1 files changed, 43 insertions, 18 deletions

diff --git a/activesupport/lib/active_support/i18n_railtie.rb b/activesupport/lib/active_support/i18n_railtie.rb
index 95f3f6255a..584930e413 100644
--- a/activesupport/lib/active_support/i18n_railtie.rb
+++ b/activesupport/lib/active_support/i18n_railtie.rb
@@ -1,7 +1,10 @@
+# frozen_string_literal: true
+
 require "active_support"
-require "active_support/file_update_checker"
 require "active_support/core_ext/array/wrap"
 
+# :enddoc:
+
 module I18n
   class Railtie < Rails::Railtie
     config.i18n = ActiveSupport::OrderedOptions.new
@@ -21,8 +24,6 @@ module I18n
       I18n::Railtie.initialize_i18n(app)
     end
 
-  protected
-
     @i18n_inited = false
 
     # Setup i18n configuration.
@@ -37,10 +38,12 @@ module I18n
       enforce_available_locales = I18n.enforce_available_locales if enforce_available_locales.nil?
       I18n.enforce_available_locales = false
 
+      reloadable_paths = []
       app.config.i18n.each do |setting, value|
         case setting
         when :railties_load_path
-          app.config.i18n.load_path.unshift(*value)
+          reloadable_paths = value
+          app.config.i18n.load_path.unshift(*value.flat_map(&:existent))
         when :load_path
           I18n.load_path += value
         else
@@ -53,14 +56,17 @@ module I18n
       # Restore available 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! }
+      directories = watched_dirs_with_extensions(reloadable_paths)
+      reloader = app.config.file_watcher.new(I18n.load_path.dup, directories) do
+        I18n.load_path.keep_if { |p| File.exist?(p) }
+        I18n.load_path |= reloadable_paths.flat_map(&:existent)
+
+        I18n.reload!
+      end
+
       app.reloaders << reloader
-      ActionDispatch::Reloader.to_prepare do
-        reloader.execute_if_updated
-        # TODO: remove the following line as soon as the return value of
-        # callbacks is ignored, that is, returning `false` does not
-        # display a deprecation warning or halts the callback chain.
-        true
+      app.reloader.to_run do
+        reloader.execute_if_updated { require_unload_lock! }
       end
       reloader.execute
 
@@ -74,13 +80,26 @@ module I18n
     def self.init_fallbacks(fallbacks)
       include_fallbacks_module
 
-      args = case fallbacks
-      when ActiveSupport::OrderedOptions
-        [*(fallbacks[:defaults] || []) << fallbacks[:map]].compact
-      when Hash, Array
-        Array.wrap(fallbacks)
-      else # TrueClass
-        []
+      args = \
+        case fallbacks
+        when ActiveSupport::OrderedOptions
+          [*(fallbacks[:defaults] || []) << fallbacks[:map]].compact
+        when Hash, Array
+          Array.wrap(fallbacks)
+        else # TrueClass
+          [I18n.default_locale]
+        end
+
+      if args.empty? || args.first.is_a?(Hash)
+        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          Using I18n fallbacks with an empty `defaults` sets the defaults to
+          include the `default_locale`. This behavior will change in Rails 6.1.
+          If you desire the default locale to be included in the defaults, please
+          explicitly configure it with `config.i18n.fallbacks.defaults =
+          [I18n.default_locale]` or `config.i18n.fallbacks = [I18n.default_locale,
+          {...}]`
+        MSG
+        args.unshift I18n.default_locale
       end
 
       I18n.fallbacks = I18n::Locale::Fallbacks.new(*args)
@@ -96,5 +115,11 @@ module I18n
         raise "Unexpected fallback type #{fallbacks.inspect}"
       end
     end
+
+    def self.watched_dirs_with_extensions(paths)
+      paths.each_with_object({}) do |path, result|
+        result[path.absolute_current] = path.extensions
+      end
+    end
   end
 end