Integrations

Use Fatou in CI, Git hooks, and other formatting tools. For editor setup, see Editor Setup.

GitHub Actions

Use fatou-action to check formatting and lint Julia code in CI. It installs and caches a prebuilt Fatou binary on GitHub-hosted Linux, macOS, and Windows runners.

Create .github/workflows/fatou.yml:

name: Fatou

on:
  pull_request:
  push:
    branches: [main]

permissions:
  contents: read

jobs:
  fatou:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
      - uses: jolars/fatou-action@v1
        with:
          version: v0.23.0

By default, the action runs fatou format --check and fatou lint from the repository root. It checks .jl files without changing them; formatting differences or lint findings fail the check. Directory walks honor .gitignore and the exclusions in fatou.toml. It uses the same configuration discovery as the CLI.

The action’s @v1 tag selects the action version; the version input selects the Fatou CLI version. Keep the latter aligned with your pre-commit revision and local installation for consistent results. Omitting version selects the latest Fatou release with a binary for the runner.

Set inputs under with to customize the check:

For example, to check only formatting under src/:

- uses: jolars/fatou-action@v1
  with:
    version: v0.23.0
    path: src/
    lint: "false"

Set format: "false" to run only linting. See the action reference for all inputs and outputs.

pre-commit

Run Fatou on staged Julia files with fatou-pre-commit. The hooks install the Fatou binary from PyPI in an environment managed by pre-commit, so you do not need to install Fatou, Rust, or Julia separately.

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

repos:
  - repo: https://github.com/jolars/fatou-pre-commit
    rev: v0.23.0
    hooks:
      - id: fatou-lint
      - id: fatou-format

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

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

On subsequent commits, the hooks run on staged .jl files. fatou-lint reports lint findings, and fatou-format formats files in place. When a hook changes a file, review and stage the changes, then commit again.

To apply safe lint fixes, add --fix to the lint hook. Keep it before the formatter so formatting runs after the rewrites:

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

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

Both hooks pass --force-exclude, so exclude and extend-exclude in your fatou.toml apply even though pre-commit supplies filenames explicitly. See excluding files for details.

The rev selects the Fatou version: v0.23.0 installs Fatou 0.23.0. Run pre-commit autoupdate to update configured hook revisions, then review and commit the changes to .pre-commit-config.yaml.

dprint

Format Julia files alongside other languages with dprint and dprint-plugin-fatou. The plugin bundles Fatou’s formatter as WebAssembly, so you can format .jl files without installing Julia or the Fatou CLI.

Setup

Install dprint. If your project does not yet have a dprint.json, create one with dprint init. Then add Fatou:

dprint config add jolars/fatou

The command adds a versioned plugin URL to the plugins array in your dprint configuration. Commit that configuration so contributors and CI use the same plugin version.

Format the project’s files in place:

dprint fmt

For CI, check formatting without writing changes:

dprint check

The check exits nonzero when files need formatting. Both commands run all configured plugins; Fatou handles .jl files. See the dprint CLI reference for file selection and other options.

Configuration

Add a fatou object to your dprint.json, keeping the plugins array created above. For example, merge in these settings:

{
  "fatou": {
    "lineWidth": 92,
    "indentWidth": 4,
    "lineEnding": "auto"
  }
}

Every setting is optional. Values in fatou override dprint’s global settings:

lineWidth is the target maximum line width, and indentWidth is the number of spaces per indentation level. Fatou always uses spaces; dprint’s global useTabs setting has no effect.

lineEnding: "auto" follows each file’s first line ending, falling back to LF when the file has none. Use lf or crlf to force a particular style. The plugin also accepts native, which resolves to LF in its WebAssembly build, including when dprint runs on Windows.

The plugin reads its settings from dprint’s configuration and does not load fatou.toml. If you also use the Fatou CLI or language server, keep the corresponding [format] settings in sync: line-width, indent-width, and line-ending. See Fatou’s formatting configuration.

dprint controls file discovery through its top-level includes and excludes settings and .gitignore. Put exclusions for this workflow in dprint.json; the plugin does not apply exclusions from fatou.toml. See dprint’s configuration guide.

Updates

The plugin is released independently of the Fatou CLI. To update the plugins listed in your dprint configuration, run:

dprint config update

Review and commit the configuration changes. Updating the Fatou CLI does not update the formatter bundled in the plugin. To get matching output from both, use releases with the same fatou-formatter version and equivalent settings.

The plugin provides formatting. For linting and the full language server, use the Fatou CLI and editor integration.

Using with Panache

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

[formatters]
julia = "fatou"

[linters]
julia = "fatou"

Run panache format document.qmd to format the document and its Julia 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 Fatou linter preset passes --no-config, so it does not load fatou.toml and uses Fatou’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.