Integrations

Use Arity in CI, Git hooks, and other formatting tools.

For editor and language-server setup, see Editor setup instead.

GitHub Actions

arity-action installs arity and runs the format and lint checks in CI. Create .github/workflows/arity.yml:

name: Arity

on:
  pull_request:
  push:
    branches: [main]

permissions:
  contents: read

jobs:
  arity:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
      - uses: jolars/arity-action@v1
        with:
          version: v0.25.0

By default this runs both arity format --check and arity lint over the whole repository without changing files. It checks R files and package-root DESCRIPTION files using the CLI's configuration discovery. Directory walks honor .gitignore and the exclusions in arity.toml. Formatting differences or lint findings fail the check.

The @v1 tag selects the action version; version selects the Arity CLI release. Keep the latter aligned with your local installation and pre-commit revision. Omitting it selects latest. Common inputs:

Input	Default	Description
path	.	File or directory to check
version	latest	Version to install (latest or vX.Y.Z)
format	true	Run arity format --check
lint	true	Run arity lint
config	(none)	Path to an arity.toml to use
verify-checksum	true	Verify the downloaded asset against its published hash

It also exposes the installed version as the version output. To run only one of the two checks, turn the other off:

- uses: jolars/arity-action@v1
  with:
    version: v0.25.0
    path: R
    lint: "false"

Set format: "false" to run only linting. See the action reference for the inputs and outputs supported by @v1.

pre-commit

arity-pre-commit provides pre-commit hooks. They install a prebuilt binary wheel from PyPI, so no separate Arity or Rust installation is needed.

Install pre-commit, then add this entry to .pre-commit-config.yaml:

repos:
  - repo: https://github.com/jolars/arity-pre-commit
    rev: v0.25.0
    hooks:
      - id: arity-lint
      - id: arity-format

Install the Git hook and run it once over all tracked files:

pre-commit install
pre-commit run --all-files

On subsequent commits, arity-lint reports findings for staged .r and .R files. arity-format formats those files and staged DESCRIPTION files in place. The lint hook does not select DESCRIPTION files by default, although the CLI supports them. When a hook changes a file, review and stage the changes, then commit again.

To apply safe fixes, add --fix to the lint hook and keep it before formatting:

hooks:
  - id: arity-lint
    args: [--fix]
  - id: arity-format

To check formatting without changing files, add args: [--check] to arity-format.

Both hooks run with --force-exclude. pre-commit passes staged files as explicit arguments, and files named explicitly are normally always processed; the flag applies the exclude patterns from your arity.toml to them anyway, so a staged file you have excluded stays excluded. See Configuration for those patterns.

The rev selects the Arity release: v0.25.0 installs Arity 0.25.0. Run pre-commit autoupdate to update hook revisions, then review and commit the changes to .pre-commit-config.yaml.

dprint

Format R files alongside other languages with dprint and dprint-plugin-arity. The plugin bundles Arity's formatter as WebAssembly, so no Arity CLI or R installation is needed.

Install dprint. If your project has no dprint.json, create one with dprint init, then add Arity:

dprint config add jolars/arity

Commit the versioned, checksummed plugin URL that the command adds to dprint.json. Run dprint fmt to format files in place or dprint check to check without changing files. The check fails when files need formatting. The plugin handles .r and .R files; it provides formatting rather than linting.

Configure it under the arity key:

Key	Values	Default
lineWidth	integer	dprint global, else 80
indentWidth	integer	dprint global, else 2
lineEnding	auto, lf, crlf, native	from global newLineKind
roxygen	boolean	true
roxygenMarkdown	boolean	false

These correspond to the formatting settings. Set roxygen to false to preserve roxygen comment layout while formatting the surrounding R code.

The plugin reads its configuration from dprint.json and does not load arity.toml. Use dprint's top-level includes and excludes for file selection; Arity's TOML exclusions do not apply. dprint also respects .gitignore. See dprint's configuration guide.

The Arity CLI discovers whether roxygen comments use Markdown by reading the package's DESCRIPTION and man/roxygen/meta.R. The plugin cannot read those files. So a package whose DESCRIPTION sets Roxygen: list(markdown = TRUE) needs roxygenMarkdown set explicitly:

{
  "arity": { "roxygenMarkdown": true }
}

Per-block @md and @noMd tags still take precedence over that default, exactly as they do in the CLI.

The plugin is released independently of the CLI. Run dprint config update, then review and commit the configuration changes. Matching CLI output requires the same arity-formatter version, equivalent settings, and an explicit roxygenMarkdown setting when the CLI derives it from package files.

Using with Panache

Panache can format and lint R code blocks inside Markdown, Quarto, and R Markdown documents. Install both CLIs on your PATH, then add this to the document project's panache.toml:

[formatters]
r = "arity"

[linters]
r = "arity"

Run panache format document.qmd to format the document and its R blocks, or panache lint document.qmd to report findings without changing files. The linter also runs through Panache's language server. To apply safe fixes before formatting, run panache lint --fix document.qmd, then format the document.

Panache's Arity linter preset passes --no-config, so it does not load arity.toml and uses Arity's default lint configuration. The formatter preset runs separately and retains its CLI configuration behavior. See Panache's formatter preset, linter preset, and external-tool configuration.

mise-en-place

Use mise or Aqua to install and pin the Arity CLI for a project.