Continue to allow flag access before explicit parse.

Made tf.flags.FLAGS a wrapper of absl.flags.FLAGS, when the flag is access, parse flags implicitly with sys.argv if not yet.

PiperOrigin-RevId: 179068530

2 files changed, 110 insertions, 2 deletions

diff --git a/tensorflow/python/platform/flags.py b/tensorflow/python/platform/flags.py
index abd6f3d855..6225db7744 100644
--- a/tensorflow/python/platform/flags.py
+++ b/tensorflow/python/platform/flags.py
@@ -19,6 +19,7 @@ from __future__ import division
 from __future__ import print_function
 
 import logging as _logging
+import sys as _sys
 
 # go/tf-wildcard-import
 from absl.flags import *  # pylint: disable=wildcard-import
@@ -59,6 +60,58 @@ def _wrap_define_function(original_function):
   return tf_decorator.make_decorator(original_function, wrapper)
 
 
+class _FlagValuesWrapper(object):
+  """Wrapper class for absl.flags.FLAGS.
+
+  The difference is that tf.flags.FLAGS implicitly parses flags with sys.argv
+  when accessing the FLAGS values before it's explicitly parsed,
+  while absl.flags.FLAGS raises an exception.
+  """
+
+  def __init__(self, flags_object):
+    self.__dict__['__wrapped'] = flags_object
+
+  def __getattribute__(self, name):
+    if name == '__dict__':
+      return super(_FlagValuesWrapper, self).__getattribute__(name)
+    return self.__dict__['__wrapped'].__getattribute__(name)
+
+  def __getattr__(self, name):
+    wrapped = self.__dict__['__wrapped']
+    # To maintain backwards compatibility, implicitly parse flags when reading
+    # a flag.
+    if not wrapped.is_parsed():
+      wrapped(_sys.argv)
+    return wrapped.__getattr__(name)
+
+  def __setattr__(self, name, value):
+    return self.__dict__['__wrapped'].__setattr__(name, value)
+
+  def __delattr__(self, name):
+    return self.__dict__['__wrapped'].__delattr__(name)
+
+  def __dir__(self):
+    return self.__dict__['__wrapped'].__dir__()
+
+  def __getitem__(self, name):
+    return self.__dict__['__wrapped'].__getitem__(name)
+
+  def __setitem__(self, name, flag):
+    return self.__dict__['__wrapped'].__setitem__(name, flag)
+
+  def __len__(self):
+    return self.__dict__['__wrapped'].__len__()
+
+  def __iter__(self):
+    return self.__dict__['__wrapped'].__iter__()
+
+  def __str__(self):
+    return self.__dict__['__wrapped'].__str__()
+
+  def __call__(self, *args, **kwargs):
+    return self.__dict__['__wrapped'].__call__(*args, **kwargs)
+
+
 # pylint: disable=invalid-name,used-before-assignment
 # absl.flags APIs use `default` as the name of the default value argument.
 # Allow the following functions continue to accept `default_value`.
@@ -68,3 +121,5 @@ DEFINE_bool = DEFINE_boolean
 DEFINE_float = _wrap_define_function(DEFINE_float)
 DEFINE_integer = _wrap_define_function(DEFINE_integer)
 # pylint: enable=invalid-name,used-before-assignment
+
+FLAGS = _FlagValuesWrapper(FLAGS)  # pylint: disable=used-before-assignment
diff --git a/tensorflow/python/platform/flags_test.py b/tensorflow/python/platform/flags_test.py
index e8200142dd..bd3c8e3995 100644
--- a/tensorflow/python/platform/flags_test.py
+++ b/tensorflow/python/platform/flags_test.py
@@ -17,11 +17,13 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
+import sys
 import unittest
 
 from absl import flags as absl_flags
 
 from tensorflow.python.platform import flags
+from tensorflow.python.platform import test
 
 
 flags.DEFINE_string(
@@ -48,8 +50,59 @@ flags.DEFINE_boolean(
 
 class FlagsTest(unittest.TestCase):
 
-  def test_global_flags_object(self):
-    self.assertIs(flags.FLAGS, absl_flags.FLAGS)
+  def setUp(self):
+    self.original_flags = flags.FlagValues()
+    self.wrapped_flags = flags._FlagValuesWrapper(self.original_flags)
+    flags.DEFINE_string(
+        'test', 'default', 'test flag', flag_values=self.wrapped_flags)
+
+  def test_attribute_overrides(self):
+    # Test that methods defined in absl.flags.FlagValues are the same as the
+    # wrapped ones.
+    self.assertEqual(flags.FLAGS.is_parsed, absl_flags.FLAGS.is_parsed)
+
+  def test_getattr(self):
+    self.assertFalse(self.wrapped_flags.is_parsed())
+    with test.mock.patch.object(sys, 'argv', new=['program', '--test=new']):
+      self.assertEqual('new', self.wrapped_flags.test)
+    self.assertTrue(self.wrapped_flags.is_parsed())
+
+  def test_setattr(self):
+    self.assertEqual('default', self.wrapped_flags.test)
+    self.wrapped_flags.test = 'new'
+    self.assertEqual('new', self.wrapped_flags.test)
+
+  def test_delattr(self):
+    del self.wrapped_flags.test
+    self.assertNotIn('test', self.wrapped_flags)
+    with self.assertRaises(AttributeError):
+      _ = self.wrapped_flags.test
+
+  def test_dir(self):
+    self.assertEqual(['test'], dir(self.wrapped_flags))
+
+  def test_getitem(self):
+    self.assertIs(self.original_flags['test'], self.wrapped_flags['test'])
+
+  def test_setitem(self):
+    flag = flags.Flag(flags.ArgumentParser(), flags.ArgumentSerializer(),
+                      'fruit', 'apple', 'the fruit type')
+    self.wrapped_flags['fruit'] = flag
+    self.assertIs(self.original_flags['fruit'], self.wrapped_flags['fruit'])
+    self.assertEqual('apple', self.wrapped_flags.fruit)
+
+  def test_len(self):
+    self.assertEqual(1, len(self.wrapped_flags))
+
+  def test_iter(self):
+    self.assertEqual(['test'], list(self.wrapped_flags))
+
+  def test_str(self):
+    self.assertEqual(str(self.wrapped_flags), str(self.original_flags))
+
+  def test_call(self):
+    self.wrapped_flags(['program', '--test=new'])
+    self.assertEqual('new', self.wrapped_flags.test)
 
   def test_keyword_arguments(self):
     test_cases = (