Integrated internal changes from Google

9 files changed, 196 insertions, 53 deletions

diff --git a/python/google/protobuf/internal/_parameterized.py b/python/google/protobuf/internal/_parameterized.py
index 23a78f03..f2c0b305 100755
--- a/python/google/protobuf/internal/_parameterized.py
+++ b/python/google/protobuf/internal/_parameterized.py
@@ -37,8 +37,8 @@ argument tuples.
 
 A simple example:
 
-  class AdditionExample(parameterized.ParameterizedTestCase):
-    @parameterized.Parameters(
+  class AdditionExample(parameterized.TestCase):
+    @parameterized.parameters(
        (1, 2, 3),
        (4, 5, 9),
        (1, 1, 3))
@@ -54,8 +54,8 @@ fail due to an assertion error (1 + 1 != 3).
 Parameters for invididual test cases can be tuples (with positional parameters)
 or dictionaries (with named parameters):
 
-  class AdditionExample(parameterized.ParameterizedTestCase):
-    @parameterized.Parameters(
+  class AdditionExample(parameterized.TestCase):
+    @parameterized.parameters(
        {'op1': 1, 'op2': 2, 'result': 3},
        {'op1': 4, 'op2': 5, 'result': 9},
     )
@@ -77,13 +77,13 @@ stay the same across several invocations, object representations like
   '<__main__.Foo object at 0x23d8610>'
 
 are turned into '<__main__.Foo>'. For even more descriptive names,
-especially in test logs, you can use the NamedParameters decorator. In
+especially in test logs, you can use the named_parameters decorator. In
 this case, only tuples are supported, and the first parameters has to
 be a string (or an object that returns an apt name when converted via
 str()):
 
-  class NamedExample(parameterized.ParameterizedTestCase):
-    @parameterized.NamedParameters(
+  class NamedExample(parameterized.TestCase):
+    @parameterized.named_parameters(
        ('Normal', 'aa', 'aaa', True),
        ('EmptyPrefix', '', 'abc', True),
        ('BothEmpty', '', '', True))
@@ -103,13 +103,13 @@ from the command line:
 Parameterized Classes
 =====================
 If invocation arguments are shared across test methods in a single
-ParameterizedTestCase class, instead of decorating all test methods
+TestCase class, instead of decorating all test methods
 individually, the class itself can be decorated:
 
-  @parameterized.Parameters(
+  @parameterized.parameters(
     (1, 2, 3)
     (4, 5, 9))
-  class ArithmeticTest(parameterized.ParameterizedTestCase):
+  class ArithmeticTest(parameterized.TestCase):
     def testAdd(self, arg1, arg2, result):
       self.assertEqual(arg1 + arg2, result)
 
@@ -122,8 +122,8 @@ If parameters should be shared across several test cases, or are dynamically
 created from other sources, a single non-tuple iterable can be passed into
 the decorator. This iterable will be used to obtain the test cases:
 
-  class AdditionExample(parameterized.ParameterizedTestCase):
-    @parameterized.Parameters(
+  class AdditionExample(parameterized.TestCase):
+    @parameterized.parameters(
       c.op1, c.op2, c.result for c in testcases
     )
     def testAddition(self, op1, op2, result):
@@ -135,8 +135,8 @@ Single-Argument Test Methods
 If a test method takes only one argument, the single argument does not need to
 be wrapped into a tuple:
 
-  class NegativeNumberExample(parameterized.ParameterizedTestCase):
-    @parameterized.Parameters(
+  class NegativeNumberExample(parameterized.TestCase):
+    @parameterized.parameters(
        -1, -3, -4, -5
     )
     def testIsNegative(self, arg):
@@ -212,7 +212,7 @@ class _ParameterizedTestIter(object):
   def __call__(self, *args, **kwargs):
     raise RuntimeError('You appear to be running a parameterized test case '
                        'without having inherited from parameterized.'
-                       'ParameterizedTestCase. This is bad because none of '
+                       'TestCase. This is bad because none of '
                        'your test cases are actually being run.')
 
   def __iter__(self):
@@ -306,7 +306,7 @@ def _ParameterDecorator(naming_type, testcases):
   return _Apply
 
 
-def Parameters(*testcases):
+def parameters(*testcases):  # pylint: disable=invalid-name
   """A decorator for creating parameterized tests.
 
