The Ruff autoformatter is going to be based on an intermediate representation (IR) formatted via [Wadler's algorithm](https://homepages.inf.ed.ac.uk/wadler/papers/prettier/prettier.pdf). This is architecturally similar to [Rome](https://github.com/rome/tools), Prettier, [Skip](https://github.com/skiplang/skip/blob/master/src/tools/printer/printer.sk), and others.
This PR adds a fork of the `rome_formatter` crate from [Rome](https://github.com/rome/tools), renamed here to `ruff_formatter`, which provides generic definitions for a formatter IR as well as a generic IR printer. (We've also pulled in `rome_rowan`, `rome_text_size`, and `rome_text_edit`, though some of these will be removed in future PRs.)
Why fork? `rome_formatter` contains code that's specific to Rome's AST representation (e.g., it relies on a fork of rust-analyzer's `rowan`), and we'll likely want to support different abstractions and formatting capabilities (there are already a few changes coming in future PRs). Once we've dropped `ruff_rowan` and trimmed down `ruff_formatter` to the code we currently need, it's also not a huge surface area to maintain and update.
Micha Reiser
Jonathan Plasse
Charlie Marsh