1# Copyright 2017 The TensorFlow Authors. All Rights Reserved.
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7#     http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12# See the License for the specific language governing permissions and
13# limitations under the License.
14# ==============================================================================
15"""Various context managers."""
16
17from __future__ import absolute_import
18from __future__ import division
19from __future__ import print_function
20
21import contextlib
22
23from tensorflow.python.framework import ops
24from tensorflow.python.ops import tensor_array_ops
25
26
27def control_dependency_on_returns(return_value):
28  """Create a TF control dependency on the return values of a function.
29
30  If the function had no return value, a no-op context is returned.
31
32  Args:
33    return_value: The return value to set as control dependency.
34
35  Returns:
36    A context manager.
37  """
38  def control_dependency_handle(t):
39    if isinstance(t, tensor_array_ops.TensorArray):
40      return t.flow
41    return t
42
43  if return_value is None:
44    return contextlib.contextmanager(lambda: (yield))()
45  # TODO(mdan): Filter to tensor objects.
46  if not isinstance(return_value, (list, tuple)):
47    return_value = (return_value,)
48  return_value = tuple(control_dependency_handle(t) for t in return_value)
49  return ops.control_dependencies(return_value)
50