Rubocop pre-commit hook

pre-commit.rb

#!/usr/bin/env ruby

# Grab a list of staged changed files
changed_files = `git diff --name-only HEAD`.split("\n")

should_fail, broken_files = false, []

changed_files.each do |file|
  # Run static code analysis on changed file
  output = `rubocop #{file} --format simple`

  # Get exit code of Robocop. Returns a non-zero exit code if it fails.
  exit_code = $?.to_i

  # If Rubocop is not installed, handle gracefully.
  if exit_code == 127
    puts 'It appears that Rubocop is not installed. Please run `bundle install` or `gem install rubocop.`'.yellow
    exit 0
  end

  # Grab all lines of the output.
  lines = output.split("\n")

  # 2nd through -3rd line are the actual errors
  errors = lines[1..-3]

  unless exit_code == 0
    # The commit will fail
    should_fail = true
    broken_files << {
      path: file,
      errors: errors
    }
  end
end

if should_fail
  puts 'Static Code Analysis Failed'.red
  puts '---------------------------'.red

  error_count = 0

  # Produce a nice output for the user.
  broken_files.each do |f|
    puts "  - #{f[:path]}".yellow

    f[:errors].each do |error|
      error_count += 1
      puts "    #{error}".red
    end

    print "\n"
  end

  puts "Detected #{error_count} errors in #{broken_files.count} files.".red

  # Do not allow them to commit.
  exit 1
end