Biome vs Fourmolu

Biome is a toolchain for maintaining the health of web projects. It formats JavaScript, TypeScript, JSX, TSX, JSON, HTML, CSS, and GraphQL, and provides lint rules for JavaScript, TypeScript, JSX, CSS, and GraphQL. Linting can report diagnostics and apply safe fixes. Its check command can format files, lint them, and organize imports in one run. Biome is distributed as a standalone executable, so it does not require Node.js. Installation instructions cover npm, pnpm, bun, deno, and yarn. First-party editor extensions are available for VS Code, IntelliJ, and Zed; community extensions include Vim, Neovim, and Sublime Text. The getting-started guide links to CI integrations for GitHub Actions and GitLab CI. Biome describes itself as open source and lists MIT or Apache 2.0 licensing. The open-source toolchain is free. Contributors may offer commercial support, but requests depend on their availability.

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.