Fourmolu vs Spotless

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.

Spotless formats source code and can check files for formatting violations or apply fixes. It supports languages and formats including Java, Kotlin, JavaScript, Python, SQL, YAML, and Markdown, with formatter options such as Google Java Format, ktlint, Prettier, ESLint, Black, and ScalaFmt. The project integrates with Gradle and Maven and links to an external SBT integration. Its README links to VS Code and IntelliJ integrations. Spotless lists automatic idempotency and encoding safeguards for Gradle, Maven, and SBT. Git-based features include ratcheting from a Git reference for Gradle and Maven, and Git-defined line endings for all three build tools. Some capabilities, including ratcheting and fast incremental formatting, are unavailable in SBT. The repository identifies the license as Apache-2.0. Spotless is available for Linux, macOS, and Windows. DiffPlug directs questions to its forum and lists a technical support contact; security disclosures can be sent to [email protected]. Its plan listing includes a free plan at free, billed free forever with no registration required, and also lists a free trial.