Adds titleize/titlecase to AS::Multibyte::Chars

[#2794 state:resolved]

Signed-off-by: José Valim <jose.valim@gmail.com>

activesupport/lib/active_support/multibyte/chars.rb

@@ -371,6 +371,16 @@ def capitalize
         (slice(0) || chars('')).upcase + (slice(1..-1) || chars('')).downcase
       end
 
+      # Capitalizes the first letter of every word, when possible.
+      #
+      # Example:
+      #   "ÉL QUE SE ENTERÓ".mb_chars.titleize    # => "Él Que Se Enteró"
+      #   "日本語".mb_chars.titleize                 # => "日本語"
+      def titleize
+        chars(downcase.to_s.gsub(/\b('?[\S])/u) { Unicode.apply_mapping $1, :uppercase_mapping })
+      end
+      alias_method :titlecase, :titleize
+
       # Returns the KC normalization of the string by default. NFKC is considered the best normalization form for
       # passing strings to databases and validations.
       #

activesupport/test/multibyte_chars_test.rb

@@ -443,6 +443,11 @@ def test_capitalize_should_work_on_ascii_characters
     assert_equal 'Abc', 'abc'.mb_chars.capitalize
   end
 
+  def test_titleize_should_work_on_ascii_characters
+    assert_equal '', ''.mb_chars.titleize
+    assert_equal 'Abc Abc', 'abc abc'.mb_chars.titleize
+  end
+
   def test_respond_to_knows_which_methods_the_proxy_responds_to
     assert ''.mb_chars.respond_to?(:slice) # Defined on Chars
     assert ''.mb_chars.respond_to?(:capitalize!) # Defined on Chars
@@ -480,6 +485,15 @@ def test_capitalize_should_be_unicode_aware
     end
   end
 
+  def test_titleize_should_be_unicode_aware
+    assert_equal "Él Que Se Enteró", chars("ÉL QUE SE ENTERÓ").titleize
+    assert_equal "Абвг Абвг", chars("аБвг аБвг").titleize
+  end
+
+  def test_titleize_should_not_affect_characters_that_do_not_case_fold
+    assert_equal "日本語", chars("日本語").titleize
+  end
+
   def test_limit_should_not_break_on_blank_strings
     example = chars('')
     assert_equal example, example.limit(0)