Cleaner error messages for RNNCell scope failures.

Change: 148832474

2 files changed, 26 insertions, 3 deletions

diff --git a/tensorflow/contrib/rnn/python/kernel_tests/core_rnn_cell_test.py b/tensorflow/contrib/rnn/python/kernel_tests/core_rnn_cell_test.py
index 8b0a9a2bbf..b38f08d4d5 100644
--- a/tensorflow/contrib/rnn/python/kernel_tests/core_rnn_cell_test.py
+++ b/tensorflow/contrib/rnn/python/kernel_tests/core_rnn_cell_test.py
@@ -344,6 +344,29 @@ class RNNCellTest(test.TestCase):
       outputs, _ = cell(x, m)
       self.assertTrue("cpu:14159" in outputs.device.lower())
 
+  def testUsingSecondCellInScopeWithExistingVariablesFails(self):
+    # This test should go away when this behavior is no longer an
+    # error (Approx. May 2017)
+    cell1 = core_rnn_cell_impl.LSTMCell(3)
+    cell2 = core_rnn_cell_impl.LSTMCell(3)
+    x = array_ops.zeros([1, 3])
+    m = core_rnn_cell_impl.LSTMStateTuple(*[array_ops.zeros([1, 3])] * 2)
+    cell1(x, m)
+    with self.assertRaisesRegexp(ValueError, r"LSTMCell\(..., reuse=True\)"):
+      cell2(x, m)
+
+  def testUsingCellInDifferentScopeFromFirstCallFails(self):
+    # This test should go away when this behavior is no longer an
+    # error (Approx. May 2017)
+    cell = core_rnn_cell_impl.LSTMCell(3)
+    x = array_ops.zeros([1, 3])
+    m = core_rnn_cell_impl.LSTMStateTuple(*[array_ops.zeros([1, 3])] * 2)
+    with variable_scope.variable_scope("scope1"):
+      cell(x, m)
+    with variable_scope.variable_scope("scope2"):
+      with self.assertRaisesRegexp(ValueError, r"Attempt to reuse RNNCell"):
+        cell(x, m)
+
   def testDropoutWrapper(self):
     with self.test_session() as sess:
       with variable_scope.variable_scope(
diff --git a/tensorflow/contrib/rnn/python/ops/core_rnn_cell_impl.py b/tensorflow/contrib/rnn/python/ops/core_rnn_cell_impl.py
index 75c8cdc6ae..148d2ef93a 100644
--- a/tensorflow/contrib/rnn/python/ops/core_rnn_cell_impl.py
+++ b/tensorflow/contrib/rnn/python/ops/core_rnn_cell_impl.py
@@ -81,11 +81,11 @@ def _checked_scope(cell, scope, reuse=None, **kwargs):
       if weights_found and reuse is None:
         raise ValueError(
             "Attempt to have a second RNNCell use the weights of a variable "
-            "scope that already has weights: '%s' (and RNNCell was not "
-            "constructed with reuse=True).  "
+            "scope that already has weights: '%s'; and the cell was not "
+            "constructed as %s(..., reuse=True).  "
             "To share the weights of an RNNCell, simply "
             "reuse it in your second calculation, or create a new one with "
-            "the argument reuse=True." % scope_name)
+            "the argument reuse=True." % (scope_name, type(cell).__name__))
 
     # Everything is OK.  Update the cell's scope and yield it.
     cell._scope = checking_scope  # pylint: disable=protected-access