1 files changed, 125 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/i18n_railtie.rb b/activesupport/lib/active_support/i18n_railtie.rb
new file mode 100644
index 0000000000..584930e413
--- /dev/null
+++ b/activesupport/lib/active_support/i18n_railtie.rb
@@ -0,0 +1,125 @@
+# frozen_string_literal: true
+
+require "active_support"
+require "active_support/core_ext/array/wrap"
+
+# :enddoc:
+
+module I18n
+  class Railtie < Rails::Railtie
+    config.i18n = ActiveSupport::OrderedOptions.new
+    config.i18n.railties_load_path = []
+    config.i18n.load_path = []
+    config.i18n.fallbacks = ActiveSupport::OrderedOptions.new
+
+    # Set the i18n configuration after initialization since a lot of
+    # configuration is still usually done in application initializers.
+    config.after_initialize do |app|
+      I18n::Railtie.initialize_i18n(app)
+    end
+
+    # Trigger i18n config before any eager loading has happened
+    # so it's ready if any classes require it when eager loaded.
+    config.before_eager_load do |app|
+      I18n::Railtie.initialize_i18n(app)
+    end
+
+    @i18n_inited = false
+
+    # Setup i18n configuration.
+    def self.initialize_i18n(app)
+      return if @i18n_inited
+
+      fallbacks = app.config.i18n.delete(:fallbacks)
+
+      # 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 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
+          reloadable_paths = value
+          app.config.i18n.load_path.unshift(*value.flat_map(&:existent))
+        when :load_path
+          I18n.load_path += value
+        else
+          I18n.send("#{setting}=", value)
+        end
+      end
+
+      init_fallbacks(fallbacks) if fallbacks && validate_fallbacks(fallbacks)
+
+      # Restore available locales check so it will take place from now on.
+      I18n.enforce_available_locales = enforce_available_locales
+
+      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
+      app.reloader.to_run do
+        reloader.execute_if_updated { require_unload_lock! }
+      end
+      reloader.execute
+
+      @i18n_inited = true
+    end
+
+    def self.include_fallbacks_module
+      I18n.backend.class.include(I18n::Backend::Fallbacks)
+    end
+
+    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
+          [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)
+    end
+
+    def self.validate_fallbacks(fallbacks)
+      case fallbacks
+      when ActiveSupport::OrderedOptions
+        !fallbacks.empty?
+      when TrueClass, Array, Hash
+        true
+      else
+        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