LaunchConfigurationNotEquals() always returns `True`

[hmellor]

Bug report

Required Info:

• Operating System:
  • Ubuntu 20.04
• Installation type:
  • Binaries
• Version or commit hash:
  • ros-foxy-launch: 0.10.5-1focal.20210423.000156
• DDS implementation:
  • (Don't know how to check but don't think it's relevant here?)
• Client library (if applicable):
  • launch

Steps to reproduce issue

I am trying to include an external launch file in a new launch file, but only if an argument in the new launch file is set. I have tried to do this using the condition kwarg where the specified condition evaluates to False if the value of arg is the default "". However, the condition always evaluates to True.

package_dir = ament_index_python.packages.get_package_share_directory("package")

declare_ncom = launch.actions.DeclareLaunchArgument("arg", default_value="")
arg = launch.substitutions.LaunchConfiguration("arg", default="")

launch_description = launch.launch_description_sources.PythonLaunchDescriptionSource(f"{package_dir}/launch/launch.py")
package_launch = launch.actions.IncludeLaunchDescription(
    condition=launch.conditions.LaunchConfigurationNotEquals(arg, ""), 
    launch_description_source=launch_description,
    launch_arguments={"arg": arg}.items(),
)

Expected behavior

If the arg has not been set, then package_launch's condition should evaluate to False and the launch.py should not run from the new launch file.

Actual behavior

launch.py always runs.

[hidmic]

@HMellor LaunchConfigurationNotEquals takes the launch configuration name, not the object itself.

Having said that, I'm open to supporting that OR improving documentation to make it clearer. Would you be willing to do the latter?

[hmellor]

Ah ok, the type hinting for the argument was SomeSubstitutionsType, which is non-specific and open to being misinterpreted (such as I have done here). If it's just the docstring I'd be happy to make a pull request to clarify the argument. Have I understood you correctly @hidmic?

[hidmic]

If it's just the docstring I'd be happy to make a pull request to clarify the argument. Have I understood you correctly @hidmic?

Yes, exactly.