Gnostic Support

protoc-gen-connect-openapi has support for the OpenAPI v3 annotations provided by the google/gnostic project. Here's an example of what this looks like in a protobuf file:

syntax = "proto3";

package example_with_gnostic;

import "gnostic/openapi/v3/annotations.proto";

option (gnostic.openapi.v3.document) = {
  info: {
    title: "Title from annotation";
    version: "Version from annotation";
    description: "Description from annotation";
    contact: {
      name: "Contact Name";
      url: "https://github.com/sudorandom/protoc-gen-connect-openapi";
      email: "hello@sudorandom.com";
    }
    license: {
      name: "MIT License";
      url: "https://github.com/sudorandom/protoc-gen-connect-openapi/blob/master/LICENSE";
    }
  }
  components: {
    security_schemes: {
      additional_properties: [
        {
          name: "BasicAuth";
          value: {
            security_scheme: {
              type: "http";
              scheme: "basic";
            }
          }
        }
      ]
    }
  }
};

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello(HelloRequest) returns (HelloReply) {
    option idempotency_level = NO_SIDE_EFFECTS;
    option (gnostic.openapi.v3.operation) = {
      deprecated: true,
      security: [
        {
          additional_properties: [
            {
              name: "BasicAuth";
              value: {
                value: []
              }
            }
          ]
        }
      ]
    };
  }
}

// The request message containing the user's name.
message HelloRequest {
  option (gnostic.openapi.v3.schema) = {title: "Custom title for a message"};

  string name = 1 [(gnostic.openapi.v3.property) = {title: "Custom title for a field"}];
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
}

File Options

Option	Supported?	Notes
(gnostic.openapi.v3.document).openapi	✅
(gnostic.openapi.v3.document).info	✅
(gnostic.openapi.v3.document).servers	✅
(gnostic.openapi.v3.document).paths	✅
(gnostic.openapi.v3.document).components	✅
(gnostic.openapi.v3.document).security	✅
(gnostic.openapi.v3.document).tags	✅
(gnostic.openapi.v3.document).external_docs	✅
(gnostic.openapi.v3.document).specification_extension	✅

Method Options

Option	Supported?
(gnostic.openapi.v3.schema).tags	✅
(gnostic.openapi.v3.schema).summary	✅
(gnostic.openapi.v3.schema).description	✅
(gnostic.openapi.v3.schema).external_docs	✅
(gnostic.openapi.v3.schema).operation_id	✅
(gnostic.openapi.v3.schema).parameters	✅
(gnostic.openapi.v3.schema).request_body	✅
(gnostic.openapi.v3.schema).responses	✅
(gnostic.openapi.v3.schema).callbacks	✅
(gnostic.openapi.v3.schema).deprecated	✅
(gnostic.openapi.v3.schema).security	✅
(gnostic.openapi.v3.schema).servers	✅
(gnostic.openapi.v3.schema).specification_extension	✅

Message Options

Option	Supported?
(gnostic.openapi.v3.schema).nullable	✅
(gnostic.openapi.v3.schema).discriminator	✅
(gnostic.openapi.v3.schema).read_only	✅
(gnostic.openapi.v3.schema).write_only	✅
(gnostic.openapi.v3.schema).xml	✅
(gnostic.openapi.v3.schema).external_docs	✅
(gnostic.openapi.v3.schema).example	✅
(gnostic.openapi.v3.schema).deprecated	✅
(gnostic.openapi.v3.schema).title	✅
(gnostic.openapi.v3.schema).multiple_of	✅
(gnostic.openapi.v3.schema).maximum	✅
(gnostic.openapi.v3.schema).exclusive_maximum	✅
(gnostic.openapi.v3.schema).minimum	✅
(gnostic.openapi.v3.schema).exclusive_minimum	✅
(gnostic.openapi.v3.schema).max_length	✅
(gnostic.openapi.v3.schema).min_length	✅
(gnostic.openapi.v3.schema).pattern	✅
(gnostic.openapi.v3.schema).max_items	✅
(gnostic.openapi.v3.schema).min_items	✅
(gnostic.openapi.v3.schema).unique_items	✅
(gnostic.openapi.v3.schema).max_properties	✅
(gnostic.openapi.v3.schema).min_properties	✅
(gnostic.openapi.v3.schema).string required	✅
(gnostic.openapi.v3.schema).Any	✅
(gnostic.openapi.v3.schema).type	✅
(gnostic.openapi.v3.schema).all_of	✅
(gnostic.openapi.v3.schema).one_of	✅
(gnostic.openapi.v3.schema).any_of	✅
(gnostic.openapi.v3.schema).not	✅
(gnostic.openapi.v3.schema).items	✅
(gnostic.openapi.v3.schema).properties	✅
(gnostic.openapi.v3.schema).additional_properties	✅
(gnostic.openapi.v3.schema).default	✅
(gnostic.openapi.v3.schema).description	✅
(gnostic.openapi.v3.schema).format	✅
(gnostic.openapi.v3.schema).specification_extension	✅

Field Options

Option	Supported?
(gnostic.openapi.v3.property).nullable	✅
(gnostic.openapi.v3.property).discriminator	✅
(gnostic.openapi.v3.property).read_only	✅
(gnostic.openapi.v3.property).write_only	✅
(gnostic.openapi.v3.property).xml	✅
(gnostic.openapi.v3.property).external_docs	✅
(gnostic.openapi.v3.property).example	✅
(gnostic.openapi.v3.property).deprecated	✅
(gnostic.openapi.v3.property).title	✅
(gnostic.openapi.v3.property).multiple_of	✅
(gnostic.openapi.v3.property).maximum	✅
(gnostic.openapi.v3.property).exclusive_maximum	✅
(gnostic.openapi.v3.property).minimum	✅
(gnostic.openapi.v3.property).exclusive_minimum	✅
(gnostic.openapi.v3.property).max_length	✅
(gnostic.openapi.v3.property).min_length	✅
(gnostic.openapi.v3.property).pattern	✅
(gnostic.openapi.v3.property).max_items	✅
(gnostic.openapi.v3.property).min_items	✅
(gnostic.openapi.v3.property).unique_items	✅
(gnostic.openapi.v3.property).max_properties	✅
(gnostic.openapi.v3.property).min_properties	✅
(gnostic.openapi.v3.property).string required	✅
(gnostic.openapi.v3.property).Any	✅
(gnostic.openapi.v3.property).type	✅
(gnostic.openapi.v3.property).all_of	✅
(gnostic.openapi.v3.property).one_of	✅
(gnostic.openapi.v3.property).any_of	✅
(gnostic.openapi.v3.property).not	✅
(gnostic.openapi.v3.property).items	✅
(gnostic.openapi.v3.property).properties	✅
(gnostic.openapi.v3.property).additional_properties	✅
(gnostic.openapi.v3.property).default	✅
(gnostic.openapi.v3.property).description	✅
(gnostic.openapi.v3.property).format	✅
(gnostic.openapi.v3.property).specification_extension	✅

For more information on how to use each option in your Protobuf file, you can reference the gnostic.openapi.v3 module documentation and the google/gnostic repo. Note that this is a new feature, so if find something that isn't supported that you need, please create an issue.