WARNING! This is a work in progress. It's not ready for general use yet.

Nit

Nit is a secure Python-free alternative to pre-commit. It has the following advantages over pre-commit.

• It's not written in Python:
  • Way faster.
  • Much easier to distribute (single statically linked binary).
  • Avoids the endless installation issues that plague Python.
• Linters are WASI plugins:
  • Naturally cross-platform.
  • Sandboxed; they can only read and write your code. No network access.
  • Many languages are supported.
  • Caching plugins (e.g. in Docker images) is much easier.
  • In future (not implemented yet), the filesystem access can be virtualised so it actually reads Git blobs. Pre-commit lints the wrong files in some cases since it can only lint actual on-disk files. This will also allow a --no-fix flag without requiring explicit linter support.

Probably the biggest reasons I wrote this are the Python issues (I have spend a lot of time with numerous colleagues figuring out why Python is barfing on pre-commit), and the safety (I don't really want to give random people complete access to my and my colleagues' machines just to remove tabs).

There are some limitations too:

• Since linters can't run Git some lints are a bit awkward, e.g.
  • Lint to ban submodules
  • Lint to check if files are executable (needs Git because this isn't exposed to the filesystem on Windows)
• WASM is a fair bit slower than native still.
• WASI is still very immature and compiling linters for WASI is quite a pain.

Installation

Download the latest release from the releases page and put it in your PATH.

Usage

This is similar to pre-commit. Create a .nit.json5 file (.jsonc and .json are also accepted) in the root of your repository. Comments and trailing commas are allowed. Here's an example:

{
    linters: [
        {
            name: "Ruff (Python format/lint)",
            location: {
                remote: {
                    url: "https://github.com/Timmmm/ruff/releases/download/0.0.1/ruff.wasm",
                    hash: "becf10f9e95dbb08d66b01a662c6041abb53aac64f3af669e81b6abd24b7b015",
                },
            },
        },
    ],
    include: {
        bool: true,
    },
}

Then run nit run --all in the root of your repository. It will lint all the files in the repository. If you run nit run instead it will only lint the files that have changed, as determined by git diff.

To install as a git hook, run nit install. For compatibility with pre-commit this will install as a pre-commit hook by default, though I find pre-push way less annoying so I would recommend nit install --hook-type pre-push instead.

Linters

Linters are WASI modules, plus a special custom section containing some metadata about how to run them.

To compile e.g. Ruff to WASI.

rustup toolchain install nightly
rustup +nightly target add wasm32-wasip2

git clone -b user/timh/wasi https://github.com/timmmm/ruff.git
cd ruff

rustup override set nightly

cargo build --release --target wasm32-wasip2

nit set-metadata --metadata metadata.json target\wasm32-wasip2\release\ruff.wasm

This uses a branch because WASI is quite immature and I had to fix some stuff.

To compile rustfmt:

git clone https://github.com/rust-lang/rustfmt.git
cd rustfmt

rustup toolchain install nightly
rustup target add wasm32-wasip2

export CFG_RELEASE=1.85.1-nightly
export CFG_RELEASE_CHANNEL=nightly
export RUSTC_BOOTSTRAP=0

cargo build --release --target wasm32-wasip2

Use in CI

If you are using a custom Docker image for CI, you can bake all of the linters into it so they won't be downloaded each time it runs. Simply run nit fetch --config <config.json> in your Dockerfile.

Environment Variables

Nit respects the following environment variables:

• NIT_CACHE_DIR: If set, the location to store downloaded linters.