rtk test does not normalise an even, non-zero negation count — returns the child's status where a shell returns 0/1 #4289

rtk test applies the ! negation that the interposed sh -c string used to get from the shell. An odd count inverts the child's status, which is right. An even, non-zero count returns the child's status verbatim instead of normalising it to 0/1, so the answer can be a code no shell would give.

Found while reviewing #4125, on its head. Not a regression — see below — so it did not hold that PR.

Symptom

$ rtk test ! ( ! sh -c 'exit 2' )
exit 2
$ bash -c '! ( ! sh -c "exit 2" )'
exit 1

bash normalises: the result of a negation is a truth value, 0 or 1, never the operand's code. rtk returns 2, which reads as "the command failed with status 2" when what happened is "the doubly-negated condition is false".

Mechanism

src/main.rs, the Commands::Test arm:

if negations % 2 == 1 {
    i32::from(code == 0)
} else {
    code
}

The else is correct for negations == 0 and wrong for every even count above it. split_leading_negations peels !s and a wrapping ( … ) in a loop, so negations >= 2 arrives here from ! ! and, since #4125, from ! ( ! … ) as well.

Shape that closes it:

if negations % 2 == 1 {
    i32::from(code == 0)
} else if negations > 0 {
    i32::from(code != 0)
} else {
    code
}

Why this is not a regression

The merge-base answered 0 for the same input — a reported pass for a command that failed, because the joined sh -c string took a different route through the shell. So the current code moved the answer into the right direction (non-zero for a false condition) and stopped short of the right value. Worth fixing on its own terms rather than as a regression.

Test

tests/run_shell_test.rs::grouped_and_negated_commands_keep_their_exit_codes covers eight spellings but cannot see this: its ! ! ( true ) case uses true, whose status is already 0, so normalising and not normalising agree. A case whose child exits non-zero under an even negation count — ! ! sh -c 'exit 2', ! ( ! sh -c 'exit 2' ) — is what pins it, asserted against bash.