syntax = "proto3"; import public "other.proto"; option java_package = "com.example.foo"; enum EnumAllowingAlias { option allow_alias = true; ALLOWING_UNSPECIFIED = 0; STARTED = 1; RUNNING = 2 [(custom_option) = "hello world"]; } message Outer { option (my_option).a = true; message Inner { // Level 2 int64 ival = 1; } inner inner_message = 2; EnumAllowingAlias enum_field =3; map my_map = 4; }