Empty formdata body stalls the parser

No full example yet, but the basic steps to reproduce would be this from a browser:

var xhr = new XMLHttpRequest();
var fd = new FormData();

fd.append('file', new Blob(), 'file.txt');
xhr.open('POST', '/');
xhr.send(fd);

The file event is raised correctly, but it seems to never emit a finish. I suspect the first empty file to be encountered will stall the whole upload request.

[mscdex]

@BlaM An easier way is to just do file.resume() if you want to skip over the current file.

Adding that in this module would not be acceptable however since busboy cannot make any assumptions about what the consumer of this module is doing. Adding a data handler or calling .resume() will cause the stream to flow. If someone needs to perform an async operation before reading from the file, they would lose data. All (“streams2” or newer) streams since node v0.10 start in a paused state. FWIW a similar issue may arise if you only read part of the file stream, since busboy also handles backpressure properly.

[BlaM]

Okay, I guess I start to understand now. There NEEDS to be someone listening to the file - if that does not happen, it will never reach “end”:

So if you do THIS:

        req.busboy.on('file', function(name, file, filename, encoding, mimetype) {
             if (!filename || filename === '') {
                return;
            }
            // do stuff if there is a filename
            file.pipe(....

This will freeze and stop doing things.

You need to at least have someone listening to “data”:

    file.on('data', function() {});

Adding this line into multipart.js right before the file.on("end") event fixed the problem for me, too. It should be in the code using busboy - but maybe having this blank “fallback data handler” in busboy itself might avoid confusion?