src/google/protobuf/feature_resolver.h

// Protocol Buffers - Google's data interchange format
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#ifndef GOOGLE_PROTOBUF_FEATURE_RESOLVER_H__
#define GOOGLE_PROTOBUF_FEATURE_RESOLVER_H__

#include <memory>
#include <string>
#include <utility>

#include "absl/container/flat_hash_set.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/string_view.h"
#include "google/protobuf/descriptor.h"
#include "google/protobuf/descriptor.pb.h"
#include "google/protobuf/dynamic_message.h"

// Must be included last.
#include "google/protobuf/port_def.inc"

namespace google {
namespace protobuf {

// These helpers implement the unique behaviors of edition features.  For more
// details, see go/protobuf-editions-features.
class PROTOBUF_EXPORT FeatureResolver {
 public:
  FeatureResolver(FeatureResolver&&) = default;
  FeatureResolver& operator=(FeatureResolver&&) = delete;

  // Creates a new FeatureResolver at a specific edition.  This validates the
  // built-in features for the given edition, and calculates the default feature
  // set.
  static absl::StatusOr<FeatureResolver> Create(
      absl::string_view edition, const Descriptor* descriptor,
      const DescriptorPool* generated_pool =
          DescriptorPool::internal_generated_pool());

  // Registers a potential extension of the FeatureSet proto.  Any visible
  // extensions will be used during merging.  Returns an error if the extension
  // is a feature extension but fails validation.
  absl::Status RegisterExtensions(const FileDescriptor& file);

  // Creates a new feature set using inheritance and default behavior. This is
  // designed to be called recursively, and the parent feature set is expected
  // to be a fully merged one.
  // The returned FeatureSet will be fully resolved for any extensions that were
  // explicitly registered (in the custom pool) or linked into this binary (in
  // the generated pool).
  absl::StatusOr<FeatureSet> MergeFeatures(
      const FeatureSet& merged_parent, const FeatureSet& unmerged_child) const;

 private:
  FeatureResolver(absl::string_view edition, const Descriptor& descriptor,
                  std::unique_ptr<DynamicMessageFactory> message_factory,
                  std::unique_ptr<Message> defaults,
                  FeatureSet generated_defaults)
      : edition_(edition),
        descriptor_(descriptor),
        message_factory_(std::move(message_factory)),
        defaults_(std::move(defaults)),
        generated_defaults_(std::move(generated_defaults)) {}

  absl::Status RegisterExtensions(const Descriptor& message);
  absl::Status RegisterExtension(const FieldDescriptor& extension);

  std::string edition_;
  const Descriptor& descriptor_;
  absl::flat_hash_set<const FieldDescriptor*> extensions_;
  std::unique_ptr<DynamicMessageFactory> message_factory_;
  std::unique_ptr<Message> defaults_;
  FeatureSet generated_defaults_;
};

}  // namespace protobuf
}  // namespace google

#endif  // GOOGLE_PROTOBUF_FEATURE_RESOLVER_H__

#include "google/protobuf/port_undef.inc"