"launch configuration 'True' does not exist"

[Maxme3ernard]

Hey,

I recently updated my simple_launch installation (from source) to use the add_action function.
However, without modifying my previously working launchfile, I now have an error.
My previous simple_launch version was quite old (1 or 2 years)

Some info:
ROS distro: foxy

$pip show launch
Name: launch
Version: 0.10.10
Summary: Launch processes specified in launch files.
Home-page: https://github.com/ros2/launch
Author: Dirk Thomas
Author-email: dthomas@osrfoundation.org
License: Apache License, Version 2.0
Location: /opt/ros/foxy/lib/python3.8/site-packages
Requires: setuptools
Required-by: launch-ros, topic-monitor

The error:

Task exception was never retrieved
future: <Task finished name='Task-2' coro=<LaunchService._process_one_event() done, defined at /opt/ros/foxy/lib/python3.8/site-packages/launch/launch_service.py:226> exception=SubstitutionFailure("launch configuration 'True' does not exist")>
Traceback (most recent call last):
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_service.py", line 228, in _process_one_event
    await self.__process_event(next_event)
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_service.py", line 248, in __process_event
    visit_all_entities_and_collect_futures(entity, self.__context))
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 45, in visit_all_entities_and_collect_futures
    futures_to_return += visit_all_entities_and_collect_futures(sub_entity, context)
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 45, in visit_all_entities_and_collect_futures
    futures_to_return += visit_all_entities_and_collect_futures(sub_entity, context)
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 45, in visit_all_entities_and_collect_futures
    futures_to_return += visit_all_entities_and_collect_futures(sub_entity, context)
  [Previous line repeated 3 more times]
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 38, in visit_all_entities_and_collect_futures
    sub_entities = entity.visit(context)
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/action.py", line 106, in visit
    if self.__condition is None or self.__condition.evaluate(context):
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/condition.py", line 44, in evaluate
    return self._predicate(context)
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/conditions/if_condition.py", line 43, in _predicate_func
    return evaluate_condition_expression(context, self.__predicate_expression)
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/conditions/evaluate_condition_expression_impl.py", line 41, in evaluate_condition_expression
    expanded_expression = perform_substitutions(context, expression)
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/utilities/perform_substitutions_impl.py", line 26, in perform_substitutions
    return ''.join([context.perform_substitution(sub) for sub in subs])
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/utilities/perform_substitutions_impl.py", line 26, in <listcomp>
    return ''.join([context.perform_substitution(sub) for sub in subs])
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/launch_context.py", line 232, in perform_substitution
    return substitution.perform(self)
  File "/opt/ros/foxy/lib/python3.8/site-packages/launch/substitutions/launch_configuration.py", line 98, in perform
    raise SubstitutionFailure(
launch.substitutions.substitution_failure.SubstitutionFailure: launch configuration 'True' does not exist

I fail to accurately trace this error further back, and the associated ~/.ros/log/logfile file is empty.
However, the error seems to occur when the line with sl.group(if_arg=sl.arg('arg_name')): is interpreted.

Thanks again for your work.

[oKermorgant]

Thanks for the feedback,

Can you give the launch file that leads to this error?
There might be several reasons why it occurs, including a launch argument that would contain "true", possibly wrongly changed to "True" under some conditions.