Improve load times by skipping serialization of entities when unecessary.

examples/plugin/custom_sensor_system/CMakeLists.txt

@@ -20,7 +20,7 @@ include(FetchContent)
 FetchContent_Declare(
  sensors_clone
  GIT_REPOSITORY https:/gazebosim/gz-sensors
- GIT_TAG main
+ GIT_TAG gz-sensors${GZ_SENSORS_VER}
 )
 FetchContent_Populate(sensors_clone)
 add_subdirectory(${sensors_clone_SOURCE_DIR}/examples/custom_sensor ${sensors_clone_BINARY_DIR})

include/gz/sim/components/Model.hh

@@ -75,10 +75,18 @@
  }
  }
 
- _out << "<?xml version=\"1.0\" ?>"
- << "<sdf version='" << SDF_PROTOCOL_VERSION << "'>"
- << (skip ? std::string() : modelElem->ToString(""))
- << "</sdf>";
+ if (!skip)
+ {
+ _out << "<?xml version=\"1.0\" ?>"
+ << "<sdf version='" << SDF_PROTOCOL_VERSION << "'>"
+ << modelElem->ToString("")
+ << "</sdf>";
+
+ }
+ else
+ {
+ _out << "";
+ }
  return _out;
  }
 
@@ -89,13 +97,18 @@
  public: static std::istream &Deserialize(std::istream &_in,
  sdf::Model &_model)
  {
- sdf::Root root;
  std::string sdf(std::istreambuf_iterator<char>(_in), {});
+ if (sdf.empty())
+ {
+ return _in;
+ }
 
+ // Its super expensive to create an SDFElement for some reason
+ sdf::Root root;
  sdf::Errors errors = root.LoadSdfString(sdf);
  if (!root.Model())
  {
- gzwarn << "Unable to deserialize sdf::Model" << std::endl;
+ gzwarn << "Unable to deserialize sdf::Model " << sdf<< std::endl;
  return _in;
  }