Allow translate default option to accept an array similar to i18n.t. Fixes #29441

actionpack/lib/abstract_controller/translation.rb

@@ -13,7 +13,7 @@ def translate(key, options = {})
         path = controller_path.tr("/", ".")
         defaults = [:"#{path}#{key}"]
         defaults << options[:default] if options[:default]
-        options[:default] = defaults
+        options[:default] = defaults.flatten
         key = "#{path}.#{action_name}#{key}"
       end
       I18n.translate(key, options)

actionpack/test/abstract/translation_test.rb

@@ -62,6 +62,7 @@ def test_lazy_lookup_fallback
       def test_default_translation
         @controller.stub :action_name, :index do
           assert_equal "bar", @controller.t("one.two")
+          assert_equal "baz", @controller.t(".twoz", default: ["baz", :twoz])
         end
       end