   See the module docstring for a usage example.
@@ -321,7 +321,7 @@ def Parameters(*testcases):
   return _ParameterDecorator(_ARGUMENT_REPR, testcases)
 
 
-def NamedParameters(*testcases):
+def named_parameters(*testcases):  # pylint: disable=invalid-name
   """A decorator for creating parameterized tests.
 
   See the module docstring for a usage example. The first element of
@@ -348,7 +348,7 @@ class TestGeneratorMetaclass(type):
   up as tests by the unittest framework.
 
   In general, it is supposed to be used in conjunction with the
-  Parameters decorator.
+  parameters decorator.
   """
 
   def __new__(mcs, class_name, bases, dct):
@@ -385,8 +385,8 @@ def _UpdateClassDictForParamTestCase(dct, id_suffix, name, iterator):
     id_suffix[new_name] = getattr(func, '__x_extra_id__', '')
 
 
-class ParameterizedTestCase(unittest.TestCase):
-  """Base class for test cases using the Parameters decorator."""
+class TestCase(unittest.TestCase):
+  """Base class for test cases using the parameters decorator."""
   __metaclass__ = TestGeneratorMetaclass
 
   def _OriginalName(self):
@@ -409,10 +409,10 @@ class ParameterizedTestCase(unittest.TestCase):
                         self._id_suffix.get(self._testMethodName, ''))
 
 
-def CoopParameterizedTestCase(other_base_class):
+def CoopTestCase(other_base_class):
   """Returns a new base class with a cooperative metaclass base.
 
-  This enables the ParameterizedTestCase to be used in combination
+  This enables the TestCase to be used in combination
   with other base classes that have custom metaclasses, such as
   mox.MoxTestBase.
 
@@ -425,7 +425,7 @@ def CoopParameterizedTestCase(other_base_class):
 
     from google3.testing.pybase import parameterized
 
-    class ExampleTest(parameterized.CoopParameterizedTestCase(mox.MoxTestBase)):
+    class ExampleTest(parameterized.CoopTestCase(mox.MoxTestBase)):
       ...
 
   Args:
@@ -439,5 +439,5 @@ def CoopParameterizedTestCase(other_base_class):
       (other_base_class.__metaclass__,
        TestGeneratorMetaclass), {})
   return metaclass(
-      'CoopParameterizedTestCase',
-      (other_base_class, ParameterizedTestCase), {})
+      'CoopTestCase',
+      (other_base_class, TestCase), {})
diff --git a/python/google/protobuf/internal/api_implementation.py b/python/google/protobuf/internal/api_implementation.py
index 553fcdb6..ab9e7812 100755
--- a/python/google/protobuf/internal/api_implementation.py
+++ b/python/google/protobuf/internal/api_implementation.py
@@ -66,10 +66,13 @@ if _api_version < 0:  # Still unspecified?
       from google.protobuf.internal import use_pure_python
       del use_pure_python  # Avoids a pylint error and namespace pollution.
     except ImportError:
-      if _proto_extension_modules_exist_in_build:
-        if sys.version_info[0] >= 3:  # Python 3 defaults to C++ impl v2.
-          _api_version = 2
-          # TODO(b/17427486): Make Python 2 default to C++ impl v2.
+      # TODO(b/74017912): It's unsafe to enable :use_fast_cpp_protos by default;
+      # it can cause data loss if you have any Python-only extensions to any
+      # message passed back and forth with C++ code.
+      #
+      # TODO(b/17427486): Once that bug is fixed, we want to make both Python 2
+      # and Python 3 default to `_api_version = 2` (C++ implementation V2).
+      pass
 
 _default_implementation_type = (
     'python' if _api_version <= 0 else 'cpp')
diff --git a/python/google/protobuf/internal/encoder.py b/python/google/protobuf/internal/encoder.py
index dc7a8ce8..0d1f49dd 100755
--- a/python/google/protobuf/internal/encoder.py
+++ b/python/google/protobuf/internal/encoder.py
@@ -372,7 +372,7 @@ def MapSizer(field_descriptor, is_message_map):
 def _VarintEncoder():
   """Return an encoder for a basic varint value (does not include tag)."""
 
-  def EncodeVarint(write, value, unused_deterministic):
+  def EncodeVarint(write, value, unused_deterministic=None):
     bits = value & 0x7f
     value >>= 7
     while value:
@@ -388,7 +388,7 @@ def _SignedVarintEncoder():
   """Return an encoder for a basic signed varint value (does not include
   tag)."""
 
