Specify range of valid HTTP response codes

[wingo]

What is the domain of wasi:http/response#set-status-code ?

RFC 9110 specifies the set of HTTP status codes, divided in 5 blocks (100-199, 200-299, 300-399, 400-499, 500-599), and specifies that new status codes should fall in those blocks.

Proposal: codes should be in the range 100-599.

FWIW, Rust's http crate allows 100-999, while "discouraging" codes 600 or above: https://github.com/hyperium/http/blob/master/src/status.rs#L73.

[igrep]

Doesn't it need to accept unofficially used status codes (such as 999)?

[wingo]

In the abstract it is better to use a field for that purpose, as fields are the extensible part of a response. Obviously if the use of e.g. 999 is widely-deployed we probably need to support it.

Interestingly I just read WhatWG fetch's specification, which allows 0..=999: https://fetch.spec.whatwg.org/#concept-status

I still think 100..-=599 is the right choice though if we manage to make it stick.