Correctly handle phrases in singularize/pluralize.

Currently, the inflector is not set up correctly to handle phrases
(multi-word strings) as input. This ocasionally works right now, but it
is more or less a coincidence. Since Rails internally depend on this
singularize/pluraize being able to handle phrases (see tableize), this
commit fixes the bug and correctly handle phrases in singularize and
pluralize. The following should work as expected after this patch:

   'MyClass'.pluralize # => 'MyClasses'
   'some-slug'.pluralize # => 'some-slugs'
   'saw_fish'.pluralize # => 'saw_fish'
   'optical mouse'.pluralize # => 'optical mice'
   'funky jeans'.singularize # => 'funky jeans'

See rails#7134 for discussions.

activesupport/lib/active_support/inflector/methods.rb

@@ -312,12 +312,28 @@ def const_regexp(camel_cased_word) #:nodoc:
     #  apply_inflections("posts", inflections.singulars) # => "post"
     def apply_inflections(word, rules)
       result = word.to_s.dup
+      prefix, last_word = split_phrase(result)
 
-      if word.empty? || inflections.uncountables.include?(result.downcase[/[a-z0-9]+\Z/])
+      if word.empty? || inflections.uncountables.include?(last_word.downcase)
         result
       else
-        rules.each { |(rule, replacement)| break if result.sub!(rule, replacement) }
-        result
+        rules.each { |(rule, replacement)| break if last_word.sub!(rule, replacement) }
+        prefix + last_word
+      end
+    end
+
+    # Split a phrase into two chunks for +apply_inflections+:
+    #  split_phrase('word') # => ['', 'word']
+    #  split_phrase('two words') # => ['two ', 'words']
+    #  split_phrase('two_words') # => ['two_', 'words']
+    #  split_phrase('two-words') # => ['two-', 'words']
+    #  split_phrase('myWord') # => ['my','Word']
+    #  split_phrase('many many words') # => ['many many ','words']
+    def split_phrase(phrase)
+      if last_word = underscore(phrase)[/[a-z0-9]+\Z/i]
+        [phrase[0...-last_word.length], phrase[-last_word.length..-1]]
+      else
+        [phrase, '']
       end
     end
   end

activesupport/test/inflector_test.rb

@@ -17,6 +17,18 @@ def test_pluralize_empty_string
     assert_equal "", ActiveSupport::Inflector.pluralize("")
   end
 
+  def test_pluralize_camel_case_string
+    assert_equal "camelCases", ActiveSupport::Inflector.pluralize("camelCase")
+    assert_equal "OpticalMice", ActiveSupport::Inflector.pluralize("OpticalMouse")
+    assert_equal "SawFish", ActiveSupport::Inflector.pluralize("SawFish")
+  end
+
+  def test_singularize_camel_case_string
+    assert_equal "camelCase", ActiveSupport::Inflector.singularize("camelCases")
+    assert_equal "OpticalMouse", ActiveSupport::Inflector.singularize("OpticalMice")
+    assert_equal "SawFish", ActiveSupport::Inflector.singularize("SawFish")
+  end
+
   ActiveSupport::Inflector.inflections.uncountable.each do |word|
     define_method "test_uncountability_of_#{word}" do
       assert_equal word, ActiveSupport::Inflector.singularize(word)

activesupport/test/inflector_test_cases.rb

@@ -15,6 +15,7 @@ module InflectorTestCases
     "jeans"       => "jeans",
     "funky jeans" => "funky jeans",
     "my money"    => "my money",
+    "your mouse"  => "your mice",
 
     "category"    => "categories",
     "query"       => "queries",
@@ -84,7 +85,6 @@ module InflectorTestCases
     "status"      => "statuses",
     "status_code" => "status_codes",
     "mouse"       => "mice",
-
     "louse"       => "lice",
     "house"       => "houses",
     "octopus"     => "octopi",