Compares two YAML files and shows which keys are "missing" and which keys are "extras"

compare.rb

require 'yaml'

class Hash
  def fully_qualified_keys
     map { |k,v|
       v.fully_qualified_keys.map{ |a| "#{k}.#{a}" } rescue k.to_s
     }.flatten
  end
end

def yaml_hash_for(file)
  YAML.load(File.open(File.expand_path file))
end

h1 = yaml_hash_for ARGV[0]
h2 = yaml_hash_for ARGV[1]

def compare(expected, actual)
  expected_keys = expected.fully_qualified_keys
  actual_keys = actual.fully_qualified_keys

  missing    = expected_keys - actual_keys
  extraneous = actual_keys - expected_keys

  if missing.any?
    puts "Expected these keys, but didn't find them:"
    missing.each { |key| puts "  - #{key}" }
  end
  if extraneous.any?
    puts "Found these keys, but didn't expect them:"
    extraneous.each { |key| puts "  + #{key}" }
  end
end

compare(h1, h2)