// Copyright 2026 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package google.api;

import "google/protobuf/descriptor.proto";

option go_package = "google.golang.org/genproto/googleapis/api/annotations;annotations";
option java_multiple_files = true;
option java_outer_classname = "FieldBehaviorProto";
option java_package = "com.google.api";
option objc_class_prefix = "GAPI";

extend google.protobuf.FieldOptions {
  // A designation of a specific field behavior (required, output only, etc.)
  // in protobuf messages.
  //
  // Examples:
  //
  //   string name = 1 [(google.api.field_behavior) = REQUIRED];
  //   State state = 1 [(google.api.field_behavior) = OUTPUT_ONLY];
  //   google.protobuf.Duration ttl = 1
  //     [(google.api.field_behavior) = INPUT_ONLY];
  //   google.protobuf.Timestamp expire_time = 1
  //     [(google.api.field_behavior) = OUTPUT_ONLY,
  //      (google.api.field_behavior) = IMMUTABLE];
  repeated google.api.FieldBehavior field_behavior = 1052 [packed = false];
}

// An indicator of the behavior of a given field (for example, that a field
// is required in requests, or given as output but ignored as input).
// This **does not** change the behavior in protocol buffers itself; it only
// denotes the behavior and may affect how API tooling handles the field.
//
// Note: This enum **may** receive new values in the future.
enum FieldBehavior {
  // Conventional default for enums. Do not use this.
  FIELD_BEHAVIOR_UNSPECIFIED = 0;

  // Specifically denotes a field as optional.
  // While all fields in protocol buffers are optional, this may be specified
  // for emphasis if appropriate.
  OPTIONAL = 1;

  // Denotes a field as required.
  // This indicates that the field **must** be provided as part of the request,
  // and failure to do so will cause an error (usually `INVALID_ARGUMENT`).
  REQUIRED = 2;

  // Denotes a field as output only.
  // This indicates that the field is provided in responses, but including the
  // field in a request does nothing (the server *must* ignore it and
  // *must not* throw an error as a result of the field's presence).
  OUTPUT_ONLY = 3;

  // Denotes a field as input only.
  // This indicates that the field is provided in requests, and the
  // corresponding field is not included in output.
  INPUT_ONLY = 4;

  // Denotes a field as immutable.
  // This indicates that the field may be set once in a request to create a
  // resource, but may not be changed thereafter.
  IMMUTABLE = 5;

  // Denotes that a (repeated) field is an unordered list.
  // This indicates that the service may provide the elements of the list
  // in any arbitrary  order, rather than the order the user originally
  // provided. Additionally, the list's order may or may not be stable.
  UNORDERED_LIST = 6;

  // Denotes that this field returns a non-empty default value if not set.
  // This indicates that if the user provides the empty value in a request,
  // a non-empty value will be returned. The user will not be aware of what
  // non-empty value to expect.
  NON_EMPTY_DEFAULT = 7;

  // Denotes that the field in a resource (a message annotated with
  // google.api.resource) is used in the resource name to uniquely identify the
  // resource. For AIP-compliant APIs, this should only be applied to the
  // `name` field on the resource.
  //
  // This behavior should not be applied to references to other resources within
  // the message.
  //
  // The identifier field of resources often have different field behavior
  // depending on the request it is embedded in (e.g. for Create methods name
  // is optional and unused, while for Update methods it is required). Instead
  // of method-specific annotations, only `IDENTIFIER` is required.
  IDENTIFIER = 8;
}
