Ormolu vs Prettier

Ormolu is a formatter for Haskell source code. It uses GHC’s parser and applies one consistent style, with the aim of keeping diffs small. That style cannot be configured, and the project aims to leave code unchanged when it is formatted again after already meeting the style. Release binaries are available for Linux, macOS, and Windows; installation through cabal or stack is also supported. Ormolu Live provides a browser version. Listed editor integrations cover Emacs, VS Code, and Vim through neoformat or vim-ormolu, and Haskell Language Server has built-in support for Ormolu. For continuous integration, the project recommends the run-ormolu GitHub Action. It reads default language extensions and dependencies from a matching Cabal file;.ormolu files can specify fixity overrides and module re-export instructions. CPP support remains experimental and works only in simple cases where conditionals surround top-level declarations. Ormolu is open source and free, with a listed plan price of free.

Prettier is an open-source code formatter that parses source files and prints them in a consistent style while accounting for line length. Its built-in languages include JavaScript, JSX, Angular, Vue, Flow, TypeScript, CSS, Less, SCSS, HTML, JSON, GraphQL, Markdown, YAML, LWC, and MJML. The command-line interface can write formatted files with --write or check formatting with --check in continuous integration. Listed editor integrations include VS Code, Emacs, Vim, Helix, Sublime Text, JetBrains IDEs, Visual Studio, and Espresso; formatting can run from a shortcut or on save. Prettier has configuration options but keeps them limited. Plugins can add languages and formatting rules, and languages outside the built-in set require a plugin. For ESLint integration, the installation guidance recommends eslint-config-prettier to disable rules that are unnecessary or may conflict. Prettier supports browser and JavaScript API use, along with Linux, macOS, and Windows. The listed plan is free. Commercial support and maintenance are available through the Tidelift Subscription.