Rake task to sort i18n yaml keys

i18n.rb

namespace :i18n do
  task :sort_keys do
    Dir[Rails.root + "config/locales/*.yml"].each do |fname|
      text = to_yaml(sort_by_key(YAML.load(File.read(fname)))).strip + "\n"
      File.open(fname, "w"){|fd| fd.write(text)}
    end
  end
end

def sort_by_key(m)
  case m
  when Hash
    m.keys.sort.map do |key|
      val = case m[key]
            when Hash
              sort_by_key(m[key])
            when Array
              m[key].map{|v| sort_by_key(v)}
            else
              m[key]
            end
      {key => val}
    end.reduce(&:merge)
  else
    m
  end
end

def to_yaml(val, indent = "")
  nl = indent.size < 4 ? "\n\n" : "\n"
  case val
  when Hash
    val.map do |k,v|
      k = k.inspect if k =~ /\A(yes|no|true|false|on|off|null|\d.*|.*[^\w].*)\Z/i
      "#{nl}#{indent}#{k}: " + to_yaml(v, indent + "  ")
    end.join
  when Array
    val.map do |v|
      "#{nl}#{indent}- " + to_yaml(v, indent + "  ")
    end.join.gsub(/^( *- )\s+/m){$1}
  when String
    if val =~ /\n/
      "|\n#{indent}" + val.split("\n").join("\n#{indent}")
    else
      val.inspect
    end
  when NilClass
    "null"
  when Symbol, Numeric, FalseClass, TrueClass
    val.inspect
  else
    raise ArgumentError, val.inspect
  end.gsub(/\s+$/, "")
end