render_to_string Regression Outside of Real Requests in Rails 5.0.0.rc1 (#25308)

* Restore the functionality of PR#14129, but do so with not nil to better indicate the purpose of the conditional

* Add a test when render_to_string called on ActionController::Base.new()

2 files changed, 8 insertions, 1 deletions

diff --git a/actionpack/lib/abstract_controller/rendering.rb b/actionpack/lib/abstract_controller/rendering.rb
index a6fb0dbe1d..4ba2c26949 100644
--- a/actionpack/lib/abstract_controller/rendering.rb
+++ b/actionpack/lib/abstract_controller/rendering.rb
@@ -122,7 +122,7 @@ module AbstractController
     def _normalize_render(*args, &block)
       options = _normalize_args(*args, &block)
       #TODO: remove defined? when we restore AP <=> AV dependency
-      if defined?(request) && request.variant.present?
+      if defined?(request) && !request.nil? && request.variant.present?
         options[:variant] = request.variant
       end
       _normalize_options(options)
diff --git a/actionpack/test/controller/render_test.rb b/actionpack/test/controller/render_test.rb
index f42efd35af..8d3134630d 100644
--- a/actionpack/test/controller/render_test.rb
+++ b/actionpack/test/controller/render_test.rb
@@ -564,6 +564,13 @@ class MetalRenderTest < ActionController::TestCase
   end
 end
 
+class ActionControllerBaseRenderTest < ActionController::TestCase
+  def test_direct_render_to_string
+    ac = ActionController::Base.new()
+    assert_equal "Hello world!", ac.render_to_string(template: 'test/hello_world')
+  end
+end
+
 class ImplicitRenderTest < ActionController::TestCase
   tests ImplicitRenderTestController