LuaForConfiguration

#format rst

Overview

Right now in Goby2 we're using Protocol Buffers Text Format syntax for configuration files, which is nice because you have to define a strict schema (the .proto file) for your configuration in the same (default) language used on the wire.

E.g.,

[[attachments/simple.proto)simple.proto`attachment:None%60_ (defines a "message" that gets compiled to a C++ / Java / Python class]]

message SimpleConfig
{
    required double a_double = 1;
    optional bool a_bool = 2;
    optional string a_string = 3;
}

[[attachments/simple.pb.cfg)simple.pb.cfg`attachment:None%60_ (equivalent to a single ProcessConfig block of a ".moos" file]]

a_double: 3.14159
a_bool: true
a_string: "hello"

Which becomes (in C++) simple.cpp`attachment:None%60_

#include "simple.pb.h"
#include "goby/core.h"
SimpleConfig my_cfg; // instantiate a C++ class version of the SimpleConfig protobuf message
class Simple : public goby::core::Application
{
   Simple() : goby::core::Application(&my_cfg) // Application reads the "simple.pb.cfg" and populates "my_cfg" if valid
   {
      assert(my_cfg.a_double() == 3.14159);
      assert(my_cfg.a_bool() == true);
      assert(my_cfg.a_string() == "hello");
      std::cout << my_cfg.DebugString() << std::endl;
      exit(0);
   }
   void loop()
   {}
};
int main(int argc, char* argv[])
{
   return goby::run<Simple>(argc, argv);
}

which you can run by

protoc --cpp_out . simple.proto
g++ simple.cpp simple.pb.cc -o simple -lgoby_core -I ~/goby/2.0/include -L ~/goby/2.0/lib
./simple simple.pb.cfg -d

The problem is however, that [[attachments/simple.pb.cfg_simple.pb.cfg`attachment:None%60_ is static and contains no scripting capability. What would be powerful is combining the schema (.proto) enforced configuration that we already have with the scripting power provided by Lua. I think this could work perhaps by redefining (or as an option) attachment:simple.pb.cfg]]simple.pb.cfg`attachment:None%60_ to simple.lua:

simple.lua

SimpleConfig =
{
  a_double  = math.pi,
  a_bool    = true,
  a_string  = "hello",
}

With some additional code in goby::core::Application to call the Lua API and instantiate the appropriate proto file, the simple.cpp`attachment:None%60_ code shouldn't need to change.

Support for class based configuration hierarchy