[tfdbg2] Fix num_outputs properties when execution or graph op has no output

The previous assumption that `self._output_tensor_ids` is always a tuple
is incorrect. It can be `None` for ops without output tensors.

Also in this CL: Clarify when properties are `None` and when they are
`tuple`s in doc strings of the data objects.

PiperOrigin-RevId: 315261796
Change-Id: I398192ba4451e9d8087a2b9e934dff3f561b651a

tensorflow/python/debug/lib/debug_events_reader.py

@@ -308,14 +308,17 @@ class Execution(ExecutionDigest):
     graph_id: ID of the executed FuncGraph (applicable only the execution of a
       tf.function). `None` for the eager execution of an individual op.
     input_tensor_ids: IDs of the input (eager) tensor(s) for this execution, if
-      any.
+      any. If the eager execution has no input tensor, this is `None`. Else,
+      this is a `tuple` of `int`s.
     output_tensor_ids: IDs of the output (eager) tensor(s) from this execution,
-      if any.
+      if any. If the eager execution produces no output tensor, this is `None`.
+      Else, this is a `tuple` of `int`s.
     debug_tensor_values: Values of the debug tensor(s), applicable only to
       non-FULL_TENSOR tensor debug mode. A tuple of list of numbers. Each
       element of the tuple corresponds to an output tensor of the execution.
       See documentation of the various TensorDebugModes for the semantics of the
-      numbers.
+      numbers. If the eager execution produces no output tensor, this is
+      `None`. Else, this is a `tuple` of `list`s.
   """
 
   def __init__(self,
@@ -362,7 +365,7 @@ class Execution(ExecutionDigest):
 
   @property
   def num_outputs(self):
-    return len(self._output_tensor_ids)
+    return len(self._output_tensor_ids) if self._output_tensor_ids else 0
 
   @property
   def output_tensor_ids(self):
@@ -542,6 +545,8 @@ class GraphOpCreationDigest(BaseDigest):
     op_type: Type name of the op (e.g., "MatMul").
     op_name: Name of the op (e.g., "dense_1/MatMul").
     output_tensor_ids: Debugger-generated IDs for the output(s) of the op.
+      If the op produces no output tensor, this is `None`. Else, this is a
+      `tuple` of `int`s.
     input_names: Names of the input tensors to the op.
     device_name: The name of the device that the op is placed on (if available).
     host_name: Name of the host on which the op is created.
@@ -588,7 +593,7 @@ class GraphOpCreationDigest(BaseDigest):
 
   @property
   def num_outputs(self):
-    return len(self._output_tensor_ids)
+    return len(self._output_tensor_ids) if self.output_tensor_ids else 0
 
   @property
   def input_names(self):

tensorflow/python/debug/lib/debug_events_writer_test.py

@@ -583,7 +583,7 @@ class DebugEventsWriterTest(dumping_callback_test_lib.DumpingCallbackTestBase,
     self.assertEqual(traces[-1].op_name, "Op_%d" % (expected_end - 1))
 
 
-class DataObjectsTest(test_util.TensorFlowTestCase):
+class DataObjectsTest(test_util.TensorFlowTestCase, parameterized.TestCase):
 
   def jsonRoundTripCheck(self, obj):
     self.assertEqual(
@@ -660,6 +660,22 @@ class DataObjectsTest(test_util.TensorFlowTestCase):
     self.assertIsNone(json["output_tensor_ids"])
     self.assertIsNone(json["debug_tensor_values"])
 
+  @parameterized.named_parameters(
+      ("EmptyList", []),
+      ("None", None),
+  )
+  def testExecutionWithNoOutputTensorsReturnsZeroForNumOutputs(
+      self, output_tensor_ids):
+    execution = debug_events_reader.Execution(
+        debug_events_reader.ExecutionDigest(1234, 5678, "FooOp"),
+        "localhost", ("a1", "b2"),
+        debug_event_pb2.TensorDebugMode.FULL_HEALTH,
+        graph_id="abcd",
+        input_tensor_ids=[13, 37],
+        output_tensor_ids=output_tensor_ids,
+        debug_tensor_values=None)
+    self.assertEqual(execution.num_outputs, 0)
+
   def testDebuggedDeviceToJons(self):
     debugged_device = debug_events_reader.DebuggedDevice("/TPU:3", 4)
     self.assertEqual(debugged_device.to_json(), {
@@ -697,6 +713,24 @@ class DataObjectsTest(test_util.TensorFlowTestCase):
             "inner_graph_ids": ["c2d3", "c2d3e4"],
         })
 
+  @parameterized.named_parameters(
+      ("EmptyList", []),
+      ("None", None),
+  )
+  def testGraphOpDigestWithNoOutpusReturnsNumOutputsZero(
+      self, output_tensor_ids):
+    op_creation_digest = debug_events_reader.GraphOpCreationDigest(
+        1234,
+        5678,
+        "deadbeef",
+        "FooOp",
+        "Model_1/Foo_2",
+        output_tensor_ids,
+        "machine.cluster", ("a1", "a2"),
+        input_names=None,
+        device_name=None)
+    self.assertEqual(op_creation_digest.num_outputs, 0)
+
   def testGraphOpCreationDigestNoInputNoDeviceNameToJson(self):
     op_creation_digest = debug_events_reader.GraphOpCreationDigest(
         1234,