Adds RuboCop to a project, one commit per cop

rubocoper

#!/usr/bin/env ruby

require 'open3'

#
# Adds RuboCop to a project, one cop per commit
#
class RuboCoper
  def run
    autocorrect_all

    autocorrect_leftovers

    generate_todo_config
  end

  private

  #
  # Generates an offense free _todo_ configuration
  #
  def generate_todo_config
    puts 'Generating todo config...'
    run_cmd('bin/rubocop --auto-gen-config')

    File.open('.rubocop.yml', 'a') do |f|
      f.puts "\ninherit_from: .rubocop_todo.yml"
    end

    commit('Add RuboCop offense free configuration')
  end

  #
  # Some cop autocorrections introduce offenses that are expected to be
  # fixed by other autocorrections. So do a final pass to fix those.
  #
  def autocorrect_leftovers
    puts 'Autocorrecting leftover offenses...'
    run_cmd('bin/rubocop --auto-correct')
    commit('Remove leftover RuboCop offenses')
  end

  #
  # Iterate through each offense, try to autocorrect it and add a commit if
  # something was corrected.
  #
  def autocorrect_all
    run_cmd('bin/rubocop --format=offenses').split("\n").each do |line|
      match_result = line.match(%r{\d+\s+(?<cop_name>\w+/\w+)})
      next unless match_result

      puts "Autocorrecting #{match_result[:cop_name]}..."
      autocorrect(match_result[:cop_name])
    end
  end

  #
  # Autocorrects a single offense
  #
  def autocorrect(cop_name)
    run_cmd("bin/rubocop --only #{cop_name} --auto-correct")
    commit("Fix #{cop_name} offenses")
  end

  #
  # Runs a given command and rises if it fails
  #
  def run_cmd(command)
    out, err, status = Open3.capture3(command)

    print(err) unless status.success?

    out
  end

  #
  # Commits changes in current working tree with given message
  #
  def commit(message)
    run_cmd('git add .')
    run_cmd("git commit -m '#{message}'")
  end
end

RuboCoper.new.run