-  def EncodeSignedVarint(write, value, unused_deterministic):
+  def EncodeSignedVarint(write, value, unused_deterministic=None):
     if value < 0:
       value += (1 << 64)
     bits = value & 0x7f
@@ -524,14 +524,14 @@ def _StructPackEncoder(wire_type, format):
       return EncodePackedField
     elif is_repeated:
       tag_bytes = TagBytes(field_number, wire_type)
-      def EncodeRepeatedField(write, value, unused_deterministic):
+      def EncodeRepeatedField(write, value, unused_deterministic=None):
         for element in value:
           write(tag_bytes)
           write(local_struct_pack(format, element))
       return EncodeRepeatedField
     else:
       tag_bytes = TagBytes(field_number, wire_type)
-      def EncodeField(write, value, unused_deterministic):
+      def EncodeField(write, value, unused_deterministic=None):
         write(tag_bytes)
         return write(local_struct_pack(format, value))
       return EncodeField
@@ -595,7 +595,7 @@ def _FloatingPointEncoder(wire_type, format):
       return EncodePackedField
     elif is_repeated:
       tag_bytes = TagBytes(field_number, wire_type)
-      def EncodeRepeatedField(write, value, unused_deterministic):
+      def EncodeRepeatedField(write, value, unused_deterministic=None):
         for element in value:
           write(tag_bytes)
           try:
@@ -605,7 +605,7 @@ def _FloatingPointEncoder(wire_type, format):
       return EncodeRepeatedField
     else:
       tag_bytes = TagBytes(field_number, wire_type)
-      def EncodeField(write, value, unused_deterministic):
+      def EncodeField(write, value, unused_deterministic=None):
         write(tag_bytes)
         try:
           write(local_struct_pack(format, value))
@@ -662,7 +662,7 @@ def BoolEncoder(field_number, is_repeated, is_packed):
     return EncodePackedField
   elif is_repeated:
     tag_bytes = TagBytes(field_number, wire_format.WIRETYPE_VARINT)
-    def EncodeRepeatedField(write, value, unused_deterministic):
+    def EncodeRepeatedField(write, value, unused_deterministic=None):
       for element in value:
         write(tag_bytes)
         if element:
@@ -672,7 +672,7 @@ def BoolEncoder(field_number, is_repeated, is_packed):
     return EncodeRepeatedField
   else:
     tag_bytes = TagBytes(field_number, wire_format.WIRETYPE_VARINT)
-    def EncodeField(write, value, unused_deterministic):
+    def EncodeField(write, value, unused_deterministic=None):
       write(tag_bytes)
       if value:
         return write(true_byte)
diff --git a/python/google/protobuf/internal/json_format_test.py b/python/google/protobuf/internal/json_format_test.py
index 19182b7f..d891dce1 100644
--- a/python/google/protobuf/internal/json_format_test.py
+++ b/python/google/protobuf/internal/json_format_test.py
@@ -983,6 +983,18 @@ class JsonFormatTest(JsonFormatBase):
     self.assertEqual('{\n"int32Value": 12345\n}',
                      json_format.MessageToJson(message, indent=0))
 
+  def testFormatEnumsAsInts(self):
+    message = json_format_proto3_pb2.TestMessage()
+    message.enum_value = json_format_proto3_pb2.BAR
+    message.repeated_enum_value.append(json_format_proto3_pb2.FOO)
+    message.repeated_enum_value.append(json_format_proto3_pb2.BAR)
+    self.assertEqual(json.loads('{\n'
+                                '  "enumValue": 1,\n'
+                                '  "repeatedEnumValue": [0, 1]\n'
+                                '}\n'),
+                     json.loads(json_format.MessageToJson(
+                         message, use_integers_for_enums=True)))
+
   def testParseDict(self):
     expected = 12345
     js_dict = {'int32Value': expected}
diff --git a/python/google/protobuf/internal/message_test.py b/python/google/protobuf/internal/message_test.py
index 8dae6377..61a56a67 100755
--- a/python/google/protobuf/internal/message_test.py
+++ b/python/google/protobuf/internal/message_test.py
@@ -99,7 +99,7 @@ def IsNegInf(val):
 BaseTestCase = testing_refleaks.BaseTestCase
 
 
-@_parameterized.NamedParameters(
+@_parameterized.named_parameters(
     ('_proto2', unittest_pb2),
     ('_proto3', unittest_proto3_arena_pb2))
 class MessageTest(BaseTestCase):
@@ -1694,6 +1694,33 @@ class Proto3Test(BaseTestCase):
     with self.assertRaises(TypeError):
       del msg2.map_int32_foreign_message['']
 
