clang-format vs Fourmolu
clang-format
clang.llvm.orgFourmolu
fourmolu.github.ioSide by side
| Figure | clang-format | Fourmolu |
|---|---|---|
| Price from | — | Free |
| Free plan | — | Yes |
| Free trial | — | — |
| Open source | — | — |
| Web | — | Yes |
| Windows | Yes | Yes |
| macOS | Yes | — |
| Linux | Yes | Yes |
| Plans published | 0 | 1 |
| Spec score · Code Formatting Tools | 7.6 (#20) | 8.3 (#4) |
| Configuration | Formatting styles can be set with command-line options or project-level .clang-format or _clang-format files. | Settings can be provided in a fourmolu.yaml file or as command-line options. |
| Purpose | ClangFormat is a set of tools built on LibFormat for formatting source code, available as a standalone tool and through editor integrations. | Fourmolu formats Haskell source code and is a configurable fork of Ormolu. |
| Selective formatting | The command-line tool can format specified line or byte ranges in a single input file. | Magic comments can disable formatting for selected top-level definitions, and command-line options can format a chosen line region. |
Plans
In their own words
clang-format
clang-format has no write-up on Specifiction yet; its figures are above.
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.