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tests: guard CacheStatus as_str/serde encodings against drift #58

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tests: guard CacheStatus as_str/serde encodings against drift #58

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3cc7483
tests: guard CacheStatus as_str/serde encodings against drift
cargo-affected-bot Jun 22, 2026
834cf90
Merge remote-tracking branch 'origin/main' into tests/cache-status-en…
cargo-affected-bot Jul 29, 2026
5ce2c93
docs: fully-qualify Display intra-doc link in CacheStatus::as_str
cargo-affected-bot Jul 29, 2026
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32 changes: 29 additions & 3 deletions src/report.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -89,9 +89,10 @@ pub(crate) enum CacheStatus {
}

impl CacheStatus {
/// Stable kebab-case string used by the JSON serializer and the
/// stderr summary line. One canonical mapping; the serde derive
/// uses the same encoding.
/// Stable kebab-case string for the stderr summary line (reached via
/// the [`std::fmt::Display`] impl). The serde derive independently produces the
/// same kebab-case encoding for JSON; these are two mappings that must
/// agree, and `cache_status_as_str_matches_serde` guards that they do.
pub(crate) fn as_str(self) -> &'static str {
match self {
Self::HitExact => "hit-exact",
Expand Down Expand Up @@ -837,6 +838,31 @@ mod tests {
assert_eq!(json, "\"hit-with-divergence\"");
}

/// `as_str` (stderr summary, via `Display`) and the serde derive (JSON)
/// are two independent kebab-case mappings that must produce the same
/// string for every variant. Guard the whole set so renaming one
/// encoding without the other fails loudly instead of silently drifting.
#[test]
fn cache_status_as_str_matches_serde() {
for status in [
CacheStatus::HitExact,
CacheStatus::HitWithDivergence,
CacheStatus::MissFingerprint,
CacheStatus::MissNoCoverage,
CacheStatus::MissNoReachableSha,
CacheStatus::ForcedAll,

@cargo-affected-bot cargo-affected-bot Jul 29, 2026

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This array is a third hand-maintained enumeration of the variants. as_str's match is exhaustive, so the compiler forces a new variant to be added there — but nothing forces it into this array, so a newly-added variant would silently escape the guard. That's the same silent-drift failure mode the PR is closing, just one level up.

A dependency-free way to make it fail loudly: drop an exhaustive match next to the array so adding a variant breaks compilation until it's listed here too, e.g.

// Compile-time reminder: a new variant must be added to the array above.
fn _exhaustive(s: CacheStatus) {
    match s {
        CacheStatus::HitExact
        | CacheStatus::HitWithDivergence
        | CacheStatus::MissFingerprint
        | CacheStatus::MissNoCoverage
        | CacheStatus::MissNoReachableSha
        | CacheStatus::ForcedAll => {}
    }
}

Not blocking — the current test fully covers the rename-one-encoding case it targets.

] {
let serde = serde_json::to_string(&status).unwrap();
assert_eq!(
serde,
format!("\"{}\"", status.as_str()),
"as_str and serde disagree for {status:?}",
);
// Display routes through as_str — keep it in the same guard.
assert_eq!(status.to_string(), status.as_str());
}
}

/// Stored fingerprint diff against current: differing labels are
/// the symmetric difference of (label, hash) sets.
#[test]
Expand Down
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