"Expect: 100-continue" header is using case-sensitive comparison

[JonathanMurray]

Version
0.14 (and master-branch 2021-11-30)

Platform
Darwin C02Y72T1JGH5 20.6.0 Darwin Kernel Version 20.6.0: Mon Aug 30 06:12:21 PDT 2021; root:xnu-7195.141.6~3/RELEASE_X86_64 x86_64

Description
I have a service built with Hyper that I'm now trying to communicate with from a client written in Java. I noticed when doing this that Java's standard HttpClient sends 100-continue expectations as Expect: 100-Continue (https://github.com/AdoptOpenJDK/openjdk-jdk11/blob/master/src/java.net.http/share/classes/jdk/internal/net/http/Exchange.java#L408), whereas Hyper compares the expectation header value against 100-continue (case-sensitive) (

hyper/src/proto/h1/role.rs

Line 274 in 5f938ff

expect_continue = value.as_bytes() == b"100-continue";

). This has the effect that the Java client never receives a 100 Continue from the Rust service, which makes it seemingly unable to handle the response correctly. https://datatracker.ietf.org/doc/html/rfc2616#section-14.20 seems to state that the capitalisation of the 100-continue token should not matter from the server's perspective:

Comparison of expectation values is case-insensitive for unquoted
   tokens (including the 100-continue token), and is case-sensitive for
   quoted-string expectation-extensions.

Trying this:

changing the expect_continue_sends_100 test to send the request expectation with an upper-case C.

diff --git a/tests/server.rs b/tests/server.rs
index 13530a36..0b991337 100644
--- a/tests/server.rs
+++ b/tests/server.rs
@@ -808,7 +808,7 @@ fn expect_continue_sends_100() {
         b"\
         POST /foo HTTP/1.1\r\n\
         Host: example.domain\r\n\
-        Expect: 100-continue\r\n\
+        Expect: 100-Continue\r\n\
         Content-Length: 5\r\n\
         Connection: Close\r\n\
         \r\n\

and running cargo test --features full expect_continue_sends_100

I expect to see this happen:

test passes

Instead, this happens:

The test fails with:

---- expect_continue_sends_100 stdout ----
thread 'expect_continue_sends_100' panicked at 'read 1: Os { code: 35, kind: WouldBlock, message: "Resource temporarily unavailable" }', tests/server.rs:821:30
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace