Accessing custom options in python protoc

Question

metadata3.proto

syntax = "proto3";

import "google/protobuf/descriptor.proto";

package metas3;

message MessageOptionsMetadata3 {
  optional string message_options_field1 = 1;
  optional string message_options_field2 = 2;
  optional string message_options_field3 = 3;
}

extend google.protobuf.MessageOptions {
  MessageOptionsMetadata3 message_options_metadata3 = 50000;
}

message FileOptionsMetadata3 {
  optional string file_options_field1 = 1;
  optional string file_options_field2 = 2;
  optional string file_options_field3 = 3;
  optional string file_options_field4 = 4;
}

extend google.protobuf.FileOptions {
  FileOptionsMetadata3 file_options_metadata3 = 60000;
}

extend google.protobuf.FieldOptions {
  repeated string event_type = 70000;
}

my_proto_file.proto

syntax = "proto3";

import "metadata3.proto";
import "google/protobuf/descriptor.proto";

package events;

extend google.protobuf.MessageOptions {
  optional string my_option = 51234;
}

message MyMessage {
  option (my_option) = "Hello world!";
  option (metas3.message_options_metadata3).message_options_field1 = "Message option";
}

Generated metadata3_pb2.py and used that in protoc plugin as follows,

protoc -I=./protos --python_out=./protos_generated --plugin=./protos_generated/metadata3_pb2.py ./protos/*.proto

my_proto_file_pb2.py

# -*- coding: utf-8 -*-
# Generated by the protocol buffer compiler.  DO NOT EDIT!
# source: my_proto_file.proto
"""Generated protocol buffer code."""
from google.protobuf import descriptor as _descriptor
from google.protobuf import message as _message
from google.protobuf import reflection as _reflection
from google.protobuf import symbol_database as _symbol_database
# @@protoc_insertion_point(imports)

_sym_db = _symbol_database.Default()


import metadata3_pb2 as metadata3__pb2
from google.protobuf import descriptor_pb2 as google_dot_protobuf_dot_descriptor__pb2


DESCRIPTOR = _descriptor.FileDescriptor(
  name='my_proto_file.proto',
  package='events',
  syntax='proto3',
  serialized_options=None,
  create_key=_descriptor._internal_create_key,
  serialized_pb=b'\n\x13my_proto_file.proto\x12\x06\x65vents\x1a\x0fmetadata3.proto\x1a google/protobuf/descriptor.proto\"1\n\tMyMessage:$\x92\x82\x19\x0cHello world!\x82\xb5\x18\x10\n\x0eMessage option:7\n\tmy_option\x12\x1f.google.protobuf.MessageOptions\x18\xa2\x90\x03 \x01(\t\x88\x01\x01\x62\x06proto3'
  ,
  dependencies=[metadata3__pb2.DESCRIPTOR,google_dot_protobuf_dot_descriptor__pb2.DESCRIPTOR,])


MY_OPTION_FIELD_NUMBER = 51234
my_option = _descriptor.FieldDescriptor(
  name='my_option', full_name='events.my_option', index=0,
  number=51234, type=9, cpp_type=9, label=1,
  has_default_value=False, default_value=b"".decode('utf-8'),
  message_type=None, enum_type=None, containing_type=None,
  is_extension=True, extension_scope=None,
  serialized_options=None, file=DESCRIPTOR,  create_key=_descriptor._internal_create_key)


_MYMESSAGE = _descriptor.Descriptor(
  name='MyMessage',
  full_name='events.MyMessage',
  filename=None,
  file=DESCRIPTOR,
  containing_type=None,
  create_key=_descriptor._internal_create_key,
  fields=[
  ],
  extensions=[
  ],
  nested_types=[],
  enum_types=[
  ],
  serialized_options=b'\222\202\031\014Hello world!\202\265\030\020\n\016Message option',
  is_extendable=False,
  syntax='proto3',
  extension_ranges=[],
  oneofs=[
  ],
  serialized_start=82,
  serialized_end=131,
)

DESCRIPTOR.message_types_by_name['MyMessage'] = _MYMESSAGE
DESCRIPTOR.extensions_by_name['my_option'] = my_option
_sym_db.RegisterFileDescriptor(DESCRIPTOR)

MyMessage = _reflection.GeneratedProtocolMessageType('MyMessage', (_message.Message,), {
  'DESCRIPTOR' : _MYMESSAGE,
  '__module__' : 'my_proto_file_pb2'
  # @@protoc_insertion_point(class_scope:events.MyMessage)
  })
_sym_db.RegisterMessage(MyMessage)

google_dot_protobuf_dot_descriptor__pb2.MessageOptions.RegisterExtension(my_option)

_MYMESSAGE._options = None
# @@protoc_insertion_point(module_scope)

Accessing options defined in the file works as the option in set in generated code

value = my_proto_file_pb2.MyMessage.DESCRIPTOR.GetOptions().Extensions[my_proto_file_pb2.my_option]

But options imported from external proto files doesn't seem to be set and hence isn't accessible

value = my_proto_file_pb2.MyMessage.DESCRIPTOR.GetOptions().Extensions[my_proto_file_pb2.message_options_field1]

Answer 1

--plugin=./protos_generated/metadata3_pb2.py

This looks weird to me. What do you expect it should do?

serialized_options=b'\222\202\031\014Hello world!\202\265\030\020\n\016Message option',

It looks like your Message option is included also. So the problem is only in accessing it.

value = my_proto_file_pb2.MyMessage.DESCRIPTOR.GetOptions()
           .Extensions[my_proto_file_pb2.message_options_field1]

As far as I can tell there is no my_proto_file_pb2.message_options_field1 defined in my_proto_file.proto. Instead it should be metadata3_pb2.message_options_metadata3.