1 files changed, 16 insertions, 1 deletions
diff --git a/python/google/protobuf/internal/type_checkers.py b/python/google/protobuf/internal/type_checkers.py
index 8d10fbe0..363018ed 100755
--- a/python/google/protobuf/internal/type_checkers.py
+++ b/python/google/protobuf/internal/type_checkers.py
@@ -56,6 +56,8 @@ from google.protobuf import descriptor
 
 _FieldDescriptor = descriptor.FieldDescriptor
 
+def SupportsOpenEnums(field_descriptor):
+  return field_descriptor.containing_type.syntax == "proto3"
 
 def GetTypeChecker(field):
   """Returns a type checker for a message field of the specified types.
@@ -71,7 +73,11 @@ def GetTypeChecker(field):
       field.type == _FieldDescriptor.TYPE_STRING):
     return UnicodeValueChecker()
   if field.cpp_type == _FieldDescriptor.CPPTYPE_ENUM:
-    return EnumValueChecker(field.enum_type)
+    if SupportsOpenEnums(field):
+      # When open enums are supported, any int32 can be assigned.
+      return _VALUE_CHECKERS[_FieldDescriptor.CPPTYPE_INT32]
+    else:
+      return EnumValueChecker(field.enum_type)
   return _VALUE_CHECKERS[field.cpp_type]
 
 
@@ -120,6 +126,9 @@ class IntValueChecker(object):
     proposed_value = self._TYPE(proposed_value)
     return proposed_value
 
+  def DefaultValue(self):
+    return 0
+
 
 class EnumValueChecker(object):
 
@@ -137,6 +146,9 @@ class EnumValueChecker(object):
       raise ValueError('Unknown enum value: %d' % proposed_value)
     return proposed_value
 
+  def DefaultValue(self):
+    return self._enum_type.values[0].number
+
 
 class UnicodeValueChecker(object):
 
@@ -162,6 +174,9 @@ class UnicodeValueChecker(object):
                          (proposed_value))
     return proposed_value
 
+  def DefaultValue(self):
+    return u""
+
 
 class Int32ValueChecker(IntValueChecker):
   # We're sure to use ints instead of longs here since comparison may be more