Ensure that functions created with tfe.defun create ResourceVariables, not

RefVariables.

Creating and using RefVariables inside functions was never fully supported
and fails in obscure ways.

PiperOrigin-RevId: 208666153

tensorflow/python/eager/function.py

@@ -42,6 +42,7 @@ from tensorflow.python.ops import control_flow_ops
 from tensorflow.python.ops import functional_ops
 from tensorflow.python.ops import gradients_impl
 from tensorflow.python.ops import resource_variable_ops
+from tensorflow.python.ops import variable_scope
 from tensorflow.python.training import distribute
 from tensorflow.python.util import compat
 from tensorflow.python.util import nest
@@ -832,6 +833,8 @@ def _trace_and_define_function(name, python_func, compiled, args, kwds,
   func_graph = FuncGraph(_inference_name(name), graph=ops.get_default_graph())
 
   with func_graph.as_default(), AutomaticControlDependencies() as a:
+    variable_scope.get_variable_scope().set_use_resource(True)
+
     if signature is None:
       func_args = _get_defun_inputs_from_args(args)
       func_kwds = _get_defun_inputs_from_args(kwds)

tensorflow/python/eager/function_test.py

@@ -397,6 +397,18 @@ class FunctionTest(test.TestCase):
       compiled = function.defun(f)
       compiled()
 
+  @test_util.run_in_graph_and_eager_modes
+  def testDefunForcesResourceVariables(self):
+
+    def variable_creator():
+      return variables.Variable(0.0).read_value()
+
+    defined = function.defun(variable_creator)
+    defined()  # Create the variable.
+    self.assertEqual(len(defined.variables), 1)
+    self.assertIsInstance(
+        defined.variables[0], resource_variable_ops.ResourceVariable)
+
   def testDefunDifferentiable(self):
     v = resource_variable_ops.ResourceVariable(1.0)