src/google/protobuf/cpp_features.proto

// Protocol Buffers - Google's data interchange format
// Copyright 2023 Google Inc.  All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd

syntax = "proto2";

package pb;

import "google/protobuf/descriptor.proto";

extend google.protobuf.FeatureSet {
  optional CppFeatures cpp = 1000;
}

message CppFeatures {
  // Whether or not to treat an enum field as closed.  This option is only
  // applicable to enum fields, and will be removed in the future.  It is
  // consistent with the legacy behavior of using proto3 enum types for proto2
  // fields.
  optional bool legacy_closed_enum = 1 [
    retention = RETENTION_RUNTIME,
    targets = TARGET_TYPE_FIELD,
    targets = TARGET_TYPE_FILE,
    edition_defaults = { edition: EDITION_PROTO2, value: "true" },
    edition_defaults = { edition: EDITION_PROTO3, value: "false" }
  ];
}