Features for ROS 2 Crystal

[dirk-thomas]

Features:

• Launch with life cycle
  • Details TBD
• Launch components into a "shared" process (see also https://github.com/ros2/launch/issues/160)
  • [rclcpp_components] CMake support macros for building Node's as "components"👷
    • [rclcpp] Consolidate node arguments into a single options class to simplify user defined Node classes 👷
      • [rclcpp] Consolidate how arguments are converted into configurations for the node (i.e. command line arguments into remappings and initial parameter values) 👷
  • [rclcpp_components] Node component container executable(s)👷
  • [launch_ros] Define nodes and then specify where they run separately
    • [launch] consider refactoring ExecuteProcess into Execute and Executable ([launch] consider refactoring ExecuteProcess into Execute and Executable #114)
• Nest launch files with namespacing
  • [launch] add new Action called IncludeLaunchDescription ([launch] add new Action called IncludeLaunchDescription #115) ✅
  • [launch] add new Action called GroupAction ([launch] add new Action called GroupAction #106) ✅
  • [launch] allow IncludeLaunchDescription to include other python launch files ([launch] allow IncludeLaunchDescription to include other python launch files #116) ✅
• Launch into/with Docker containers
  • Details TBD
• Pass params to nodes/components
  • [launch_ros] add ability to pass parameters to Node actions ([launch_ros] add ability to pass parameters to Node actions #117) ✅

Minor Features:

• [launch] add new concept for LaunchArgument ([launch] add new concept for LaunchArgument #107) ✅
• [launch] provide default console and filesystem logging for executed processes ([launch] provide default console and filesystem logging for executed processes #104) 👷
• [launch] add concept of Conditions ([launch] add concept of Conditions #105) ✅
• [launch] add new Action called UnsetLaunchConfiguration ([launch] add new Action called UnsetLaunchConfiguration #108) ✅
• [launch] add new Action called UnregisterEventHandler ([launch] add new Action called UnregisterEventHandler #110) ✅
• [launch] add option to RegisterEventHandler so that it unregisters itself after one event ([launch] add option to RegisterEventHandler so that it unregisters itself after one event #111) ✅

Technical Enhancements and Bugs:

• [launch] improve test coverage for non-core classes ([launch] improve test coverage for non-core classes #102) 👷
• [launch] prevent launch from hanging when unexpected exceptions occur internally ([launch] prevent launch from hanging when unexpected exceptions occur internally #112) 👷
• [launch] prevent Actions from being reused ([launch] prevent Actions from being reused #113)

Excluded Features:

• Distributed / remote launch
  • [launch] Multi-machine Launching ([launch] Multi-machine Launching #79)

Excluded Technical Enhancements and Bugs:

• [launch] refactor introspection system ([launch] refactor introspection system #103)
• [launch] check that iterable contains only types in ensure_argument_type() ([launch] check that iterable contains only types in ensure_argument_type() #109)

Anti-goals (things launch should not do itself):

• Capabilities
• QoS config from launch file

[wjwwood]

Closing because all sub tasks that were not completed for Crystal have their own issues.