Is the "onEnd" callback mandatory?

I have a use-case where I want to essentially pull the stream out of these callbacks before I use it.

return new Promise((resolve, reject) => {
  req.multipart(
    (field, filestream, originalFilename, encoding) => {
      resolve(filestream);
    },
    (err?: Error) => {
        // i don't care what happens here, i handle it elsewhere
    },
    {
      limits: {
        fileSize: TWO_MEGABYTES,
        fields: 0,
        files: 1,
      },
    },
  );
}

I’m trying to figure out if I have to worry about the onEnd call back as it just seems really verbose. I’d rather get access to the file that’s being uploaded and resolve/pipe it somewhere else and handle the errors there. As it looks now, it appears I can do that but also need to handle a seemingly arbitrary case around the onEnd callback. Usually I notice the events happen in the following order, but I’m wondering if under certain circumstances that could change:

1. resolve / pipe the file somewhere else
2. initiate a pipe or a read on the file in it’s new location (ie passed to another function somewhere else, for example trigger a stream upload to a blob storage)
3. the onEnd callback fires at somepoint.

I’m basically trying to see is there anything that can happen in step 3 that I wouldn’t be able to reasonably handle during step 2 in a different place? If so, it would be nice to figure out a clean way to make a promise implementation here.

[mcollina]

That will work.

[Eomm]

Oh, I understand.

Who is the streamwriter? Does it implement all the stream lifecycle?