[Ruby] unable to read custom options from descriptor

[cocoahero]

It appears that #1198 has been closed as fixed. However, I am unable to figure out how to actually access any custom options on a message's descriptor. Calling to_h on the MessageOptions object returns {}, but to_json returns a promising value.

Below are some things I have tried, but have not found an access pattern that works.

Example

sandbox.proto

syntax = "proto3";

import "google/protobuf/descriptor.proto";

extend google.protobuf.MessageOptions {
  string my_custom_option = 50001;
}

message MyMessage {
  option (my_custom_option) = "hello";
}

sandbox_pb.rb (generated using protoc -I . --ruby_out=. sandbox.proto)

# frozen_string_literal: true
# Generated by the protocol buffer compiler.  DO NOT EDIT!
# source: sandbox.proto

require 'google/protobuf'

require 'google/protobuf/descriptor_pb'


descriptor_data = "\n\rsandbox.proto\x1a google/protobuf/descriptor.proto\"\x16\n\tMyMessage:\t\x8a\xb5\x18\x05hello:;\n\x10my_custom_option\x12\x1f.google.protobuf.MessageOptions\x18\xd1\x86\x03 \x01(\tb\x06proto3"

pool = Google::Protobuf::DescriptorPool.generated_pool
pool.add_serialized_file(descriptor_data)

MyMessage = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("MyMessage").msgclass

require_relative "sandbox_pb" 
# => true

MyMessage.descriptor.options 
# => <Google::Protobuf::MessageOptions: uninterpreted_option: []>

MyMessage.descriptor.options.to_h
# => {}

MyMessage.descriptor.options.to_json
# => "{\"[my_custom_option]\":\"hello\"}"

MyMessage.descriptor.options["my_custom_option"]
# => nil

MyMessage.descriptor.options["[my_custom_option]"]
# => nil

MyMessage.descriptor.options["(my_custom_option)"]
# => nil

MyMessage.descriptor.options.my_custom_option
# `method_missing': undefined method `my_custom_option' for an instance of Google::Protobuf::MessageOptions (NoMethodError)

Versions:

> ruby --version
ruby 3.3.1 (2024-04-23 revision c56cd86388) [arm64-darwin23]

> bundle show google-protobuf
~/.gem/ruby/3.3.1/gems/google-protobuf-4.26.1-arm64-darwin

> protoc --version
libprotoc 26.1

[haberman]

Here is the pattern you are looking for:

my_custom_option = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("my_custom_option")
my_custom_option.get(MyMessage.descriptor.options)

You can see an example in the tests:

protobuf/ruby/tests/basic.rb

Lines 684 to 698 in ee96b56

	assert_instance_of Google::Protobuf::OneofOptions, oneof_descriptor.options
	test_top_level_option = Google::Protobuf::DescriptorPool.generated_pool.lookup 'basic_test.test_top_level_option'
	assert_instance_of Google::Protobuf::FieldDescriptor, test_top_level_option
	assert_equal "Custom option value", test_top_level_option.get(oneof_descriptor.options)
	end
	def test_nested_extension
	descriptor = TestDeprecatedMessage.descriptor
	oneof_descriptor = descriptor.lookup_oneof("test_deprecated_message_oneof")
	assert_instance_of Google::Protobuf::OneofOptions, oneof_descriptor.options
	test_nested_option = Google::Protobuf::DescriptorPool.generated_pool.lookup 'basic_test.TestDeprecatedMessage.test_nested_option'
	assert_instance_of Google::Protobuf::FieldDescriptor, test_nested_option
	assert_equal "Another custom option value", test_nested_option.get(oneof_descriptor.options)
	end