Run Fourmolu

Version updated for https://github.com/haskell-actions/run-fourmolu to version v12.

• This action is used across all versions by 53 repositories.

Action Type

This is a Node action using Node version 24.

Go to the GitHub Marketplace to find the latest changes.

Action Summary

The run-fourmolu GitHub Action ensures consistent code formatting for Haskell projects by automatically checking if Haskell source files adhere to the formatting standards defined by Fourmolu. It identifies unformatted files, provides a diff highlighting discrepancies, and can be configured to target specific files or directories. This action streamlines the code formatting process in CI workflows, helping teams maintain clean and consistent codebases.

What’s Changed

Upgrade from Node.js 20 to Node.js 24. This is a required upgrade since GitHub Actions is deprecating Node.js 20. Runners will default to Node.js 24 starting June 2, 2026, and Node.js 20 will be fully removed in fall 2026. Older versions of run-fourmolu (v11 and below) will stop working after this date.

Implemented in #32.

• haskell-actions
• GitHub Actions