Requests can hang with malformed JSONs; depends on error handling

Jayden,

Great work on the library, and thanks for pushing guys @ Apollo. Your workaround works well enough so that I wouldn’t care about them fixing their own dependency.

I am now using graphql-upload@8.0.1 with Express and have found this one rather small issue.

In the express middleware you have written code which (please correct me if I am wrong) is meant to delay the final response until the upload has ended:

• https://github.com/jaydenseric/graphql-upload/blob/master/src/graphqlUploadExpress.mjs#L36

• https://github.com/jaydenseric/graphql-upload/blob/master/src/graphqlUploadExpress.mjs#L32.

The issue is that the finished promise is listening for request.on("end"), which apparently doesn’t happen if an error occurs while uploading. Scenario is this:

1. Send a malformed request (e.q. an invalid operations JSON).
2. Have an error handler, which uses request.send (or .json - it resolves to .send). E.g. I have this little piece:

app.use((err, _, res, __) => {
  res.status(err.status).json({
    message: httpStatus[err.status],
    stack: config.printErrorStack ? err.stack : {}
  });
});

When .json() is called, the flow goes to your middleware:

https://github.com/jaydenseric/graphql-upload/blob/master/src/graphqlUploadExpress.mjs#L36

However, in this scenario the end event is never fired on the request. Two workarounds are available:

1. Use response.end() instead of .send() or .json(). I’d like to stick with .json, however.
2. Manually emit the end event in case of an error: request.emit("end").

Questions to you:

1. Do I understand your code correctly?
2. Do you know why the end event is not firing in case of an error in the upload middleware?
3. Does emitting end manually seem like a good fix which can be applied now?
4. Would you fix this? I guess you could do this using processRequest.catch() but I am not sure what your desired outcome would be in this case.

[jaydenseric]

The fix is published in graphql-upload@8.0.2, thanks all 🙌

[juona]

Thank you, the explanation makes sense : ]

Come to think of it, I did notice that smaller JPEGs seemed to work differently, i.e. would sometimes return responses, but the behaviour was inconsistent and I couldn’t understand what was going on, so I didn’t mention it in the description.

Happy to see smart people working on packages that I use - makes me feel secure ^^