[WIP] Initialize parameters

[sloretz]

Work in progress towards initializing parameters.

Current state:

When the node is constructed yaml files passed as CLI args are parsed, and the parameters within are set on the node.

RCL

• need yaml parameter parser (YAML parameter parser rcl#235)
• need rcl function to get yaml file name from command line arguments (Support passing yaml parameter files via commandline  rcl#253)

Questions/Assumptions

• Assuming rclcpp needs to call methods to parse yaml because rcl doing it would cause a circular dependency between it and rcl_yaml_parse_params
• Assuming rcl will have a method for getting a path to a yaml file from an rcl_arguments_t Has method for getting all yaml paths specified
• Does rcl_yaml_param_parser dependency need to be exported? Yes
• Should rcl_yaml_param_parser namespace + nodename include a leading slash? currently it does not
• What was the idea of ParameterInitializationMap for? Why not std::vector<ParameterVariant>?

TODO

Bare minimum:

• NodeParameters should start parameter services in its constructor (Autostart parameter services #478)
  • Need to pass full Node instance to NodeParameters to give to ParameterService
• NodeParameters needs to get yaml file from CLI arguments (Initialize params via yaml from command line #488)
  1. If rcl_arguments_t passed to node options is not zero initialized, then get yaml files from it
  2. if node options use_global_argumentsisTrue` then get yaml files from global arguments.

Desired:

• Split ParameterVariant into Parameter which has a ParameterValue (Split ParameterVariant into Parameter and ParameterValue #481)
• rclcpp method to convert rcl_params_t to std::vector<Parameter> (or std::map<string, ParameterValue> or std::map<string, Parameter> ? ) (Convert rcl_params_t to ParameterMap #485)
• Allow passing std::vector<Parameter> into NodeParameters constructor. (Pass initial parameter values to node constructor #486)
  • Needed to initialize a node with parameters generated by roslaunch after it merges multiple yaml files together.
• node::create_parameter(name, value)
  • Declares a parameter is known by a node
• std::vector<Parameter> node::unknown_initial_parameters()
  • Returns a list of parameters that are in the yaml file but not known to the node
  • To be called by a user after all parameters have been created
• void node::raise_if_unknown_initial_parameters()
  • Raises exception if there is an unknown initial parameter
  • To be called by a user after all parameters have been created

[sloretz]

I should have put this info into an issue instead of a PR. The content is covered by #488 and #475. Closing.