FEATURE: Localization fallbacks (server-side)

The FallbackLocaleList object tells I18n::Backend::Fallbacks what order the
languages should be attempted in. Because of the translate_accelerator patch,
the SiteSetting.default_locale is *not* guaranteed to be fully loaded after the
server starts, so a call to ensure_loaded! is added after the locale is set for
the current user.

The declarations of config.i18n.fallbacks = true in the environment files were
actually garbage, because the I18n.default_locale was
SiteSetting.default_locale, so there was nothing to fall back to. *derp*

app/controllers/application_controller.rb

@@ -155,6 +155,8 @@ class ApplicationController < ActionController::Base
                   else
                     SiteSetting.default_locale
                   end
+
+    I18n.fallbacks.ensure_loaded!
   end
 
   def store_preloaded(key, json)

config/cloud/cloud66/files/production.rb

@@ -23,11 +23,6 @@ Discourse::Application.configure do
   # Specifies the header that your server uses for sending files
   config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect' # for nginx
 
-  # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
-  # the I18n.default_locale when a translation can not be found)
-  config.i18n.fallbacks = true
-
-
   # you may use other configuration here for mail eg: sendgrid
 
   config.action_mailer.delivery_method = :smtp

config/environments/production.rb

@@ -24,10 +24,6 @@ Discourse::Application.configure do
 
   config.log_level = :info
 
-  # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
-  # the I18n.default_locale when a translation can not be found)
-  config.i18n.fallbacks = true
-
   if GlobalSetting.smtp_address
     settings = {
       address:              GlobalSetting.smtp_address,

config/environments/profile.rb

@@ -27,10 +27,6 @@ Discourse::Application.configure do
   # Specifies the header that your server uses for sending files
   config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect' # for nginx
 
-  # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
-  # the I18n.default_locale when a translation can not be found)
-  config.i18n.fallbacks = true
-
   # we recommend you use mailcatcher https://github.com/sj26/mailcatcher
   config.action_mailer.smtp_settings = { address: "localhost", port: 1025 }
 

config/initializers/i18n.rb

@@ -0,0 +1,24 @@
+# order: after 02-freedom_patches.rb
+
+# Include pluralization module
+require 'i18n/backend/pluralization'
+I18n::Backend::Simple.send(:include, I18n::Backend::Pluralization)
+
+# Include fallbacks module
+require 'i18n/backend/fallbacks'
+I18n.backend.class.send(:include, I18n::Backend::Fallbacks)
+
+# Configure custom fallback order
+class FallbackLocaleList < Hash
+  def [](locale)
+    # user locale, site locale, english
+    # TODO - this can be extended to be per-language for a better user experience
+    # (e.g. fallback zh_TW to zh_CN / vice versa)
+    [locale, SiteSetting.default_locale.to_sym, :en].uniq.compact
+  end
+
+  def ensure_loaded!
+    self[I18n.locale].each { |l| I18n.ensure_loaded! l }
+  end
+end
+I18n.fallbacks = FallbackLocaleList.new

config/initializers/pluralization.rb

@@ -1,2 +0,0 @@
-require "i18n/backend/pluralization"
-I18n::Backend::Simple.send(:include, I18n::Backend::Pluralization)

lib/freedom_patches/translate_accelerator.rb

@@ -59,6 +59,11 @@ module I18n
       end
     end
 
+    def ensure_loaded!(locale)
+      @loaded_locales ||= []
+      load_locale locale unless @loaded_locales.include?(locale)
+    end
+
     def translate(key, *args)
       load_locale(config.locale) unless @loaded_locales.include?(config.locale)
       return translate_no_cache(key, *args) if args.length > 0