Fix merging with message-valued oneof

If messages A and B have the same oneof case, which is a message
type, and we merge B into A, those sub-messages should be merged.

Fixes #3200.

Note that I haven't regenerated all the code, as some of the protos
have been changed, breaking generation.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/google/protobuf/compiler/csharp/csharp_message_field.cc b/src/google/protobuf/compiler/csharp/csharp_message_field.cc
index 438f3102..59b7edfb 100644
--- a/src/google/protobuf/compiler/csharp/csharp_message_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_message_field.cc
@@ -171,6 +171,14 @@ void MessageOneofFieldGenerator::GenerateMembers(io::Printer* printer) {
     "}\n");
 }
 
+void MessageOneofFieldGenerator::GenerateMergingCode(io::Printer* printer) {
+  printer->Print(variables_, 
+    "if ($property_name$ == null) {\n"
+    "  $property_name$ = new $type_name$();\n"
+    "}\n"
+    "$property_name$.MergeFrom(other.$property_name$);\n");
+}
+
 void MessageOneofFieldGenerator::GenerateParsingCode(io::Printer* printer) {
   // TODO(jonskeet): We may be able to do better than this
   printer->Print(