bugs in load_parameter_file

[huweiATgithub]

Bug report

Required Info:

• Version or commit hash:
  

  ros2cli/ros2param/ros2param/api/__init__.py

  Lines 59 to 65 in 28d73d2

  	def get_parameter_value(*, string_value):
  	"""Guess the desired type of the parameter based on the string value."""
  	value = ParameterValue()
  	try:
  	yaml_value = yaml.safe_load(string_value)
  	except yaml.parser.ParserError:
  	yaml_value = string_value

Steps to reproduce issue

The current implementation has an extra yaml.safe_load for parameter value which has been loaded once already.
This will result in wrong results, e.g.,

key: ''

is once being loaded to {"key": ""}. Another load for the empty string "" will convert it into None.

Implementation considerations

Consider removing the extra yaml load.

[fujitatomoya]

@huweiATgithub can you provide the complete procedure (command line steps) that explain the problem here?

[huweiATgithub]

@huweiATgithub can you provide the complete procedure (command line steps) that explain the problem here?

1. having a node with a string type parameter
2. load parameter from a file using ros2 param load with file:

   /**:
     ros__parameters:
       param_name: ''

3. Notice an exception.

[fujitatomoya]

using fujitatomoya/ros2_test_prover@1fcc859 and the following procedure that you provided above, it does not generate the exception.

### start the node with string parameter
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 run prover_rclpy ros2cli_960 
[INFO] [1736797972.379024312] [minimal_param_node]: Got my_parameter: 
[INFO] [1736798063.849885193] [minimal_param_node]: Got my_parameter: 

### set the string parameter with ros2 param load
root@tomoyafujita:~/ros2_ws/colcon_ws# cat param_string_empty.yaml 
/**:
  ros__parameters:
    my_parameter: ''

root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param load minimal_param_node param_string_empty.yaml 
Set parameter my_parameter successful
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param get /minimal_param_node my_parameter
String value is: 
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param describe /minimal_param_node my_parameter
Parameter name: my_parameter
  Type: string
  Constraints:
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param load minimal_param_node param_string_empty.yaml 
Set parameter my_parameter successful
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param get /minimal_param_node my_parameter
String value is: 
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param describe /minimal_param_node my_parameter
Parameter name: my_parameter
  Type: string
  Constraints:

i would like to ask you again, could you please provide the Short, Self Contained, Correct (Compilable), Example?