Ruby 1.9: how to properly upcase/downcase multibyte strings?

Question

So matz took the questionable decision to keep upcase and downcase limited to /[A-Z]/i in ruby 1.9.1.

ActiveSupport::Multibyte has long had great i18n case jiggering in ruby 1.8.x via String#mb_chars.

However, when tried under ruby 1.9.1, it doesn't seem to work. Here's a simple test script I wrote, along with the output I'm getting:

$ cat test.rb
# encoding: UTF-8

puts("@ #{RUBY_VERSION} " + (__ENCODING__ rescue $KCODE).to_s)
sd, su = "Iñtërnâtiônàlizætiøn", "IÑTËRNÂTIÔNÀLIZÆTIØN"
def ps(u, d, k); puts "%-30s:  %24s / %-24s" % [k, u, d] end
ps sd.upcase, su.downcase, "Plain ruby"

require 'rubygems'; require 'active_support'
ps sd.upcase, su.downcase, "With active_support"
ps sd.mb_chars.upcase.to_s, su.mb_chars.downcase.to_s, "With active_support mb_chars"

$ ruby -KU test.rb
@ 1.8.7 UTF8
Plain ruby                    :  IñTëRNâTIôNàLIZæTIøN / iÑtËrnÂtiÔnÀlizÆtiØn
With active_support           :  IñTëRNâTIôNàLIZæTIøN / iÑtËrnÂtiÔnÀlizÆtiØn
With active_support mb_chars  :  IÑTËRNÂTIÔNÀLIZÆTIØN / iñtërnâtiônàlizætiøn

$ ruby1.9 test.rb
@ 1.9.1 UTF-8
Plain ruby                    :      IñTëRNâTIôNàLIZæTIøN / iÑtËrnÂtiÔnÀlizÆtiØn
With active_support           :      IñTëRNâTIôNàLIZæTIøN / iÑtËrnÂtiÔnÀlizÆtiØn
With active_support mb_chars  :      IñTëRNâTIôNàLIZæTIøN / iÑtËrnÂtiÔnÀlizÆtiØn

So, how do I get internationalized upcase and downcase with ruby 1.9.1?

update

I should add that I also tested with ActiveSupport from the current master, 2-3-* and 3-0-unstable rails branches at GitHub. Same results.

Answer 1

Case conversion is locale dependent and doesn't always round-trip, which is why Ruby 1.9 doesn't cover it (see here and here)

The unicode-util gem should address your needs.