Arity

Arity is a language server, formatter, and linter for the R programming language, built in Rust on a lossless, incremental parser. It provides a fast, deterministic development experience that integrates with popular code editors and IDEs.

• Formatter: deterministic, rule-based formatting toward the tidyverse style guide, with idempotent output and roxygen support.
• Linter: correctness, readability, and performance rules, many with safe autofixes.
• Language server: formatting, diagnostics with quick fixes, hover, completion, signature help, go-to-definition and references, rename, document and workspace symbols, semantic tokens, folding, and call hierarchy.

Installation

Arity is available from several sources:

• crates.io: cargo install arity
• Homebrew: brew install jolars/tap/arity
• npm: npm install -g arity-cli (bundles a prebuilt binary)
• PyPI: uv tool install arity/pipx install arity
• Aqua: aqua install jolars/arity
• Prebuilt binaries: from the releases page
• VS Code/Open VSX: the Arity extension (also works in Positron)
• Arch Linux: pacman -S arity-bin (or arity) (from the AUR: arity-bin, arity)
• NixOS: the arity package is available in the Nixpkgs repository

Install script

The install scripts are fetched from the latest release and download the Arity release asset for your platform, verifying its checksum and installing to a user-local directory by default. If you prefer, download and inspect the script before running it.

For macOS and Linux:

curl --proto '=https' --tlsv1.2 -LsSf \
    https://github.com/jolars/arity/releases/latest/download/arity-installer.sh | sh

For Windows PowerShell:

powershell -NoProfile -ExecutionPolicy Bypass -Command "irm https://github.com/jolars/arity/releases/latest/download/arity-installer.ps1 | iex"

Set ARITY_INSTALL_DIR to change the destination, ARITY_TAG to pin a version, ARITY_LIBC (gnu or musl) to override the detected libc on Linux, and ARITY_VERIFY_CHECKSUM=false to skip checksum verification.

Formatter

To format your code, you can use:

• arity format [file]
• arity format --verify [file]
• arity format --check <path> [<path> ...]

Linter

To lint your code, you can use:

• arity lint <path> [<path> ...]

arity lint reads from stdin when given no paths, and exits non-zero when it reports any findings.

Configuration

Arity reads an optional arity.toml, discovered by walking up from each file's directory to the repository root. Run arity init to scaffold a commented starter file. See the configuration reference for every key.

Editor integration

arity lsp starts a stdio-based language server offering formatting, diagnostics with quick fixes, hover, completion, signature help, go-to-definition and references, rename, document and workspace symbols, semantic tokens, folding, and call hierarchy.

The Arity extension for VS Code/Open VSX (and Positron) bundles the binary and starts the server automatically. For Neovim, Helix, and other editors, see the editor setup guide.

Pre-commit hook

arity-pre-commit provides pre-commit hooks for linting and formatting. It installs a prebuilt binary wheel from PyPI, so no Rust toolchain or R installation is required:

repos:
  - repo: https://github.com/jolars/arity-pre-commit
    # arity version
    rev: v0.13.0
    hooks:
      # Lint .R files
      - id: arity-lint
      # Format the same files in place
      - id: arity-format

GitHub Actions

arity-action installs arity and runs format and lint checks in CI:

jobs:
  arity:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
      - uses: jolars/arity-action@v1

Crates

The parsing and formatting engines are published as standalone crates for use in other tools: arity-parser (lossless CST parser, typed AST wrappers, incremental reparser) and arity-formatter (the formatter, with optional serde/schemars support for embedders). Both are versioned independently of the CLI.

Acknowledgements

The core architecture of Arity is entirely based on rust-analyzer, using salsa for incremental computation and rowan for lossless syntax trees. Arity also owes a great debt to air, on which it is heavily inspired and from which it has borrowed tests, rules, and formatting style. It is also inspired by jarl and has borrowed rules from it as well as some of its architecture.

Documentation

Full documentation lives at arity.cc:

• Getting started
• Editor setup
• Configuration
• CLI reference
• Lint rules