+  def testMapMergeFrom(self):
+    msg = map_unittest_pb2.TestMap()
+    msg.map_int32_int32[12] = 34
+    msg.map_int32_int32[56] = 78
+    msg.map_int64_int64[22] = 33
+    msg.map_int32_foreign_message[111].c = 5
+    msg.map_int32_foreign_message[222].c = 10
+
+    msg2 = map_unittest_pb2.TestMap()
+    msg2.map_int32_int32[12] = 55
+    msg2.map_int64_int64[88] = 99
+    msg2.map_int32_foreign_message[222].c = 15
+    msg2.map_int32_foreign_message[222].d = 20
+
+    msg2.map_int32_int32.MergeFrom(msg.map_int32_int32)
+    self.assertEqual(34, msg2.map_int32_int32[12])
+    self.assertEqual(78, msg2.map_int32_int32[56])
+
+    msg2.map_int64_int64.MergeFrom(msg.map_int64_int64)
+    self.assertEqual(33, msg2.map_int64_int64[22])
+    self.assertEqual(99, msg2.map_int64_int64[88])
+
+    msg2.map_int32_foreign_message.MergeFrom(msg.map_int32_foreign_message)
+    self.assertEqual(5, msg2.map_int32_foreign_message[111].c)
+    self.assertEqual(10, msg2.map_int32_foreign_message[222].c)
+    self.assertFalse(msg2.map_int32_foreign_message[222].HasField('d'))
+
   def testMergeFromBadType(self):
     msg = map_unittest_pb2.TestMap()
     with self.assertRaisesRegexp(
diff --git a/python/google/protobuf/internal/no_package.proto b/python/google/protobuf/internal/no_package.proto
new file mode 100644
index 00000000..f6d26735
--- /dev/null
+++ b/python/google/protobuf/internal/no_package.proto
@@ -0,0 +1,12 @@
+syntax = "proto2";
+
+option py_api_version = 2;
+
+enum NoPackageEnum {
+  NO_PACKAGE_VALUE_0 = 0;
+  NO_PACKAGE_VALUE_1 = 1;
+}
+
+message NoPackageMessage {
+  optional NoPackageEnum no_package_enum = 1;
+}
\ No newline at end of file
diff --git a/python/google/protobuf/internal/text_format_test.py b/python/google/protobuf/internal/text_format_test.py
index ed3445f2..237a2d50 100755
--- a/python/google/protobuf/internal/text_format_test.py
+++ b/python/google/protobuf/internal/text_format_test.py
@@ -48,6 +48,7 @@ except ImportError:
 
 from google.protobuf.internal import _parameterized
 
+from google.protobuf import any_pb2
 from google.protobuf import any_test_pb2
 from google.protobuf import map_unittest_pb2
 from google.protobuf import unittest_mset_pb2
@@ -99,7 +100,7 @@ class TextFormatBase(unittest.TestCase):
     return text
 
 
-@_parameterized.Parameters((unittest_pb2), (unittest_proto3_arena_pb2))
+@_parameterized.parameters((unittest_pb2), (unittest_proto3_arena_pb2))
 class TextFormatTest(TextFormatBase):
 
   def testPrintExotic(self, message_module):
@@ -369,6 +370,7 @@ class TextFormatTest(TextFormatBase):
   def testParseRepeatedScalarShortFormat(self, message_module):
     message = message_module.TestAllTypes()
     text = ('repeated_int64: [100, 200];\n'
+            'repeated_int64: []\n'
             'repeated_int64: 300,\n'
             'repeated_string: ["one", "two"];\n')
     text_format.Parse(text, message)
@@ -524,20 +526,68 @@ class OnlyWorksWithProto2RightNowTests(TextFormatBase):
 
