statix VS pom

As others have mentioned, there are a couple of LSP implementations. There's also statix for basic static analysis, as well as a few formatters, including nixpkgs-fmt and alejandra.

I use the author's pretty error rendering crate: ariadne, in statix, and it is a delight. Comfy API, loads of customization opts, and very pretty.

pom

Maybe a parser combinator library is not what you want? One alternative might be writing an expression parser without a library at all: https://matklad.github.io/2020/04/13/simple-but-powerful-pratt-parsing.html (Depending on the grammar you are parsing a Pratt parser might actually be a good fit!) A PEG might also be more suitable for your use case, like pom.

I saw the performance comparison against pom, pom is unfortunately quite slow compared to an handwritten parser as it boxes most (all?) parsers so you may want to compare against a handwritten parser, or at least something in the same ballpark (for reference, combine's json benchmark on the same data is about 6x faster with "good errors", when optimized to work on &str-like input it is about 12x faster, nom or a hand written parser may be another 10-20% faster than that, if I remember correctly.) From a brief skim of the code, I don't see anything that would hinder it from at least closing that gap however.

Everyone on this sub seems to be using nom. In my experience I find pom to be intuitive and have to write less code. Maybe it's just me I'm having a hard time understanding nom which has a lot of function calls rather than less.If you compare both the json examples on both projects, the pom example is a lot clearer to read and a lot shorter.