Make ActiveSupport::Inflector locale aware and multilingual

The Inflector is currently not very supportive of internationalized
websites. If a user wants to singularize and/or pluralize words based on
any locale other than English, they must define each case in locale
files. Rather than create large locale files with mappings between
singular and plural words, why not allow the Inflector to accept a
locale?

This patch makes ActiveSupport::Inflector locale aware and uses `:en`` unless
otherwise specified. Users will still be provided a list of English (:en)
inflections, but they may additionally define inflection rules for other
locales. Each list is kept separately and permanently. There is no reason to
limit users to one list of inflections:

    ActiveSupport::Inflector.inflections(:es) do |inflect|
      inflect.plural(/$/, 's')
      inflect.plural(/([^aeéiou])$/i, '\1es')
      inflect.plural(/([aeiou]s)$/i, '\1')
      inflect.plural(/z$/i, 'ces')
      inflect.plural(/á([sn])$/i, 'a\1es')
      inflect.plural(/é([sn])$/i, 'e\1es')
      inflect.plural(/í([sn])$/i, 'i\1es')
      inflect.plural(/ó([sn])$/i, 'o\1es')
      inflect.plural(/ú([sn])$/i, 'u\1es')

      inflect.singular(/s$/, '')
      inflect.singular(/es$/, '')

      inflect.irregular('el', 'los')
    end

    'ley'.pluralize(:es)   # => "leyes"
    'ley'.pluralize(:en)   # => "leys"
    'avión'.pluralize(:es) # => "aviones"
    'avión'.pluralize(:en) # => "avións"

A multilingual Inflector should be of use to anybody that is tasked with
internationalizing their Rails application.

Signed-off-by: David Celis <david@davidcelis.com>

2 files changed, 30 insertions, 15 deletions

diff --git a/activesupport/lib/active_support/inflector/inflections.rb b/activesupport/lib/active_support/inflector/inflections.rb
index c9e50a9462..091692e5a4 100644
--- a/activesupport/lib/active_support/inflector/inflections.rb
+++ b/activesupport/lib/active_support/inflector/inflections.rb
@@ -1,13 +1,15 @@
 require 'active_support/core_ext/array/prepend_and_append'
+require 'active_support/i18n'
 
 module ActiveSupport
   module Inflector
     extend self
 
     # A singleton instance of this class is yielded by Inflector.inflections, which can then be used to specify additional
-    # inflection rules.
+    # inflection rules. If passed an optional locale, rules for other languages can be specified. The default locale is
+    # <tt>:en</tt>. Only rules for English are provided.
     #
-    #   ActiveSupport::Inflector.inflections do |inflect|
+    #   ActiveSupport::Inflector.inflections(:en) do |inflect|
     #     inflect.plural /^(ox)$/i, '\1\2en'
     #     inflect.singular /^(ox)en/i, '\1'
     #
@@ -20,8 +22,9 @@ module ActiveSupport
     # pluralization and singularization rules that is runs. This guarantees that your rules run before any of the rules that may
     # already have been loaded.
     class Inflections
-      def self.instance
-        @__instance__ ||= new
+      def self.instance(locale = :en)
+        @__instance__ ||= Hash.new { |h, k| h[k] = new }
+        @__instance__[locale]
       end
 
       attr_reader :plurals, :singulars, :uncountables, :humans, :acronyms, :acronym_regex
@@ -160,16 +163,18 @@ module ActiveSupport
     end
 
     # Yields a singleton instance of Inflector::Inflections so you can specify additional
-    # inflector rules.
+    # inflector rules. If passed an optional locale, rules for other languages can be specified.
+    # If not specified, defaults to <tt>:en</tt>. Only rules for English are provided.
+    # 
     #
-    #   ActiveSupport::Inflector.inflections do |inflect|
+    #   ActiveSupport::Inflector.inflections(:en) do |inflect|
     #     inflect.uncountable "rails"
     #   end
-    def inflections
+    def inflections(locale = :en)
       if block_given?
-        yield Inflections.instance
+        yield Inflections.instance(locale)
       else
-        Inflections.instance
+        Inflections.instance(locale)
       end
     end
   end
diff --git a/activesupport/lib/active_support/inflector/methods.rb b/activesupport/lib/active_support/inflector/methods.rb
index c14a43de0d..44214d16fa 100644
--- a/activesupport/lib/active_support/inflector/methods.rb
+++ b/activesupport/lib/active_support/inflector/methods.rb
@@ -10,31 +10,41 @@ module ActiveSupport
   #
   # The Rails core team has stated patches for the inflections library will not be accepted
   # in order to avoid breaking legacy applications which may be relying on errant inflections.
-  # If you discover an incorrect inflection and require it for your application, you'll need
-  # to correct it yourself (explained below).
+  # If you discover an incorrect inflection and require it for your application or wish to
+  # define rules for languages other than English, please correct or add them yourself (explained below).
   module Inflector
     extend self
 
     # Returns the plural form of the word in the string.
     #
+    # If passed an optional +locale+ parameter, the word will be
+    # pluralized using rules defined for that language. By default,
+    # this parameter is set to <tt>:en</tt>.
+    #
     #   "post".pluralize             # => "posts"
     #   "octopus".pluralize          # => "octopi"
     #   "sheep".pluralize            # => "sheep"
     #   "words".pluralize            # => "words"
     #   "CamelOctopus".pluralize     # => "CamelOctopi"
-    def pluralize(word)
-      apply_inflections(word, inflections.plurals)
+    #   "ley".pluralize(:es)         # => "leyes"
+    def pluralize(word, locale = :en)
+      apply_inflections(word, inflections(locale).plurals)
     end
 
     # The reverse of +pluralize+, returns the singular form of a word in a string.
     #
+    # If passed an optional +locale+ parameter, the word will be
+    # pluralized using rules defined for that language. By default,
+    # this parameter is set to <tt>:en</tt>.
+    #
     #   "posts".singularize            # => "post"
     #   "octopi".singularize           # => "octopus"
     #   "sheep".singularize            # => "sheep"
     #   "word".singularize             # => "word"
     #   "CamelOctopi".singularize      # => "CamelOctopus"
-    def singularize(word)
-      apply_inflections(word, inflections.singulars)
+    #   "leyes".singularize(:es)       # => "ley"
+    def singularize(word, locale = :en)
+      apply_inflections(word, inflections(locale).singulars)
     end
 
     # By default, +camelize+ converts strings to UpperCamelCase. If the argument to +camelize+