http: improving expectation handling

[jasnell]

PR nodejs/node-v0.x-archive#7132 proposed a possible improvement to Expect
handling in http but it never landed. There was a little bit of review, but the conversation
stalled out and the submitted (@alFReD-NSH) moved on to other things. The PR is not
going to be able to land, and it's not a major priority, but I wanted to capture the issue here
before closing the PR. There does not seem to be anything inherently wrong with the change,
it just does not appear to be a significant priority. Additional review is helpful tho.

/cc @indutny

[gyzerok]

@jasnell Can I try to get this one?

[mnot]

Note that there's a spec change here, see:
http://httpwg.github.io/specs/rfc7231.html#header.expect

A server that receives an Expect field-value other than 100-continue MAY respond with a 417 (Expectation Failed) status code to indicate that the unexpected expectation cannot be met.

...

Note: The Expect header field was added after the original publication of HTTP/1.1 [RFC2068] as both the means to request an interim 100 (Continue) response and the general mechanism for indicating must-understand extensions. However, the extension mechanism has not been used by clients and the must-understand requirements have not been implemented by many servers, rendering the extension mechanism useless. This specification has removed the extension mechanism in order to simplify the definition and processing of 100-continue.

[designfrontier]

If there is no one else tackling this I'd be happy to grab it and get a PR together. @gyzerok are you still working on this?

[guyellis]

@designfrontier let me know if you need a hand with this if/when you pick it up.

[designfrontier]

Ok will do, hoping to pick in the next week right after Christmas.

-Daniel

On Dec 21, 2015, at 6:20 PM, Guy Ellis notifications@github.com wrote:

@designfrontier let me know if you need a hand with this if/when you pick it up.

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