Pre commit hooks

[aciceri]

Several people working on different projects asked for help to have pre-commit hooks in their projects, in my opinion it would make sense centralize this here.

pre-commit-hooks.nix seems to be the de facto standard for this but I agree with @L-as that it would be bloated for our purposes (we already have our linter/formatter derivations and we don't want to fetch a different ghc only to build the formatter executable).

I see two possible solutions:

• we implement a barebone custom solution aping pre-commit-hooks.nix (the "core" of pre-commit-hooks.nix should be quite trivial, if its repo "seems big" is because of the many supported languages)
• we use pre-commit-hooks.nix adding our own custom hooks that leverages on our ,format and ,lint scripts (overriding default hooks for haskell possibly)

By the way I would make this optional.

cc @bladyjoker @maciej-bendkowski @brainrake

[bladyjoker]

Hey @aciceri good stuff!

Check out https://github.com/mlabs-haskell/protobufs.nix/blob/main/src/pre-commit-hooks.nix for how to add a new hook, and https://github.com/mlabs-haskell/protobufs.nix/blob/main/pre-commit-check.nix#L16 on how to provide your own 'tools' (primarily fourmolu, but perhaps works with ghc as well).

Note that each repo comes with their own needs

  hooks = {
    nixpkgs-fmt.enable = true;
    nix-linter.enable = true;
    cabal-fmt.enable = true;
    fourmolu.enable = true;
    shellcheck.enable = true;
    hlint.enable = true;
    typos.enable = true;
    markdownlint.enable = true;
  } // protoHooks;

For the most part, mlabs-tooling can assume some common checks (nix, cabal, haskell), but we should have the ability to configure (remove and add hooks) as desired.

Additionally, most of these code quality tools have their own configuration files, would be nice to have those in a reusable but also configurable mode. Example config files: https://github.com/mlabs-haskell/protobufs.nix/blob/main/.markdownlint.yaml and https://github.com/mlabs-haskell/protobufs.nix/blob/main/_typos.toml

Hope that helps.

[aciceri]

@bladyjoker Thank you! We'll definitely check these links when we'll work on this (don't know how soon).

[L-as]

We should just allow overriding the script added to the pre-commit hook.