Param dump on slam node not working if stack_size_to_use is not specified

[MarcoMagriDev]

Required Info:

• Operating System:
  • Ubuntu 24.04
• Installation type:
  • Both
• ROS Version
  • ROS2 Jazzy
• Version or commit hash:
  • Tag 2.8.2
• Laser unit:
  • Simulated

Steps to reproduce issue

ros2 launch slam_toolbox online_async_launch.py slam_params_file:=./my_params.yaml 

where my_params.yaml does not contain a specific value for stack_size_to_use

ros2 param dump /slam_node

Expected behavior

The dump output should contain parameters

Actual behavior

/slam_toolbox:
  ros__parameters: {}

Additional information

After investigating, I suspect the issue is related to how parameters with unspecified values are handled. Specifically, in the code, here:

slam_toolbox/src/slam_toolbox_common.cpp

Line 52 in bf1da76

"stack_size_to_use", rclcpp::ParameterType::PARAMETER_INTEGER, descriptor);

It seems that the /slam_node/get_parameters service returns an empty list when requesting a parameter with an unspecified value.
I'm not sure if this is a ROS-level issue or specific to this package, but the issue might stem from the handling of the stack_size parameter.
The value for stack_size, defined here, will never be used unless you modify this line as follows:

this->declare_parameter(
-      "stack_size_to_use", rclcpp::ParameterType::PARAMETER_INTEGER, descriptor);
+      "stack_size_to_use", stack_size, descriptor);

This would ensure the stack_size value is used properly.

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If you’d like, I can submit a pull request to fix this. Let me know!