Merge pull request rails#54143 from Shopify/fix-action-controller-live-thread-locals-in-test

Stop clearing thread locals in test environment when controller includes ActionController::Live

Author: tenderlove

actionpack/lib/action_controller/metal/live.rb

@@ -301,9 +301,8 @@ def process(name)
               error = e
             end
           ensure
-            # Ensure we clean up any thread locals we copied so that the thread can reused.
             ActiveSupport::IsolatedExecutionState.clear
-            locals.each { |k, _| t2[k] = nil }
+            clean_up_thread_locals(locals, t2)
 
             @_response.commit!
           end
@@ -377,6 +376,11 @@ def new_controller_thread # :nodoc:
         end
       end
 
+      # Ensure we clean up any thread locals we copied so that the thread can reused.
+      def clean_up_thread_locals(locals, thread) # :nodoc:
+        locals.each { |k, _| thread[k] = nil }
+      end
+
       def self.live_thread_pool_executor
         @live_thread_pool_executor ||= Concurrent::CachedThreadPool.new(name: "action_controller.live")
       end

actionpack/lib/action_controller/test_case.rb

@@ -29,6 +29,14 @@ def new_controller_thread # :nodoc:
       yield
     end
 
+    # Because of the above, we need to prevent the clearing of thread locals, since
+    # no new thread is actually spawned in the test environment.
+    alias_method :original_clean_up_thread_locals, :clean_up_thread_locals
+
+    silence_redefinition_of_method :clean_up_thread_locals
+    def clean_up_thread_locals(*args) # :nodoc:
+    end
+
     # Avoid a deadlock from the queue filling up
     Buffer.queue_size = nil
   end

actionpack/test/controller/live_stream_test.rb

@@ -360,6 +360,10 @@ def setup
       def @controller.new_controller_thread(&block)
         original_new_controller_thread(&block)
       end
+
+      def @controller.clean_up_thread_locals(*args)
+        original_clean_up_thread_locals(*args)
+      end
     end
 
     def test_set_cookie
@@ -658,6 +662,30 @@ def test_response_buffer_do_not_respond_to_to_ary
     end
   end
 
+  class LiveControllerThreadTest < ActionController::TestCase
+    class TestController < ActionController::Base
+      include ActionController::Live
+
+      def greet
+        response.headers["Content-Type"] = "text/event-stream"
+        %w{ hello world }.each do |word|
+          response.stream.write word
+        end
+        response.stream.close
+      end
+    end
+
+    tests TestController
+
+    def test_thread_locals_do_not_get_reset_in_test_environment
+      Thread.current[:setting] = "aaron"
+
+      get :greet
+
+      assert_equal "aaron", Thread.current[:setting]
+    end
+  end
+
   class BufferTest < ActionController::TestCase
     def test_nil_callback
       buf = ActionController::Live::Buffer.new nil