Location of included launch files cannot be determined

[dseredyn]

Bug report

• Operating System:
  • Ubuntu 22.04
• Installation type: binary
• Version or commit hash: humble, from distro
• DDS implementation:
• Client library (if applicable):

Steps to reproduce issue

I'm trying to make a tool for examination of launch file structure and to visualize a tree of included launch files (python).

The following code, where ent is IncludeLaunchDescription object, should output a path to the included launch file, but instead it returns a string that refers to Python object pointer, e.g.<launch.substitutions.path_join_substitution.PathJoinSubstitution object at 0x74b241481780>

if isinstance(ent, IncludeLaunchDescription):
  print(isinstance(ent.launch_description_source.location, str))
  print(ent.launch_description_source.location)

ACTUAL output:

True
<launch.substitutions.path_join_substitution.PathJoinSubstitution object at 0x74b241481780>

EXPECTED output:

True
/home/user/ws/share/...

This should be fixed to enable error reporting for individual launch files included from other launch files. Now it is impossible to automatically determine which launch file has defined a problematic action.

I'm using PAL robotics scripts to build launch files. The function that includes a launch file is:

def include_launch_py_description(
        pkg_name: SomeSubstitutionsType,
        paths: List[SomeSubstitutionsType],
        **kwargs) -> Action:

    pkg_dir = FindPackageShare(pkg_name)
    full_path = PathJoinSubstitution([pkg_dir] + paths)

    return IncludeLaunchDescription(
        PythonLaunchDescriptionSource(
            full_path),
        **kwargs)

Also, it looks like IncludeLaunchDescription convert Substitutions into a string <launch.substitutions.path_join_substitution.PathJoinSubstitution object at ...>:

def include_launch_py_description(
        pkg_name: SomeSubstitutionsType,
        paths: List[SomeSubstitutionsType],
        **kwargs) -> Action:

    pkg_dir = FindPackageShare(pkg_name)
    full_path = PathJoinSubstitution([pkg_dir] + paths)
    print(full_path)
    for sub in full_path.substitutions:
        print(sub.describe())

    incl = IncludeLaunchDescription(
        PythonLaunchDescriptionSource(
            full_path),
        **kwargs)

    print(isinstance(incl.launch_description_source.location, str))
    print(incl.launch_description_source.location)
    return incl

The output:

<launch.substitutions.path_join_substitution.PathJoinSubstitution object at 0x76505beb75e0>
FindPackageShare(pkg='tiago_description')
'launch'
'robot_state_publisher.launch.py'
True
<launch.substitutions.path_join_substitution.PathJoinSubstitution object at 0x76505beb75e0>

[fujitatomoya]

@wjwwood can you take a look about this?