C# generator: Append _ to the oneof case enum name if it's "None"

Fixes #9605 (tests in next commit)

src/google/protobuf/compiler/csharp/csharp_enum_field.cc

@@ -109,7 +109,7 @@ void EnumOneofFieldGenerator::GenerateParsingCode(io::Printer* printer) {
   printer->Print(
     variables_,
     "$oneof_name$_ = input.ReadEnum();\n"
-    "$oneof_name$Case_ = $oneof_property_name$OneofCase.$property_name$;\n");
+    "$oneof_name$Case_ = $oneof_property_name$OneofCase.$oneof_case_name$;\n");
 }
 
 void EnumOneofFieldGenerator::GenerateSerializationCode(io::Printer* printer) {

src/google/protobuf/compiler/csharp/csharp_field_base.cc

@@ -130,8 +130,9 @@ void FieldGeneratorBase::SetCommonOneofFieldVariables(
   } else {
     (*variables)["has_property_check"] =
       oneof_name() + "Case_ == " + oneof_property_name() +
-      "OneofCase." + property_name();
+      "OneofCase." + oneof_case_name();
   }
+  (*variables)["oneof_case_name"] = oneof_case_name();
   (*variables)["oneof_property_name"] = oneof_property_name();
 }
 
@@ -187,6 +188,10 @@ void FieldGeneratorBase::AddPublicMemberAttributes(io::Printer* printer) {
   WriteGeneratedCodeAttributes(printer);
 }
 
+std::string FieldGeneratorBase::oneof_case_name() {
+  return GetOneofCaseName(descriptor_);
+}
+
 std::string FieldGeneratorBase::oneof_property_name() {
   return UnderscoresToCamelCase(descriptor_->containing_oneof()->name(), true);
 }

src/google/protobuf/compiler/csharp/csharp_field_base.h

@@ -85,6 +85,7 @@ class FieldGeneratorBase : public SourceGeneratorBase {
       std::map<std::string, std::string>* variables);
 
   std::string oneof_property_name();
+  std::string oneof_case_name(); 
   std::string oneof_name();
   std::string property_name();
   std::string name();

src/google/protobuf/compiler/csharp/csharp_helpers.cc

@@ -393,6 +393,13 @@ std::string GetPropertyName(const FieldDescriptor* descriptor) {
   return property_name;
 }
 
+std::string GetOneofCaseName(const FieldDescriptor* descriptor) {
+  // The name in a oneof case enum is the same as for the property, but as we always have a "None"
+  // value as well, we need to reserve that by appending an underscore.
+  std::string property_name = GetPropertyName(descriptor);
+  return property_name == "None" ? "None_" : property_name;
+}
+
 std::string GetOutputFile(const FileDescriptor* descriptor,
                           const std::string file_extension,
                           const bool generate_directories,

src/google/protobuf/compiler/csharp/csharp_helpers.h

@@ -87,6 +87,8 @@ std::string GetFieldConstantName(const FieldDescriptor* field);
 
 std::string GetPropertyName(const FieldDescriptor* descriptor);
 
+std::string GetOneofCaseName(const FieldDescriptor* descriptor);
+
 int GetFixedSize(FieldDescriptor::Type type);
 
 std::string UnderscoresToCamelCase(const std::string& input,

src/google/protobuf/compiler/csharp/csharp_message.cc

@@ -238,8 +238,8 @@ void MessageGenerator::Generate(io::Printer* printer) {
     printer->Print("None = 0,\n");
     for (int j = 0; j < oneof->field_count(); j++) {
       const FieldDescriptor* field = oneof->field(j);
-      printer->Print("$field_property_name$ = $index$,\n",
-                     "field_property_name", GetPropertyName(field),
+      printer->Print("$oneof_case_name$ = $index$,\n",
+                     "oneof_case_name", GetOneofCaseName(field),
                      "index", StrCat(field->number()));
     }
     printer->Outdent();
@@ -403,10 +403,10 @@ void MessageGenerator::GenerateCloningCode(io::Printer* printer) {
     for (int j = 0; j < oneof->field_count(); j++) {
       const FieldDescriptor* field = oneof->field(j);
       std::unique_ptr<FieldGeneratorBase> generator(CreateFieldGeneratorInternal(field));
-      vars["field_property_name"] = GetPropertyName(field);
+      vars["oneof_case_name"] = GetOneofCaseName(field);
       printer->Print(
           vars,
-          "case $property_name$OneofCase.$field_property_name$:\n");
+          "case $property_name$OneofCase.$oneof_case_name$:\n");
       printer->Indent();
       generator->GenerateCloningCode(printer);
       printer->Print("break;\n");
@@ -635,10 +635,10 @@ void MessageGenerator::GenerateMergingMethods(io::Printer* printer) {
     printer->Indent();
     for (int j = 0; j < oneof->field_count(); j++) {
       const FieldDescriptor* field = oneof->field(j);
-      vars["field_property_name"] = GetPropertyName(field);
+      vars["oneof_case_name"] = GetOneofCaseName(field);
       printer->Print(
         vars,
-        "case $property_name$OneofCase.$field_property_name$:\n");
+        "case $property_name$OneofCase.$oneof_case_name$:\n");
       printer->Indent();
       std::unique_ptr<FieldGeneratorBase> generator(CreateFieldGeneratorInternal(field));
       generator->GenerateMergingCode(printer);

