Add support for linters

[zimbatm]

Unlike formatters, multiple linters can be executed for a single file. Linters sometimes also write back fixes to the file.

The config format has rooms for a [linters.<name>] section.

This needs to be specced-out a bit more.

[zimbatm]

See also https://github.com/reviewdog/reviewdog

[9999years]

I would like this to work around astral-sh/ruff#8232 by running ruff check --fix && ruff format.

[zimbatm]

Something like this should work:

[formatter.ruff]
command = "sh"
options = ["-c", "ruff check \"$@\" && ruff format \"$@\"", "--"]
includes = ["*.py", "*.pyi"]

[evolutics]

First: thanks for this time-saving project!

What's the maintainers' opinion about linters in treefmt-nix?

The docs seem to speak about formatters only, not linters. Also, the name "treefmt" suggests that this is a project about code formatting.

Currently, treefmt-nix offers some linters such as ShellCheck, jsonnet-lint, etc.

Just asking to see what the chances would be for PRs to support more linters like hadolint or Pylint.

Surely, the distinction between formatter and linter isn't always that clear. Some linters have an additional fix mode that may change things, akin to formatting. Technically, most linters in check mode return a non-zero exit status if they discover lints, whereas most formatters exit with status zero even if they changed something (Rufo being an exception unless invoked with --simple-exit).

[sellout]

This would be very helpful.

I recently changed my treefmt-nix config to use treefmt v2 instead of v1 in order to avoid #153, but now I find that v2 errors with “path '…' matched multiple formatters/pipelines [hlint ormolu]” on all my Haskell code.

I’m currently waffling on whether I should go back to v1 for Haskell projects (which skips formatting many things) or disable hlint.

[brianmcgee]

@sellout which version of v2 are you using?

That error message is old, in fact I don't think that's even in 2.0.1: ce14ee8 Sounds like you're using a 2.0.0 rc release.

The latest is 2.0.5.

[sellout]

@sellout which version of v2 are you using?

That error message is old, in fact I don't think that's even in 2.0.1: ce14ee8 Sounds like you're using a 2.0.0 rc release.

Ah, whoops – it’s 2.0.0-rc2, from Nixpkgs 24.05 (the current release). I usually check these things, but assumed this issue was specifically about the problem of having multiple formatters.

Thanks – I’ll overlay a newer one.

[brianmcgee]

@sellout multiple formatters on the same files are not a problem anymore: https://treefmt.com/configure#same-file-multiple-formatters

[sellout]

@sellout multiple formatters on the same files are not a problem anymore: https://treefmt.com/configure#same-file-multiple-formatters

Thanks – I pulled 2.0.5 from nixpkgs-unstable and the formatting is working better than ever. No notes.