   def testPrintInIndexOrder(self):
     message = unittest_pb2.TestFieldOrderings()
-    message.my_string = '115'
+    # Fields are listed in index order instead of field number.
+    message.my_string = 'str'
     message.my_int = 101
     message.my_float = 111
     message.optional_nested_message.oo = 0
     message.optional_nested_message.bb = 1
+    message.Extensions[unittest_pb2.my_extension_string] = 'ext_str0'
+    # Extensions are listed based on the order of extension number.
+    # Extension number 12.
+    message.Extensions[unittest_pb2.TestExtensionOrderings2.
+                       test_ext_orderings2].my_string = 'ext_str2'
+    # Extension number 13.
+    message.Extensions[unittest_pb2.TestExtensionOrderings1.
+                       test_ext_orderings1].my_string = 'ext_str1'
+    # Extension number 14.
+    message.Extensions[
+        unittest_pb2.TestExtensionOrderings2.TestExtensionOrderings3.
+        test_ext_orderings3].my_string = 'ext_str3'
+
+    # Print in index order.
     self.CompareToGoldenText(
-        self.RemoveRedundantZeros(text_format.MessageToString(
-            message, use_index_order=True)),
-        'my_string: \"115\"\nmy_int: 101\nmy_float: 111\n'
-        'optional_nested_message {\n  oo: 0\n  bb: 1\n}\n')
+        self.RemoveRedundantZeros(
+            text_format.MessageToString(message, use_index_order=True)),
+        'my_string: "str"\n'
+        'my_int: 101\n'
+        'my_float: 111\n'
+        'optional_nested_message {\n'
+        '  oo: 0\n'
+        '  bb: 1\n'
+        '}\n'
+        '[protobuf_unittest.TestExtensionOrderings2.test_ext_orderings2] {\n'
+        '  my_string: "ext_str2"\n'
+        '}\n'
+        '[protobuf_unittest.TestExtensionOrderings1.test_ext_orderings1] {\n'
+        '  my_string: "ext_str1"\n'
+        '}\n'
+        '[protobuf_unittest.TestExtensionOrderings2.TestExtensionOrderings3'
+        '.test_ext_orderings3] {\n'
+        '  my_string: "ext_str3"\n'
+        '}\n'
+        '[protobuf_unittest.my_extension_string]: "ext_str0"\n')
+    # By default, print in field number order.
     self.CompareToGoldenText(
         self.RemoveRedundantZeros(text_format.MessageToString(message)),
-        'my_int: 101\nmy_string: \"115\"\nmy_float: 111\n'
-        'optional_nested_message {\n  bb: 1\n  oo: 0\n}\n')
+        'my_int: 101\n'
+        'my_string: "str"\n'
+        '[protobuf_unittest.TestExtensionOrderings2.test_ext_orderings2] {\n'
+        '  my_string: "ext_str2"\n'
+        '}\n'
+        '[protobuf_unittest.TestExtensionOrderings1.test_ext_orderings1] {\n'
+        '  my_string: "ext_str1"\n'
+        '}\n'
+        '[protobuf_unittest.TestExtensionOrderings2.TestExtensionOrderings3'
+        '.test_ext_orderings3] {\n'
+        '  my_string: "ext_str3"\n'
+        '}\n'
+        '[protobuf_unittest.my_extension_string]: "ext_str0"\n'
+        'my_float: 111\n'
+        'optional_nested_message {\n'
+        '  bb: 1\n'
+        '  oo: 0\n'
+        '}\n')
 
   def testMergeLinesGolden(self):
     opened = self.ReadGolden('text_format_unittest_data_oneof_implemented.txt')
@@ -970,15 +1020,26 @@ class Proto2Tests(TextFormatBase):
         '"protobuf_unittest.optional_int32_extension" extensions.'),
                           text_format.Parse, text, message)
 
-  def testParseDuplicateNestedMessageScalars(self):
+  def testParseDuplicateMessages(self):
     message = unittest_pb2.TestAllTypes()
     text = ('optional_nested_message { bb: 1 } '
             'optional_nested_message { bb: 2 }')
     six.assertRaisesRegex(self, text_format.ParseError, (
-        '1:65 : Message type "protobuf_unittest.TestAllTypes.NestedMessage" '
-        'should not have multiple "bb" fields.'), text_format.Parse, text,
+        '1:59 : Message type "protobuf_unittest.TestAllTypes" '
+        'should not have multiple "optional_nested_message" fields.'),
+                          text_format.Parse, text,
                           message)
 
+  def testParseDuplicateExtensionMessages(self):
+    message = unittest_pb2.TestAllExtensions()
+    text = ('[protobuf_unittest.optional_nested_message_extension]: {} '
+            '[protobuf_unittest.optional_nested_message_extension]: {}')
+    six.assertRaisesRegex(self, text_format.ParseError, (
+        '1:114 : Message type "protobuf_unittest.TestAllExtensions" '
+        'should not have multiple '
+        '"protobuf_unittest.optional_nested_message_extension" extensions.'),
+                          text_format.Parse, text, message)
+
   def testParseDuplicateScalars(self):
     message = unittest_pb2.TestAllTypes()
     text = ('optional_int32: 42 ' 'optional_int32: 67')
@@ -1065,6 +1126,14 @@ class Proto3Tests(unittest.TestCase):
         '  }\n'
         '}\n')
 
