Correct way to identify empty response body

This would solve…

Even if there is no response body, undici handles it by returning a stream with 0 length. Currently the only way to tell if you should be trying to parse the body is response.body._readableState.length, which feels a lot like delving deep into internals.

The implementation should look like…

Additional getter on response would allow to solve this problem without performance overhead:

response.isBodyPresent // getter that checks _readableState.length

I have also considered…

This can also be addressed via documentation, if it is recommended to resolve this in a different way, e. g. by trusting statusCode === 204.

[mcollina]

A few notes:

1. a JSON is at least 2 bytes
2. a body can be zero length
3. a content-type of “application/json” guarantees at least two bytes

What I did in the past in those cases is to check the content-type header.

[mcollina]

Does undici lower-case headers it received in responses?

Yes it does.