ruff VS LibCST

I think I mention this all the time when this comes up, but I learned the most 'best practices' through using ruff.

https://docs.astral.sh/ruff/

I just installed and enabled all the rules by setting

Ruff is a Python linter that helps to identify and remove code smells. Over 700 built-in rules: Ruff includes native re-implementations of popular Flake8 plugins, like flake8-bugbear. And also built-in caching to avoid re-analyzing unchanged files.

Because the Python's "ast" modules is too slow, and lacks proper "format" feature (it has unparse but it removes comments, and forgets the current style completely). I use "ruff" a lot (https://github.com/astral-sh/ruff) which is in Rust. But I want to be able to implement fast custom linters in Go (linters that ruff / fixit lack, and Python linters lack or are too slow).

I think it’s interesting that rye uses ruff (https://github.com/astral-sh/ruff) for linting and formatting. That’s the right call, and it’s also correct to bundle that in for an integrated dev experience.

I had to guess, that’s the path that the Astral team would take as well - expand ruff’s capabilities so it can do everything a Python developer needs. So the vision that Armin is describing here might be achieved by ruff eventually. They’d have an advantage that they’re not a single person maintenance team, but the disadvantage of needing to show a return to their investors.

Adding more weight to ease of setup and configurability, the choice came down on flake8. It is easy to integrate, since its also available through pip and let’s you configure which standards you want to omit by simply stating them as a list via the --ignore switch. Moving to ruff appears quite smooth, so future updates may do so.

I confess I stole the pip recipe from Charlie :D

https://github.com/astral-sh/ruff/blob/main/.github/workflow...

Ruff is an emerging tool in the Python ecosystem that describes itself as "an extremely fast Python linter and code formatter, written in Rust".

LibCST: Seems to only show in terminal.

While you can do this using ANTLR or any other lexing/parsing tool, it's honestly a bit of a pain. Whitespace and comments can go almost anywhere, even in the middle of expressions, so the grammar ends up becoming fairly messy. So, I'd recommend using a library that handles this for you, if at all possible. For example, if I wanted to code-mod Python I'd prob just use the LibCST library.

I recommend https://github.com/Instagram/LibCST (which is currently implementing rust bindings)

I've been roughly copying some of the logic from the LibCST project. This struct in particular- https://github.com/Instagram/LibCST/blob/main/native/libcst/src/tokenizer/text_position/char_width.rs does a good job of normalizing the line endings of a str. The long way around you could mimic this construct, transform the str to normalized line endings, and then split on "\n" or make a somewhat more complicated transformer which turns a large str into a Vec (or Vec).

I myself am working on upgrading LibCST's parser engine to support the new syntax, and then am hoping we can rewrite Black's formatting rules in terms of LibCST's API. That's not a small amount of work, which is why we can't confidently say that's going to be the way forward.

Never used it but it appears that Facebook/Instagram have a format preserving CST library for Python: https://github.com/Instagram/LibCST