Is removing Content-Length from empty post a deliberate change?

[fredericDelaporte]

Performing an empty POST (await fetch('someEndPoint', { method: 'POST' }), without a body) on the server side with a Node.js v22 with its default configuration results in a request having a Content-Length header set as 0.

This is compliant with the RFC 9110, which states (emphasis mine):

A user agent SHOULD send Content-Length in a request when the method defines a meaning for enclosed content and it is not sending Transfer-Encoding. For example, a user agent normally sends Content-Length in a POST request even when the value is 0 (indicating empty content).

But if using in this same Node 22 with HTTP/2 enabled, the same empty POST does no more send a Content-Length header at all in the request. As the RFC states "SHOULD", not "MUST", that is compliant, but no more the recommended behavior.

I have searched for a relevant issue or PR about this change but was unable to find one. Was this a deliberate change, or an accidental one? I would like more information about this before eventually opening an issue.

Underlying issue: some servers reject with a HTTP 411 response POST requests not having a Content-Length at all, while those having no body but a Content-Length at 0 are accepted. One such server: IIS (Internet Information Server). Actually, that is worse, that is the underlying operating system which does so, see this Stack Overflow answer.

HTTP/2 enabled with:

  setGlobalDispatcher((new Agent({
    allowH2: true
  }))

[mcollina]

Thanks for reporting!

Can you provide steps to reproduce? We often need a reproducible example, e.g. some code that allows someone else to recreate your problem by just copying and pasting it. If it involves more than a couple of different file, create a new repository on GitHub and add a link to that.

[metcoder95]

If you can provide an MRP we can assess whereas was intentional or not; otherwise might be a bit complex to understand

[fredericDelaporte]

I have now narrowed it down to only enabling HTTP/2, even with the Undici version bundled with Node.js v22. I may see to add a test about that.

Switching to Undici 7 without enabling H2 keeps the Content-Length emitted as 0 on empty POST requests. Enabling the cache does not change that. Only enabling H2 causes the header to go missing.

[fredericDelaporte]

See #4612.

[mcollina]

I would say it's a bug

[fredericDelaporte]

May be fixed by #4613.