src/google/protobuf/compiler/csharp/csharp_message_field.cc

@@ -225,7 +225,7 @@ void MessageOneofFieldGenerator::GenerateMembers(io::Printer* printer) {
     "  get { return $has_property_check$ ? ($type_name$) $oneof_name$_ : null; }\n"
     "  set {\n"
     "    $oneof_name$_ = value;\n"
-    "    $oneof_name$Case_ = value == null ? $oneof_property_name$OneofCase.None : $oneof_property_name$OneofCase.$property_name$;\n"
+    "    $oneof_name$Case_ = value == null ? $oneof_property_name$OneofCase.None : $oneof_property_name$OneofCase.$oneof_case_name$;\n"
     "  }\n"
     "}\n");
   if (SupportsPresenceApi(descriptor_)) {
@@ -236,7 +236,7 @@ void MessageOneofFieldGenerator::GenerateMembers(io::Printer* printer) {
     printer->Print(
       variables_,
       "$access_level$ bool Has$property_name$ {\n"
-      "  get { return $oneof_name$Case_ == $oneof_property_name$OneofCase.$property_name$; }\n"
+      "  get { return $oneof_name$Case_ == $oneof_property_name$OneofCase.$oneof_case_name$; }\n"
       "}\n");
     printer->Print(
       variables_,

src/google/protobuf/compiler/csharp/csharp_primitive_field.cc

@@ -296,7 +296,7 @@ void PrimitiveOneofFieldGenerator::GenerateMembers(io::Printer* printer) {
   }
   printer->Print(
     variables_,
-    "    $oneof_name$Case_ = $oneof_property_name$OneofCase.$property_name$;\n"
+    "    $oneof_name$Case_ = $oneof_property_name$OneofCase.$oneof_case_name$;\n"
     "  }\n"
     "}\n");
   if (SupportsPresenceApi(descriptor_)) {
@@ -307,7 +307,7 @@ void PrimitiveOneofFieldGenerator::GenerateMembers(io::Printer* printer) {
     printer->Print(
       variables_,
       "$access_level$ bool Has$property_name$ {\n"
-      "  get { return $oneof_name$Case_ == $oneof_property_name$OneofCase.$property_name$; }\n"
+      "  get { return $oneof_name$Case_ == $oneof_property_name$OneofCase.$oneof_case_name$; }\n"
       "}\n");
     printer->Print(
       variables_,

src/google/protobuf/compiler/csharp/csharp_wrapper_field.cc

@@ -233,7 +233,7 @@ void WrapperOneofFieldGenerator::GenerateMembers(io::Printer* printer) {
     "  get { return $has_property_check$ ? ($type_name$) $oneof_name$_ : ($type_name$) null; }\n"
     "  set {\n"
     "    $oneof_name$_ = value;\n"
-    "    $oneof_name$Case_ = value == null ? $oneof_property_name$OneofCase.None : $oneof_property_name$OneofCase.$property_name$;\n"
+    "    $oneof_name$Case_ = value == null ? $oneof_property_name$OneofCase.None : $oneof_property_name$OneofCase.$oneof_case_name$;\n"
     "  }\n"
     "}\n");
   if (SupportsPresenceApi(descriptor_)) {
@@ -244,7 +244,7 @@ void WrapperOneofFieldGenerator::GenerateMembers(io::Printer* printer) {
     printer->Print(
       variables_,
       "$access_level$ bool Has$property_name$ {\n"
-      "  get { return $oneof_name$Case_ == $oneof_property_name$OneofCase.$property_name$; }\n"
+      "  get { return $oneof_name$Case_ == $oneof_property_name$OneofCase.$oneof_case_name$; }\n"
       "}\n");
     printer->Print(
       variables_,