Fourmolu vs goimports
Fourmolu
fourmolu.github.iogoimports
pkg.go.devSide by side
| Figure | Fourmolu | goimports |
|---|---|---|
| Price from | Free | Free |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | — | — |
| Web | Yes | Yes |
| Windows | Yes | Yes |
| macOS | — | Yes |
| Linux | Yes | Yes |
| Plans published | 1 | 1 |
| Spec score · Code Formatting Tools | 8.3 (#4) | 7.7 (#17) |
| Installation | The project documents installation through GHCup, Cabal, Stack, and dotslash. | The package page gives `go install golang.org/x/tools/cmd/goimports@latest` as the installation command. |
| Purpose | Fourmolu formats Haskell source code and is a configurable fork of Ormolu. | goimports updates Go import lines by adding missing imports and removing unreferenced imports. |
Plans
In their own words
Fourmolu
Fourmolu is a configurable formatter for Haskell source code and a fork of Ormolu. It uses GHC’s parser and aims to keep diffs small, produce idempotent output, and handle large projects. Set formatting options in `fourmolu.yaml` or pass them on the command line. Controls include indentation, line length, import grouping, record layout, Haddock comments, Unicode output, and operator fixities. Fourmolu can find the relevant Cabal file to read default extensions and dependencies that help determine fixities. Magic comments can disable formatting for selected code, and command-line options can target a line region. There is an interactive browser demo with configurable formatting and program options. Installation instructions cover GHCup, Cabal, Stack, and dotslash; editor integration is documented through Haskell Language Server. The project recommends a GitHub Action to keep projects formatted. Its listed current release is v0.21.0.0. CPP handling is experimental and limited to simple cases where conditionals surround top-level declarations. Output always uses LF line endings, which can cause check mode to fail on CRLF files.