fix bug in reference counting None object (#286)

test/runtest.py

@@ -4,6 +4,7 @@ import numpy as np
 import time
 import subprocess32 as subprocess
 import os
+import sys
 
 import test_functions
 import ray.array.remote as ra
@@ -489,5 +490,22 @@ class PythonModeTest(unittest.TestCase):
 
     ray.services.cleanup()
 
+class PythonCExtensionTest(unittest.TestCase):
+
+  def testReferenceCountNone(self):
+    worker_path = os.path.join(os.path.dirname(os.path.abspath(__file__)), "test_worker.py")
+    ray.services.start_ray_local(num_workers=1, worker_path=worker_path)
+
+    # Make sure that we aren't accidentally messing up Python's reference counts.
+    for obj in [None, True, False]:
+      @ray.remote([], [int])
+      def f():
+        return sys.getrefcount(obj)
+      first_count = ray.get(f())
+      second_count = ray.get(f())
+      self.assertEqual(first_count, second_count)
+
+    ray.services.cleanup()
+
 if __name__ == "__main__":
     unittest.main()