[reply from John] Again, thanks! I’ll definitely take a look. Most of the formatter parsers I’ve looked at (e.g. Prettier, Gofmt), will create the AST of the full file, create an IR, and then do the formatting. I’m wondering if each of these steps can be streamed incrementally, and if you can do each operation in parallel. My initial thought is, possibly, but not without some difficulties. For example, Prettier formats line breaks with some awareness of parent and subsequent sibling nodes in its IR).

Looks like yes! topiary is a thing