Clean up locale fallback code

It was breaking on locales with more than two segments (e.g., `zh-Hant-HK`)

Beyond that, I pulled out the fallback code and exposed it so that downstream consumers can use it too.
I structured it in a similar manner as `ruby-i18n`'s [`I18n::Locale::Fallbacks`](https://github.com/ruby-i18n/i18n/blob/535459ad1201e7cc97a071bd5d9f0e1d5406069e/lib/i18n/locale/fallbacks.rb).

I also changed the keys and values in `ParentLocales` to be symbols, which simplifies the code.

It's still not fully correct for locales that contain scripts (e.g., `ff-Adlm-GH`).
That will be a different commit.

CHANGELOG.md

@@ -28,6 +28,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Sort the exported data by key, [#82](https://github.com/ruby-i18n/ruby-cldr/pull/82)
 - Prune empty hashes / files before outputting, [#86](https://github.com/ruby-i18n/ruby-cldr/pull/86)
 - Re-add the `ParentLocales` component, this time as a shared component, [#91](https://github.com/ruby-i18n/ruby-cldr/pull/91)
+- Changed the keys and values of `ParentLocales` component to be symbols, [#101](https://github.com/ruby-i18n/ruby-cldr/pull/101)
+- Fixed bug with fallbacks for locales that had more than two segments, [#101](https://github.com/ruby-i18n/ruby-cldr/pull/101)
 
 ---
 

lib/cldr.rb

@@ -3,5 +3,12 @@
 module Cldr
   autoload :Data,   'cldr/data'
   autoload :Export, 'cldr/export'
+  autoload :Locale, 'cldr/locale'
   autoload :Format, 'cldr/format'
-end
+
+  class << self
+    def fallbacks
+      @@fallbacks ||= Cldr::Locale::Fallbacks.new
+    end
+  end
+end

lib/cldr/export.rb

@@ -135,25 +135,12 @@ def locales(locale, component, options)
         locale = to_i18n(locale)
 
         locales = if options[:merge]
-          defined_parents = Cldr::Export::Data::ParentLocales.new
-
-          ancestry = [locale.to_s]
-          loop do
-            if defined_parents[ancestry.last]
-              ancestry << defined_parents[ancestry.last]
-            elsif I18n::Locale::Tag.tag(ancestry.last).self_and_parents.count > 1
-              ancestry << I18n::Locale::Tag.tag(ancestry.last).self_and_parents.last
-            else
-              break
-            end
-          end
-
-          ancestry.map(&:to_sym)
+          Cldr.fallbacks[locale]
         else
-          [locale]
+          [locale, :root]
         end
 
-        locales << :root if should_merge_root?(locale, component, options)
+        locales.pop unless should_merge_root?(locale, component, options)
         locales
       end
 

lib/cldr/export/data/parent_locales.rb

@@ -9,8 +9,8 @@ def initialize(_ = nil)
           doc = File.open(path) { |file| Nokogiri::XML(file) }
 
           doc.xpath('//parentLocales/parentLocale').each do |node|
-            parent = Cldr::Export.to_i18n(node.attr('parent')).to_s
-            locales = node.attr('locales').split(' ').map {|locale| Cldr::Export.to_i18n(locale) }.map(&:to_s)
+            parent = Cldr::Export.to_i18n(node.attr('parent'))
+            locales = node.attr('locales').split(' ').map {|locale| Cldr::Export.to_i18n(locale) }
 
             locales.each do |locale|
               self[locale] = parent

lib/cldr/locale/fallbacks.rb

@@ -0,0 +1,22 @@
+module Cldr
+  module Locale
+    class Fallbacks < Hash
+      def [](locale)
+        defined_parents = Cldr::Export::Data::ParentLocales.new
+
+        ancestry = [locale]
+        loop do
+          if defined_parents[ancestry.last]
+            ancestry << defined_parents[ancestry.last]
+          elsif I18n::Locale::Tag.tag(ancestry.last).parents.count > 0
+            ancestry << I18n::Locale::Tag.tag(ancestry.last).parents.first.to_sym
+          else
+            break
+          end
+        end
+        ancestry << :root unless ancestry.last == :root
+        store(locale, ancestry)
+      end
+    end
+  end
+end

test/locale/fallbacks_test.rb

@@ -0,0 +1,18 @@
+# encoding: utf-8
+
+require File.expand_path(File.join(File.dirname(__FILE__) + '/../test_helper'))
+
+class TestFallbacks < Test::Unit::TestCase
+  test "fallbacks does basic hyphen chopping" do
+    assert_equal [:root], Cldr.fallbacks[:root]
+    assert_equal [:en, :root], Cldr.fallbacks[:en]
+    assert_equal [:"fr-CA", :fr, :root], Cldr.fallbacks[:"fr-CA"]
+    assert_equal [:"zh-Hant-HK", :"zh-Hant", :root], Cldr.fallbacks[:"zh-Hant-HK"]
+  end
+
+  test "fallbacks observe explicit parent overrides" do
+    assert_equal [:"az-Arab", :root], Cldr.fallbacks[:"az-Arab"]
+    assert_equal [:"en-CH", :"en-150", :"en-001", :en, :root], Cldr.fallbacks[:"en-CH"]
+    assert_equal [:"zh-Hant", :root], Cldr.fallbacks[:"zh-Hant"]
+  end
+end