Add rome_formatter fork as ruff_formatter

[charliermarsh]

The Ruff autoformatter is going to be based on an intermediate representation (IR) formatted via Wadler's algorithm. This is architecturally similar to Rome, Prettier, Skip, and others.

This PR adds a fork of the rome_formatter crate from Rome, 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.

[charliermarsh]

\cc @MichaReiser

[MichaReiser]

LGTM

Some things to consider:

• Should we re-license the crates
• Can we document the use of prior work in an acknowledgment section (pylint, Rome, Prettier...)
• It's probably worth unifying the logging infrastructure. Rome uses tracing whereas Ruff uses some other crates.

[MichaReiser]

You may want to change the authors to Ruff.

[charliermarsh]

I wasn't certain what the "right" pattern was here. I noticed (e.g.) that rome_rowan has authors = ["Aleksey Kladov <aleksey.kladov@gmail.com>"].

[charliermarsh]

Should we re-license the crates

Ah yeah. How should this work? We already include a bunch of licenses in our LICENSE file -- could we add the existing licenses there, and then cover these forks under the project's MIT license?

Can we document the use of prior work in an acknowledgment section (pylint, Rome, Prettier...)

Good idea -- I'll do this in a separate PR.

It's probably worth unifying the logging infrastructure. Rome uses tracing whereas Ruff uses some other crates.

Also a good idea -- I'll also do this in a separate PR.

[MichaReiser]

Ah yeah. How should this work? We already include a bunch of licenses in our LICENSE file -- could we add the existing licenses there, and then cover these forks under the project's MIT license?

I'm not really familiar with re-licensing but adding another copyright seems to work (if that's even something we want)

https://gist.github.com/fbaierl/1d740a7925a6e0e608824eb27a429370