By "incomplete" hostname, I mean a hostname that's entirely part of some rule or rules but does not have enough labels to match the rule or rules entirely. Examples of such hostnames are yokohama.jp and kobe.jp.

The relevant rules for those hostnames are:-

jp
*.kobe.jp
*.yokohama.jp
!city.yokohama.jp

I have seen these two, interpreted differently by at least two implementations and I understand how it can go either way. libpsl returns the public suffices for those domains as yokohama.jp and kobe.jp respectively. Servo's net_traits crate, however, returns jp for both, which leads to weird test cases like these.

What's the official position on this?