[Breaking Change Request] [io/http] Drop Content-Length:0 header from CONNECT,DELETE,GET,HEAD requests

[aam]

Summary

We propose to not to include Content-Length header in CONNECT,DELETE,GET,HEAD http requests when its value is 0(when there is no body as part of http request).

Rationale

Presence of Content-Length:0 header runs against guidelines provided in RFC-7320 https://tools.ietf.org/html/rfc7230#section-3.3.2, which states that

A user agent SHOULD NOT send a
   Content-Length header field when the request message does not contain
   a payload body and the method semantics do not anticipate such a body.

The fact that dart:io HttpClientRequest code includes Content-Length:0 header in GET requests was recently found to be a culprit of inability for Dart http client code to talk to Google Cloud Run websocket services (see #45139). So this change will fix that problem.

See https://dart-review.googlesource.com/c/sdk/+/194881 for the actual change.

[aam]

@franklinyow, just wanted to let you know that announcement email has been sent out (https://groups.google.com/a/dartlang.org/g/announce/c/b0cncgjcRf4)

[rspilker]

What about other methods that also don't have defined semantics for a payload, like DELETE?

[aam]

@rspilker wrote

What about other methods that also don't have defined semantics for a payload, like DELETE?

Good question, thanks for pointing that out.
Per https://tools.ietf.org/html/rfc7231 It looks like DELETE and CONNECT in addition to GET and HEAD have similar language that "A payload within a ... request message has no defined semantics;
sending a payload body on a HEAD request might cause some existing
implementations to reject the request."
I believe we should extend proposed change to all four.

[aam]

any updates on this @franklinyow ?

[franklinyow]

Ping @vsmenon @matanlurey @Hixie for approval

[Hixie]

Following the standards SGTM.

[vsmenon]

lgtm

[franklinyow]

Approved

[daniel-mf]

Any updates?
Really would like to have this fixed so I could remove the massive workaround in my project.
Thanks!

[thomas-ferchau]

If I read the information in the commit correctly, the change is included in the dev releases since 2.14.0-181.0.dev

[aam]

Fixed in 6c254fa