Test failure in EventStream SSE

[kolbma]

Description

While the test response::stream::sse::sse_tests::test_heartbeat is repeated multiple times in the test garnish and has been always successful, I got now one time an assertion failed.

Is anybody of you using EventStream SSE of Rocket and has seen any inexplicable outputs??!!

The result of the test looks like a memory corruption or a race in setting memory boundaries:

failures:

---- response::stream::sse::sse_tests::test_heartbeat stdout ----
thread 'response::stream::sse::sse_tests::test_heartbeat' panicked at 'assertion failed: `(left == right)`
  left: `"data:hello\n:\n\n\n"`,
 right: `"data:hello\n\n"`', core/lib/src/response/stream/sse.rs:795:9


failures:
    response::stream::sse::sse_tests::test_heartbeat

test result: FAILED. 64 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 3.06s

https://github.com/kolbma/Rocket/blob/e365ab9ba423cf90864749318b548731ee9dc8d3/core/lib/src/response/stream/sse.rs#L792-L795

To Reproduce

cd core/lib
c=0; rc=0 ; while [ "$rc" -eq 0 ] ; do cargo +stable test response::stream::sse::sse_tests::test_heartbeat ; rc=$? ; c=$((c+1)) ; done ; echo "Failed after run $c"

Failed after run 7 or Failed after run 79.
But fails always if you try it often enough.

Expected Behavior

Test response::stream::sse::sse_tests::test_heartbeat should never fail.

Environment:

• OS Distribution and Kernel: Docker Alpine Linux
• Rocket Version: WIP v0.5.0-rc.2 #3

:: Preparing. Environment is...
  CARGO VERSION: cargo 1.58.0 (7f08ace4f 2021-11-24)
  RUSTC VERSION: rustc 1.58.0 (02072b482 2022-01-11)
  ROCKET VERSION: 0.5.0-rc.2

Additional Context

Need to stress test this some more.

[kolbma]

Looks like multiple events will be mixed up in the special handling of Rocket for \r and \n.