Recommend setting enable_reloading on newer Rails versions

Author: nvasilevski

lib/spring/application.rb

@@ -102,9 +102,14 @@ def preload
 
       Rails::Application.initializer :ensure_reloading_is_enabled, group: :all do
         if Rails.application.config.cache_classes
+          config_name, set_to = if Rails.application.config.respond_to?(:enable_reloading=)
+            ["enable_reloading", "true"]
+          else
+            ["cache_classes", "false"]
+          end
           raise <<-MSG.strip_heredoc
             Spring reloads, and therefore needs the application to have reloading enabled.
-            Please, set config.cache_classes to false in config/environments/#{Rails.env}.rb.
+            Please, set config.#{config_name} to #{set_to} in config/environments/#{Rails.env}.rb.
           MSG
         end
       end

test/support/acceptance_test.rb

@@ -144,7 +144,12 @@ def without_gem(name)
         end
         File.write(config_path, config)
 
-        assert_failure "bin/rails runner 1", stderr: "Please, set config.cache_classes to false"
+        expected_error = Regexp.union(
+          "Please, set config.enable_reloading to true",
+          "Please, set config.cache_classes to false"
+        )
+
+        assert_failure "bin/rails runner 1", stderr: expected_error
       end
 
       test "test changes are picked up" do