Posting object to Google Cloud Storage doesn't replace ${filename} variable

Question

As described here https://cloud.google.com/storage/docs/xml-api/post-object

I can use ${filename} as part of the key when uploading a file to GCS from the browser (using a signed request).

That's great, because it's the exact same variable S3 uses. But - a problem. It doesn't actually replace ${filename} with the name of the file when I upload. This works perfectly on S3, but with GCS I literally get $%7Bfilename%7D as the key in the response - clearly it's not replacing this with the correct value.

I'm building the request like so:

export function uploadVideo(video) {
  return new Promise((resolve, reject) => {
    if (!video) {
      resolve(null);
      return;
    }
    // this fetches a presigned post object from the server:
    request.get('/presigned_post')
      .query({format: 'json'})
      .end((err, response)=> {
        if (!err && response.ok) {
          request
            .post(`https://${response.body.url.host}/`)
            .field(response.body.fields)
            .field('Content-Type', image.type)
            .attach('file', image, image.name)
            .end((err, response) => {
              if (err) {
                console.log("Error uploading image: ", err);
                reject(err);
              } else {
                resolve({
                  location: response.text.match('<Location>' + '(.*?)' + '</Location>')[1],
                  bucket: response.text.match('<Bucket>' + '(.*?)' + '</Bucket>')[1],
                  key: response.text.match('<Key>' + '(.*?)' + '</Key>')[1],
                  checksum: response.text.match('<ETag>"' + '(.*?)' + '"</ETag>')[1]
                });
              }
            });
        }
      });
  });
}

The key is some_folder/${filename} and this is included in the form data to google (in response.fields ).

You can see I am providing the filename with .attach('file', image, image.name) . It is uploading correctly, just not replacing the ${filename} var.

edit

I have narrowed down the issue more. We query S3 and GCS to get the fields in the presigned post. With S3, if I give a key of ${filename} then I get exactly that returned in the fields:

  def presigned_post(bucket_name:, key:, **opts)
    response = s3_resource.
      bucket(bucket_name).
      presigned_post(key: key, content_type_starts_with: '', **opts)

    {
      fields: response.fields,
      url:    { host: URI.parse(response.url).host }
    }
  end

Fields here will contain "key"=>"${filename}" .

However in the GCS case, the following code returns :key=>"$%7Bfilename%7D" in the fields:

# https://cloud.google.com/storage/docs/xml-api/post-object#usage_and_examples
# https://www.rubydoc.info/gems/google-cloud-storage/1.0.1/Google/Cloud/Storage/Bucket:post_object
def presigned_post(bucket_name:, key:, acl:, success_action_status:, expiration: nil)
  expiration ||= (Time.now + 1.hour).iso8601

  policy = {
    expiration: expiration,
    conditions: [
      ["starts-with", "$key", "" ],
      ["starts-with", "$Content-Type", "" ],
      { acl: acl },
      { success_action_status: success_action_status }
    ]
  }

  post_obj = get_bucket!(bucket_name).post_object(key, policy: policy)

  url_obj = { host: URI.parse(post_obj.url).host }

  # Have to manually merge in these fields
  fields = post_obj.fields.merge(
    acl: acl,
    success_action_status: success_action_status
  )

  return { fields: fields, url: url_obj }
end

If i manually change the key in the GCS request fields, then it works. Is that really what I'm supposed to do?

Answer 1

A fix for this issue was released in google-cloud-storage v1.24.0 .

Answer 2

Figured out the issue is caused by:

      def ext_path
        URI.escape "/#{@bucket}/#{@path}"
      end

in lib/google/cloud/storage/file.rb of the google-cloud-ruby-gem.

This is called by def post_object in that same file.

I am going to raise an issue on their Github page.