A danger plugin for the Haskell code formatter ormolu


$ gem install danger-ormolu


Be sure to have ormolu and diff in your PATH, include it in your Gemfile:

# frozen_string_literal: true

source "https://rubygems.org"

git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }

# gem "rails"
gem 'danger'
gem 'danger-ormolu'

Finally use this line in your Dangerfile:

# get all affected files by the changes in the current diff
affected_files = git.added_files + git.modified_files

# limit files to .hs files
haskell_files = affected_files.select { |file| file.end_with?('.hs') }

ormolu.check haskell_files
Methods and attributes from this plugin are available in
your `Dangerfile` under the `ormolu` namespace.


  1. Clone this repo
  2. Run bundle install to setup dependencies.
  3. Run bundle exec rake spec to run the tests.
  4. Use bundle exec guard to automatically have tests run as you make changes.
  5. Make your changes.