src/google/protobuf/compiler/retention.cc

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
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#include "google/protobuf/compiler/retention.h"

#include <memory>
#include <string>
#include <vector>

#include "google/protobuf/descriptor.h"
#include "google/protobuf/dynamic_message.h"

namespace google {
namespace protobuf {
namespace compiler {

namespace {

// Recursively strips any options with source retention from the message.
void StripMessage(Message& m) {
  const Reflection* reflection = m.GetReflection();
  std::vector<const FieldDescriptor*> fields;
  reflection->ListFields(m, &fields);
  for (const FieldDescriptor* field : fields) {
    if (field->options().retention() == FieldOptions::RETENTION_SOURCE) {
      reflection->ClearField(&m, field);
    } else if (field->type() == FieldDescriptor::TYPE_MESSAGE) {
      if (field->is_repeated()) {
        int field_size = reflection->FieldSize(m, field);
        for (int i = 0; i < field_size; ++i) {
          StripMessage(*reflection->MutableRepeatedMessage(&m, field, i));
        }
      } else {
        StripMessage(*reflection->MutableMessage(&m, field));
      }
    }
  }
}

// Converts the descriptor to a dynamic message if necessary, and then strips
// out all source-retention options.
//
// The options message may have custom options set on it, and these would
// ordinarily appear as unknown fields since they are not linked into protoc.
// Using a dynamic message allows us to see these custom options. To convert
// back and forth between the generated type and the dynamic message, we have
// to serialize one and parse that into the other.
void ConvertToDynamicMessageAndStripOptions(Message& m,
                                            const DescriptorPool& pool) {
  // We need to look up the descriptor in the pool so that we can get a
  // descriptor which knows about any custom options that were used in the
  // .proto file.
  const Descriptor* descriptor = pool.FindMessageTypeByName(m.GetTypeName());

  if (descriptor == nullptr) {
    // If the pool does not contain the descriptor, then this proto file does
    // not transitively depend on descriptor.proto, in which case we know there
    // are no custom options to worry about.
    StripMessage(m);
  } else {
    DynamicMessageFactory factory;
    std::unique_ptr<Message> dynamic_message(
        factory.GetPrototype(descriptor)->New());
    std::string serialized;
    ABSL_CHECK(m.SerializeToString(&serialized));
    ABSL_CHECK(dynamic_message->ParseFromString(serialized));
    StripMessage(*dynamic_message);
    ABSL_CHECK(dynamic_message->SerializeToString(&serialized));
    ABSL_CHECK(m.ParseFromString(serialized));
  }
}

// Returns a const reference to the descriptor pool associated with the given
// descriptor.
template <typename DescriptorType>
const google::protobuf::DescriptorPool& GetPool(const DescriptorType& descriptor) {
  return *descriptor.file()->pool();
}

// Specialization for FileDescriptor.
const google::protobuf::DescriptorPool& GetPool(const FileDescriptor& descriptor) {
  return *descriptor.pool();
}

// Returns the options associated with the given descriptor, with all
// source-retention options stripped out.
template <typename DescriptorType>
auto StripLocalOptions(const DescriptorType& descriptor) {
  auto options = descriptor.options();
  ConvertToDynamicMessageAndStripOptions(options, GetPool(descriptor));
  return options;
}

}  // namespace

FileDescriptorProto StripSourceRetentionOptions(const FileDescriptor& file) {
  FileDescriptorProto file_proto;
  file.CopyTo(&file_proto);
  ConvertToDynamicMessageAndStripOptions(file_proto, *file.pool());
  return file_proto;
}

EnumOptions StripLocalSourceRetentionOptions(const EnumDescriptor& descriptor) {
  return StripLocalOptions(descriptor);
}

EnumValueOptions StripLocalSourceRetentionOptions(
    const EnumValueDescriptor& descriptor) {
  return StripLocalOptions(descriptor);
}

FieldOptions StripLocalSourceRetentionOptions(
    const FieldDescriptor& descriptor) {
  return StripLocalOptions(descriptor);
}

FileOptions StripLocalSourceRetentionOptions(const FileDescriptor& descriptor) {
  return StripLocalOptions(descriptor);
}

MessageOptions StripLocalSourceRetentionOptions(const Descriptor& descriptor) {
  return StripLocalOptions(descriptor);
}

MethodOptions StripLocalSourceRetentionOptions(
    const MethodDescriptor& descriptor) {
  return StripLocalOptions(descriptor);
}

OneofOptions StripLocalSourceRetentionOptions(
    const OneofDescriptor& descriptor) {
  return StripLocalOptions(descriptor);
}

ServiceOptions StripLocalSourceRetentionOptions(
    const ServiceDescriptor& descriptor) {
  return StripLocalOptions(descriptor);
}

}  // namespace compiler
}  // namespace protobuf
}  // namespace google