`--format=junit` doesn't include stdout / test failure reason

[ssbr]

I tried this code:

#[test]
fn it_breaks() { panic!("PANICCC"); }

I expected to see this happen: the string PANICCC in the test output, when running cargo test -- --format=junit -Zunstable-options.

Instead, this happened:

<?xml version="1.0" encoding="UTF-8"?><testsuites><testsuite name="test" package="test" id="0" errors="0" failures="1" tests="1" skipped="0" ><testcase classname="crate" name="it_breaks" time="0"><failure type="assert"/></testcase><system-out/><system-err/></testsuite></testsuites>

Meta

rustc --version --verbose:

rustc 1.68.2 (9eb3afe9e 2023-03-27)
binary: rustc
commit-hash: 9eb3afe9ebe9c7d2b84b71002d44f4a0edac95e0
commit-date: 2023-03-27
host: x86_64-unknown-linux-gnu
release: 1.68.2
LLVM version: 15.0.6

[Manishearth]

Note that this works fine under other message formats

[Manishearth]

Ah, it seems like the JSON backend emits this as a "stdout" entry

rust/library/test/src/formatters/json.rs

Lines 139 to 144 in 5546cb6

	let display_stdout = state.options.display_output || *result != TestResult::TrOk;
	let stdout = if display_stdout && !stdout.is_empty() {
	Some(String::from_utf8_lossy(stdout))
	} else {
	None
	};

Whereas the junit backend does not

The test runner maintains a distinction between TrFailed and TrFailedMsg, except that the latter is only for failures with messages that come from the test suite (as opposed to panic messages). The testsuite doesn't distinguish between panic messages and otherwise, though it can for should_panic tests.

The simplest thing to do is probably just dump stdout inside the failure text body. I'm not sure if that's ideal, it would be nice if we could get it into message instead.