Can't load non-absolute node name in parameter file

[Karsten1987]

Bug report

I have a parameter file in the style of

some_node_name:
  ros__parameters:
    a_list:
        - item1
        - item2

Expected behavior

ros2 param load works to load the correct parameters for node some_node_name even though the node name is not specified as absolute.

Actual behavior

error is raised: param file does not contain parameters for /some_node_name, only for nodes: dict_keys(['some_node_name'])

Note that there's a simple mismatch between the node names given that one is absolute.

Additional information

The reproducer here is based on a ros2-control example in which I would like to use the spawner script to spawn a controller with a given type and a parameter file.
@v-lopez fyi

[v-lopez]

I believe this is done on purpose, as the initial behavior allowed both, but after some discussion #590 (comment) and subsequent messages this was the conclusion: #600

[Karsten1987]

Isn't there a mismatch in the way we load parameters then? I can pass the same yaml file to a node within a launch file without the leading slash, but if I later on start a node and load that parameter file via ros2 param load ... the forward slash has to be present?

[v-lopez]

I don't know enough about all the use cases, but yeah sounds like a mismatch, which gives more importance to what I requested here ros2/rclpy#671 since basically the same code is reimplemented in multiple places, mismatches like this are bound to happen.

[v-lopez]

pinging @audrow @ivanpauno @clalancette

[ivanpauno]

Isn't there a mismatch in the way we load parameters then?

Maybe, I really don't know why rcl accepts a relative name in a parameters file.
Does that only match /some_node_name or also /my_ns/some_node_name?

I think we can copy what rcl does in ros2 param load.
In the case it only matches /some_node_name, we could use in the future /**/some_node_name to match both options.

[fujitatomoya]

Does that only match /some_node_name or also /my_ns/some_node_name?

both match.

i guess ros2 param load is the correct behavior. or rcl_yaml_param_parser?

[fujitatomoya]

This has been fixed with ros2/rclpy@3053a8a

• non-absolute node name case.

### ros2 param load
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 run demo_nodes_cpp parameter_blackboard
[INFO] [1698706220.128919541] [parameter_blackboard]: Parameter blackboard node named '/parameter_blackboard' ready, and serving '6' parameters already!
...
root@tomoyafujita:~/ros2_ws/colcon_ws# cat params.yaml
parameter_blackboard:
  ros__parameters:
    foo: bar
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param load /parameter_blackboard params.yaml
Set parameter foo successful
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param get /parameter_blackboard foo
String value is: bar

### --ros-args --params-file params.yaml
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 run demo_nodes_cpp parameter_blackboard --ros-args --params-file params.yaml
[INFO] [1698706337.110460136] [parameter_blackboard]: Parameter blackboard node named '/parameter_blackboard' ready, and serving '7' parameters already!
...
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param get /parameter_blackboard foo
String value is: bar

• absolute name case

### ros2 param load
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 run demo_nodes_cpp parameter_blackboard
[INFO] [1698706519.744738775] [parameter_blackboard]: Parameter blackboard node named '/parameter_blackboard' ready, and serving '6' parameters already!
...
root@tomoyafujita:~/ros2_ws/colcon_ws# cat params.yaml
/parameter_blackboard:
  ros__parameters:
    foo: bar
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param load /parameter_blackboard params.yaml
Set parameter foo successful
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param get /parameter_blackboard foo
String value is: bar

### --ros-args --params-file params.yaml
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 run demo_nodes_cpp parameter_blackboard --ros-args --params-file params.yaml
[INFO] [1698706478.171368734] [parameter_blackboard]: Parameter blackboard node named '/parameter_blackboard' ready, and serving '7' parameters already!
...
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param get /parameter_blackboard foo
String value is: bar

• wildcard case

### ros2 param load
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 run demo_nodes_cpp parameter_blackboard
[INFO] [1698706679.815384266] [parameter_blackboard]: Parameter blackboard node named '/parameter_blackboard' ready, and serving '6' parameters already!
...
root@tomoyafujita:~/ros2_ws/colcon_ws# cat params.yaml
/**/parameter_blackboard:
  ros__parameters:
    foo: bar
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param load /parameter_blackboard params.yaml
Set parameter foo successful
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param get /parameter_blackboard foo
String value is: bar

### --ros-args --params-file params.yaml
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 run demo_nodes_cpp parameter_blackboard --ros-args --params-file params.yaml
[INFO] [1698706712.118549727] [parameter_blackboard]: Parameter blackboard node named '/parameter_blackboard' ready, and serving '7' parameters already!
...
root@tomoyafujita:~/ros2_ws/colcon_ws# ros2 param get /parameter_blackboard foo
String value is: bar