and couldn’t find anything (or linked relevant results below)

Link to runnable example

No response

Steps to reproduce

On Uppy v3.4.0

Uppy configuration

new Uppy.Uppy()
    .use(Uppy.Dashboard, {
      trigger: '.file-upload-btn',
    })
    .use(Uppy.RemoteSources, {
      companionUrl: Uppy.Transloadit.COMPANION_URL,
      companionAllowedHosts: Uppy.Transloadit.COMPANION_ALLOWED_HOSTS,
      sources: [
	'Box',
	'Dropbox',
	'GoogleDrive',
	'Instagram',
	'OneDrive',
	'Facebook',
	'Url',
      ],
    })
    .use(Uppy.Webcam, { target: Uppy.Dashboard })
    .use(Uppy.Audio, { target: Uppy.Dashboard })
    .use(Uppy.Form, {
      target: 'form',
      resultName: 'uppyResult',
      getMetaFromForm: true,
      addResultToForm: true,
      submitOnSuccess: false,
      triggerUploadOnSubmit: false,
    })
    .use(Uppy.Transloadit, {
      assemblyOptions (file) {
	return {
	  params: {
	    auth: { key: 'xxxx' },
	    template_id: 'xxxx',
	  },
	  fields: {
	    submissionId: '1234',
	  },
	}
      },
    });

I have also tried passing assemblyOptions as an object instead of a function.

Transloadit template:

{
  "steps": {
    ":original": {
      "robot": "/upload/handle"
    },
    "export": {
      "use": [
        ":original"
      ],
      "robot": "/s3/store",
      "bucket": "xxxx",
      "path": "${fields.submissionId}/${file.md5hash}/${file.url_name}",
      "acl": "bucket-default",
      "bucket_region": "us-east-1",
      "key": "xxxx",
      "secret": "xxxx"
    }
  }
}

Expected behavior

I expect submissionId to be present in the assembly JSON, and I expect my S3 paths to start with 1234

Actual behavior

submissionId is not present anywhere in transloadit UI or assembly JSON. S3 paths start with the MD5 hash instead of 1234

[rorito]

Can confirm we got hit by this same bug in testing upgrading to 3.4.0

[arturi]

Hi, thanks for reporting and sorry about this, we are looking into this.