api endpoint hangs and eventually times out when you res.status(204).send('anything') instead of throwing an error

[anguskeatinge]

What version of Next.js are you using?

11.1.0

What version of Node.js are you using?

14 (hosted on vercel)

What browser are you using?

chrome

What operating system are you using?

macOS

How are you deploying your application?

Vercel

Describe the Bug

res.status(204) // works as expected
res.status(200).send('message') // works as expected
res.status(204).send('something') // shits itself

The request hangs and eventually gives a timeout error.
It took me way longer to debug this than it should have. Completely my fault, I admit it.

This isn't an issue when running the app with yarn dev
It's only an issue for me when it is deployed on vercel.

reminder: http code 204 = no response

Expected Behavior

Some options:

1. throw an error when attempting to send any data when the status is 204
2. make the function typesafe so it can't call .send() if the status is a 204
3. anything that would have made life a bit easier if there is a sneaky 204 in your code that is meant to be a 200.
4. at the very least, having consistent behaviour between the dev environment and the deployed app would make this much faster to spot.

To Reproduce

res.status(204).send('message') when deployed on vercel

[styfle]

This looks like a nasty bug, thanks!

May I ask, what is the use case for setting status code 204 (No Content) and then providing content anyway?

[anguskeatinge]

Sorry if I wasn't clear, there is no use case.

It came about because I was refactoring some code and added some response data to an endpoint that had previously been a 204 and I didn't think to update the http status.

The bug is that it causes the lambda to hang until timeout without any error or warning in the code or in typescript.

[styfle]

This has been fixed in 11.1.1-canary.16.

You can try it out now with yarn add next@canary, thanks!

[anguskeatinge]

Wow, you guys got on this fast. Solid.

Thanks @styfle 🚀

[balazsorban44]

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