Default I18n.enforce_available_locales to true

We will default this option to true from now on to ensure users properly
handle their list of available locales whenever necessary. This option
was added as a security measure and thus Rails will follow it defaulting
to secure option.

Also improve the handling of I18n config options in its railtie, taking
the new enforce_available_locales option into account, by setting it as
the last one in the process. This ensures no other configuration will
trigger a deprecation warning due to that setting.

1 files changed, 10 insertions, 4 deletions

diff --git a/activesupport/lib/active_support/i18n_railtie.rb b/activesupport/lib/active_support/i18n_railtie.rb
index dcdea70443..ac9bca44b6 100644
--- a/activesupport/lib/active_support/i18n_railtie.rb
+++ b/activesupport/lib/active_support/i18n_railtie.rb
@@ -8,6 +8,8 @@ module I18n
     config.i18n.railties_load_path = []
     config.i18n.load_path = []
     config.i18n.fallbacks = ActiveSupport::OrderedOptions.new
+    # Enforce I18n to check the available locales when setting a locale.
+    config.i18n.enforce_available_locales = true
 
     # Set the i18n configuration after initialization since a lot of
     # configuration is still usually done in application initializers.
@@ -31,10 +33,11 @@ module I18n
 
       fallbacks = app.config.i18n.delete(:fallbacks)
 
-      if app.config.i18n.has_key?(:enforce_available_locales)
-        # this option needs to be set before `default_locale=` to work properly.
-        I18n.enforce_available_locales = app.config.i18n.delete(:enforce_available_locales)
-      end
+      # Avoid issues with setting the default_locale by disabling available locales
+      # check while configuring.
+      enforce_available_locales = app.config.i18n.delete(:enforce_available_locales)
+      enforce_available_locales = I18n.enforce_available_locales unless I18n.enforce_available_locales.nil?
+      I18n.enforce_available_locales = false
 
       app.config.i18n.each do |setting, value|
         case setting
@@ -49,6 +52,9 @@ module I18n
 
       init_fallbacks(fallbacks) if fallbacks && validate_fallbacks(fallbacks)
 
+      # Restore avalable locales check so it will take place from now on.
+      I18n.enforce_available_locales = enforce_available_locales
+
       reloader = ActiveSupport::FileUpdateChecker.new(I18n.load_path.dup){ I18n.reload! }
       app.reloaders << reloader
       ActionDispatch::Reloader.to_prepare { reloader.execute_if_updated }