Fall through to I18n.fallbacks when defined

.travis.yml

@@ -25,6 +25,7 @@ env:
   - DB=mysql ORM=sequel SEQUEL_VERSION=5
   - DB=sqlite3 ORM=sequel SEQUEL_VERSION=5
   - DB=sqlite3 ORM= TEST_PERFORMANCE=true
+  - DB=sqlite3 ORM= I18N_FALLBACKS=true
 matrix:
   fast_finish: true
   allow_failures:

lib/mobility.rb

@@ -30,6 +30,7 @@ module Mobility
   require "mobility/backends"
   require "mobility/backend_resetter"
   require "mobility/configuration"
+  require "mobility/fallbacks"
   require "mobility/loaded"
   require "mobility/plugins"
   require "mobility/translates"

lib/mobility/configuration.rb

@@ -103,7 +103,7 @@ def default_accessor_locales
     def initialize
       @accessor_method = :translates
       @query_method = :i18n
-      @fallbacks_generator = lambda { |fallbacks| I18n::Locale::Fallbacks.new(fallbacks) }
+      @fallbacks_generator = lambda { |fallbacks| Mobility::Fallbacks.build(fallbacks) }
       @default_accessor_locales = lambda { I18n.available_locales }
       @default_options = Options[{
         cache: true,

lib/mobility/fallbacks.rb

@@ -0,0 +1,28 @@
+module Mobility
+=begin
+
+Subclasses +I18n::Locale::Fallbacks+ such that instances of this class
+fall through to fallbacks defined in +I18n.fallbacks+. This allows models to
+customize fallbacks while still falling through to any fallbacks defined
+globally.
+
+=end
+  class Fallbacks < ::I18n::Locale::Fallbacks
+    # @param [Symbol] locale
+    # @return [Array] locales
+    def [](locale)
+      super | I18n.fallbacks[locale]
+    end
+
+    # For this set of fallbacks, return a new fallbacks hash.
+    # @param [Hash] fallbacks
+    # @return [I18n::Locale::Fallbacks,Mobility::Fallbacks] fallbacks hash
+    def self.build(fallbacks)
+      if I18n.respond_to?(:fallbacks)
+        new(fallbacks)
+      else
+        I18n::Locale::Fallbacks.new(fallbacks)
+      end
+    end
+  end
+end

spec/spec_helper.rb

@@ -19,6 +19,8 @@
 require 'mobility'
 require "mobility/backends/null"
 
+require "i18n/backend/fallbacks" if ENV['I18N_FALLBACKS']
+
 I18n.enforce_available_locales = true
 I18n.available_locales = [:en, :'en-US', :ja, :fr, :de, :'de-DE', :cz, :pl, :pt, :'pt-BR']