The article makes the 'default' key with push_str("-default"), and given that, your approach should work. But i think that's a placeholder, and a bit of an odd one - i think it's more likely to see something like (pardon my rusty Rust) k = if let Some((head, _)) = k.split_once("_") { head.to_owned() } else { k } - so for example a lookup for "es_MX" will default to "es". I don't think your approach helps there.
Yeah, true. But that (assuming you're saying give me es_MX if it exists otherwise es) has a similar possible solution. Model your Language and variants hierarchically rather than flat. So languages.get("es_MX") becomes
let language = languages.get_language("es");
let variant = language.get_variant("MX");
There's probably other more general ideas where this can't be fixed (but there's some internal changes to the rules mentioned in other parts of this thread somewhere on (here/reddit/lobsters).
