Ruby style guide git pre-commit hook using Rubocop as the style guide checker. Only runs on staged ruby files that have been added and/or modified.

rubocop_pre_commit_hook

#!/usr/bin/env ruby
# frozen_string_literal: true
require 'json'

def files
  @files ||= begin
    `git diff --staged --name-only --cached`.split("\n").reject do |file|
      !File.exists?(file)
    end
  end
end

def rubocop
  @rubocop ||= JSON.parse(
    `bundle exec rubocop --parallel --force-exclusion --format json #{files.join(' ')}`,
    symbolize_names: true
  )
end

def violations
  rubocop[:files].select { |x| x[:offenses].any? }
end

def format_violations
  violations.each do |violation|
    violation[:offenses].each do |offense|
      puts "#{violation[:path]}:#{offense.dig(:location, :line)}:#{offense.dig(:location, :column)} #{offense[:cop_name]} #{offense[:message]}\n"
    end
  end

  puts "\n\n#{rubocop.dig(:summary, :inspected_file_count)} file inspected, #{rubocop.dig(:summary, :offense_count)} offense detected"
end

def success(message)
  puts message
  exit 0
end

def rubocop_autocorrect
  `bundle exec rubocop -A #{files.join(' ')}`
end

def waiting
  index = 0
  chars = %w[| / - \\]
  while @rubocop.nil?
    print "rubocop analyzing ... #{chars[(index += 1) % chars.length]}\r"
    sleep(1)
  end
  puts 'rubocop analyzing ... done'
end

success('no file to check') if files.size.zero?

[].tap do |threads|
  threads << Thread.new { rubocop }
  threads << Thread.new { waiting }
  threads.map(&:join)
end


exit true if violations.empty?

format_violations

# Open input from keyboard usin IO.new(0) normal standard in is closed
fd = IO.sysopen '/dev/tty', 'r'
ios = IO.new(fd, 'r')

print 'Do you want to fix and exit?(Y) '
if ios.gets.chomp == 'Y'
  rubocop_autocorrect
  exit 1
end

print 'Do you want to commit anyway?(Y) '
exit ios.gets.chomp == 'Y'

Add to .git/hooks/pre-commit This will auto correct for you as well. Most of the time is simple things right.

The only thing I change from the original was turning on the auto correct flag. I wanted this to fix the silly things like spaces and other peace that I know Rubocop can do. Something to note however checks your PR because it is an automated tool, but you never know.