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tikv / rust-prometheus

Prometheus instrumentation library for Rust applications
Apache License 2.0
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LabelPair PartialOrd inconsistent with PartialEq #513

Open rtimush opened 6 months ago

rtimush commented 6 months ago

Describe the bug PartialOrd is implemented manually for prometheus::proto::LabelPair and it only compares the name. However, PartialEq is derived, so it checks all fields. This violates PartialOrd requirements (a == b if and only if partial_cmp(a, b) == Some(Equal)) and may cause issues if LabelPair is used in standard containers.

To Reproduce

let mut a = LabelPair::new();
a.set_name("name".to_owned());
a.set_value("a".to_owned());

let mut b = LabelPair::new();
b.set_name("name".to_owned());
b.set_value("b".to_owned());

assert!(a.cmp(&b) == Ordering::Equal);
assert_eq!(a, b) // fails

Expected behavior Either PartialEq should be implemented manually to only compare the name field for consistency with PartialOrd, or PartialOrd should compare all fields. It's also worth mentioning in the docs if only name constitutes the equality, as it can be quite surprising.

Additional context I had a bug because tried to put LabelPair into a BTreeSet.