Servo isn't exposing custom http response statuses to XHR

[pshaughn]

WPT xhr/status-async, xhr/status-basic and xhr/status-error expect to be able to see custom http statuses like "204 UNICORNSWIN" and "699 WAY OUTTA RANGE". Servo is instead showing out-of-range status numbers as 0, and is returning the standardized string meanings of in-range status numbers instead of the custom ones the server sent. I'm not seeing the list of standard status names within Servo's own source tree, so this must be involving another crate, maybe http.

In some cases in status-basic it looks like it's even interpreting the custom responses as a network error!

[pshaughn]

send-redirect-no-location and send-redirect-to-cors also fail like this.
edit: so do /xhr/send-contional and /xhr/send-conditional-cors
So does test2 of xhr/send-data-unexpected-tostring

[Darkspirit]

RUST_LOG=net ./mach test-wpt tests/wpt/web-platform-tests/xhr/status-basic.htm

servo/tests/wpt/web-platform-tests/xhr/status-basic.htm

Line 38 in cea55e3

statusRequest("CHICKEN", code, text, content, type)

servo/components/script/dom/request.rs

Line 516 in b274d59

HttpMethod::from_str(m)

It seems the CHICKEN request method is correctly set.

---

servo/tests/wpt/web-platform-tests/xhr/status-basic.htm

Line 41 in cea55e3

status(401, "OH HELLO", "Not today.", "")

• Status reason is read here:

  servo/components/net/http_loader.rs

  Lines 1454 to 1462 in 79408fa

  	response.status = Some((
  	res.status(),
  	res.status().canonical_reason().unwrap_or("").into(),
  	));
  	debug!("got {:?} response for {:?}", res.status(), request.url());
  	response.raw_status = Some((
  	res.status().as_u16(),
  	res.status().canonical_reason().unwrap_or("").into(),
  	));

  hyperium/hyper#135 added status_raw for this XHR use case. But as we can see above, Servo (now) uses canonical_reason() for both.

  That's because hyperium/hyper@3cd48b4#diff-80398c5faae3c069e4e6aa2ed11b28c0 and
  024b40b#diff-aa469beb5619907dbccd88364264b9b8L1088 removed the raw_status feature.

• HTTP/1.1 401 is Unauthorized by definition: https://tools.ietf.org/html/rfc7235#section-3.1.
  But RFC 2616 also says:

  The reason phrases listed here are only recommendations -- they MAY be replaced by local equivalents without affecting the protocol

  hyper's http crate reminds us:

  Bear in mind also that in HTTP/2.0 and HTTP/3.0 the reason phrase is abolished from transmission, and so this canonical reason phrase really is the only reason phrase you’ll find.

  Therefore canonical_reason() is only derived from status code (number).

  But the fetch spec possibly wants us to remove it when using HTTP/2: https://fetch.spec.whatwg.org/#concept-response-status-message says

  Responses over an HTTP/2 connection will always have the empty byte sequence as status message as HTTP/2 does not support them.

• Either HTTP/1.1 raw_status needs to be added back to hyper or information should be gathered whether this could be wontfixed or the spec be updated.