Issue a more user-friendly error message if a variable's initializer is from inside a control-flow scope, such as tf.cond() or tf.while_loop().

Fixes #8604.

PiperOrigin-RevId: 157516279

tensorflow/python/kernel_tests/resource_variable_ops_test.py

@@ -25,6 +25,7 @@ from tensorflow.python.framework import errors
 from tensorflow.python.framework import ops
 from tensorflow.python.framework import test_util
 from tensorflow.python.ops import array_ops
+from tensorflow.python.ops import control_flow_ops
 from tensorflow.python.ops import init_ops
 from tensorflow.python.ops import math_ops
 from tensorflow.python.ops import resource_variable_ops
@@ -256,6 +257,19 @@ class ResourceVariableOpsTest(test_util.TensorFlowTestCase):
       v.initializer.run(feed_dict={v.initial_value: 3.0})
       self.assertEqual(3.0, v.value().eval())
 
+  def testControlFlowInitialization(self):
+    """Expects an error if an initializer is in a control-flow scope."""
+    def cond(i, _):
+      return i < 10
+
+    def body(i, _):
+      zero = array_ops.zeros([], dtype=dtypes.int32)
+      v = resource_variable_ops.ResourceVariable(initial_value=zero)
+      return (i + 1, v.read_value())
+
+    with self.assertRaisesRegexp(ValueError, "inside a control-flow"):
+      control_flow_ops.while_loop(cond, body, [0, 0])
+
 
 if __name__ == "__main__":
   test.main()

tensorflow/python/kernel_tests/variables_test.py

@@ -231,6 +231,19 @@ class VariablesTestCase(test.TestCase):
       sess.run(v0.initializer)
       sess.run(add)
 
+  def testControlFlowInitialization(self):
+    """Expects an error if an initializer is in a control-flow scope."""
+    def cond(i, _):
+      return i < 10
+
+    def body(i, _):
+      zero = array_ops.zeros([], dtype=dtypes.int32)
+      v = variables.Variable(initial_value=zero)
+      return (i + 1, v.read_value())
+
+    with self.assertRaisesRegexp(ValueError, "inside a control-flow"):
+      control_flow_ops.while_loop(cond, body, [0, 0])
+
   def testUseVariableAsTensor(self):
     with self.test_session():
       var_x = variables.Variable(2.0)

tensorflow/python/ops/resource_variable_ops.py

@@ -183,6 +183,14 @@ class ResourceVariable(variables.Variable):
         else:
           self._initial_value = ops.convert_to_tensor(
               initial_value, name="initial_value", dtype=dtype)
+          # pylint: disable=protected-access
+          if self._initial_value.op._get_control_flow_context() is not None:
+            raise ValueError(
+                "Initializer for variable %s is from inside a control-flow "
+                "construct, such as a loop or conditional. When creating a "
+                "variable inside a loop or conditional, use a lambda as the "
+                "initializer." % name)
+          # pylint: enable=protected-access
           self._handle = gen_resource_variable_ops.var_handle_op(
               shape=self._initial_value.get_shape(),
               dtype=self._initial_value.dtype.base_dtype,

tensorflow/python/ops/variables.py

@@ -282,11 +282,20 @@ class Variable(object):
                 shape,
                 self._initial_value.dtype.base_dtype,
                 name=name)
+          # pylint: enable=protected-access
 
         # Or get the initial value from a Tensor or Python object.
         else:
           self._initial_value = ops.convert_to_tensor(
               initial_value, name="initial_value", dtype=dtype)
+          # pylint: disable=protected-access
+          if self._initial_value.op._get_control_flow_context() is not None:
+            raise ValueError(
+                "Initializer for variable %s is from inside a control-flow "
+                "construct, such as a loop or conditional. When creating a "
+                "variable inside a loop or conditional, use a lambda as the "
+                "initializer." % name)
+          # pylint: enable=protected-access
           shape = (self._initial_value.get_shape()
                    if validate_shape else tensor_shape.unknown_shape())
           # In this case, the variable op can't be created until after the