Black vs Ormolu

Black is a free, MIT-licensed formatter for Python code that follows PEP 8. It reformats whole files in place and uses a default line length of 88 characters. Its limited style choices are intended to keep code consistent across projects; indentation style cannot be configured. After formatting, Black checks whether the abstract syntax tree remains effectively equivalent and raises an error if the check fails. Install it with pip; it requires Python 3.10 or newer. The documentation lists editor integrations including Emacs, PyCharm, IntelliJ IDEA, Vim, Neovim, Visual Studio Code and Sublime Text, as well as GitHub Actions and doctest workflows. Notebook formatting is available with the jupyter extra, though Black skips cells containing certain magics or invalid syntax. It also includes blackd, an HTTP server that binds to localhost by default. Black is primarily a command-line tool and does not provide a Python interface. Stable releases preserve formatting within the same calendar year when the options match.

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.