C# Proto2 feature : Field presence and default values (#4642)

* Compiler changes

* Generated code changes

* Library changes

* Compiler style changes

* Generated style changes

* Fix Windows build errors

* Implement changes from review

* Reintroduce proto2 check

* Compiler changes (required handling review)

* Generated code changes (required handling review)

* Library changes (required handling review

* Field presence rewrite (compiler changes)

* Field presence rewrite (generated code changes)

* Compiler comment

* IFieldAccessor.HasValue library implementation

* Remove Clear methods and default values from proto3 code (Compiler)

* Remove Clear methods and default values from proto3 code (Generated)

* Remove Clear methods and default values from proto3 code (Library)

* Fix distcheck error

* Rewrite default string values to use base64 and convert

* Library changes (IMessage2)

* Compiler changes (IMessage2)

* Generated changes (IMessage2)

* Rebased and regenerated

* Compiler changes (initialized extension)

* Generated changes (initialized extension)

* Library changes (initialized extension)

* Refactor MessageExtensions.IsRequired

* Move string default value creator and bytes default value creator back to seperate methods

* Dead code cleanup

* Fixed segmentation fault
Removed unused header method declarations

1 files changed, 7 insertions, 1 deletions

diff --git a/src/google/protobuf/compiler/csharp/csharp_helpers.h b/src/google/protobuf/compiler/csharp/csharp_helpers.h
index ec0b1c77..5b9f90e0 100644
--- a/src/google/protobuf/compiler/csharp/csharp_helpers.h
+++ b/src/google/protobuf/compiler/csharp/csharp_helpers.h
@@ -107,9 +107,11 @@ std::string StringToBase64(const std::string& input);
 std::string FileDescriptorToBase64(const FileDescriptor* descriptor);
 
 FieldGeneratorBase* CreateFieldGenerator(const FieldDescriptor* descriptor,
-                                         int fieldOrdinal,
+                                         int presenceIndex,
                                          const Options* options);
 
+bool IsNullable(const FieldDescriptor* descriptor);
+
 // Determines whether the given message is a map entry message,
 // i.e. one implicitly created by protoc due to a map<key, value> field.
 inline bool IsMapEntryMessage(const Descriptor* descriptor) {
@@ -144,6 +146,10 @@ inline bool IsWrapperType(const FieldDescriptor* descriptor) {
       descriptor->message_type()->file()->name() == "google/protobuf/wrappers.proto";
 }
 
+inline bool IsProto2(const FileDescriptor* descriptor) {
+  return descriptor->syntax() == FileDescriptor::SYNTAX_PROTO2;
+}
+
 }  // namespace csharp
 }  // namespace compiler
 }  // namespace protobuf