http: Stream#write with an empty buffer does not call callback

[RubenVerborgh]

When writing an empty buffer, Stream#write does not call the callback: https://github.com/nodejs/node/blob/v10.7.0/lib/_http_outgoing.js#L608

Is this intended? If so, this should probably be mentioned explicitly in the documentation.
If not, we might want to fix this.

[RubenVerborgh]

Note: it only hangs on empty buffers, not empty strings.

[addaleax]

I think this has come up before, in some form? It would be a breaking change but probably worth it.

/cc @nodejs/http

[amitzur]

I reported the original issue to axios. I now wonder how this code does work (or in other words how to reproduce with a minimal example):

process.stdout.write(Buffer.from(''), err => {
  console.log('done!', err);
});

output:

done! undefined

[RubenVerborgh]

@amitzur The code that returns early with an empty buffer is specific to HTTP, not to writable streams in general. Your example doesn't use HTTP, so that's why it works.

[amitzur]

ahh, right right.
It hangs also on empty strings. Which makes sense from the code at https://github.com/nodejs/node/blob/v10.7.0/lib/_http_outgoing.js#L608 but it doesn't explain why follow-redirects doesn't hang on empty strings.

For example:

require('http')
  .request({
    hostname: 'www.google.com',
  })
  .write('', err => {
    console.log('done', err);
  });

[mcollina]

Fixed in 413a7e1.

[RubenVerborgh]

It does not explicitly mention that the callback will not be called, however. So this doesn't address my original issue.

Also, please note that

it only hangs on empty buffers, not empty strings.

so this is a problem as well.

[RubenVerborgh]

@mcollina Do I create a new issue?

[mcollina]

It does not explicitly mention that the callback will not be called, however. So this doesn't address my original issue.

@RubenVerborgh I think it does 413a7e1#diff-69e1ac0b5bfc06e74f2c1ab7b062c6afR753 - When I read that, I assume nothing means nothing, including not calling the callback.

Would you like to send a PR with the text that would be ok for you?

it only hangs on empty buffers, not empty strings.

Can you please upload a snippet that show this? The check and the logic is identical, so I don't see how it's possible that the two call will behave differently Buffer.from('').length and ''.length both return 0.