+  def testTopAnyMessage(self):
+    packed_msg = unittest_pb2.OneString()
+    msg = any_pb2.Any()
+    msg.Pack(packed_msg)
+    text = text_format.MessageToString(msg)
+    other_msg = text_format.Parse(text, any_pb2.Any())
+    self.assertEqual(msg, other_msg)
+
   def testPrintMessageExpandAnyRepeated(self):
     packed_message = unittest_pb2.OneString()
     message = any_test_pb2.TestAny()
@@ -1489,7 +1558,7 @@ class TokenizerTest(unittest.TestCase):
 
 
 # Tests for pretty printer functionality.
-@_parameterized.Parameters((unittest_pb2), (unittest_proto3_arena_pb2))
+@_parameterized.parameters((unittest_pb2), (unittest_proto3_arena_pb2))
 class PrettyPrinterTest(TextFormatBase):
 
   def testPrettyPrintNoMatch(self, message_module):
diff --git a/python/google/protobuf/internal/well_known_types.py b/python/google/protobuf/internal/well_known_types.py
index 3573770b..37a65cfa 100644
--- a/python/google/protobuf/internal/well_known_types.py
+++ b/python/google/protobuf/internal/well_known_types.py
@@ -375,6 +375,9 @@ def _CheckDurationValid(seconds, nanos):
     raise Error(
         'Duration is not valid: Nanos {0} must be in range '
         '[-999999999, 999999999].'.format(nanos))
+  if (nanos < 0 and seconds > 0) or (nanos > 0 and seconds < 0):
+    raise Error(
+        'Duration is not valid: Sign mismatch.')
 
 
 def _RoundTowardZero(value, divider):
@@ -649,9 +652,10 @@ def _MergeMessage(
         raise ValueError('Error: Field {0} in message {1} is not a singular '
                          'message field and cannot have sub-fields.'.format(
                              name, source_descriptor.full_name))
-      _MergeMessage(
-          child, getattr(source, name), getattr(destination, name),
-          replace_message, replace_repeated)
+      if source.HasField(name):
+        _MergeMessage(
+            child, getattr(source, name), getattr(destination, name),
+            replace_message, replace_repeated)
       continue
     if field.label == FieldDescriptor.LABEL_REPEATED:
       if replace_repeated:
diff --git a/python/google/protobuf/internal/well_known_types_test.py b/python/google/protobuf/internal/well_known_types_test.py
index 573bc37d..965940b2 100644
--- a/python/google/protobuf/internal/well_known_types_test.py
+++ b/python/google/protobuf/internal/well_known_types_test.py
@@ -345,6 +345,12 @@ class TimeUtilTest(TimeUtilTestBase):
         r'Duration is not valid\: Nanos 1000000000 must be in range'
         r' \[-999999999\, 999999999\].',
         message.ToJsonString)
+    message.seconds = -1
+    message.nanos = 1
+    self.assertRaisesRegexp(
+        well_known_types.Error,
+        r'Duration is not valid\: Sign mismatch.',
+        message.ToJsonString)
 
 
 class FieldMaskTest(unittest.TestCase):
@@ -599,6 +605,16 @@ class FieldMaskTest(unittest.TestCase):
     self.assertEqual(1, len(nested_dst.payload.repeated_int32))
     self.assertEqual(1234, nested_dst.payload.repeated_int32[0])
 
+    # Test Merge oneof field.
+    new_msg = unittest_pb2.TestOneof2()
+    dst = unittest_pb2.TestOneof2()
+    dst.foo_message.qux_int = 1
+    mask = field_mask_pb2.FieldMask()
+    mask.FromJsonString('fooMessage,fooLazyMessage.quxInt')
+    mask.MergeMessage(new_msg, dst)
+    self.assertTrue(dst.HasField('foo_message'))
+    self.assertFalse(dst.HasField('foo_lazy_message'))
+
   def testMergeErrors(self):
     src = unittest_pb2.TestAllTypes()
     dst = unittest_pb2.TestAllTypes()