Multiple SetEnvrionmentVariable override each other when launching multiple nodes

[fas2037]

Bug report

Required Info:

• Operating System:
  • Ubuntu 20.04
• Installation type:
  • Binaries
• Version:
  • Galactic
• DDS implementation:
  • Cyclone DDS

Steps to reproduce issue

Generate multiple nodes and call SetEnvironmentVariable in the LaunchDescription:

from launch import LaunchDescription
from launch_ros.actions import Node
from launch.actions import SetEnvironmentVariable


def generate_launch_description():
    return LaunchDescription([
        SetEnvironmentVariable(name='TEST', value='0'),
        Node(
            package="test_0",
            executable="test_0",
            name="test_0_node",
            output="screen",
        )
    ])

from launch import LaunchDescription
from launch_ros.actions import Node
from launch.actions import SetEnvironmentVariable


def generate_launch_description():
    return LaunchDescription([
        SetEnvironmentVariable(name='TEST', value='1),
        Node(
            package="test_1",
            executable="test_1",
            name="test_1_node",
            output="screen",
        )
    ])

Launch both nodes:

from ament_index_python.packages import get_package_share_directory

def generate_launch_description():

    nodes = ["test_0", "test_1"]
    includes = []

    for n in nodes:
        includes.append(launch.actions.IncludeLaunchDescription(launch.launch_description_sources.PythonLaunchDescriptionSource(get_package_share_directory(n) + '/launch/' + n + '_launch.py')))

    return launch.LaunchDescription(includes)

Expected behavior

When accessing the environmental variable in node 'test_0' it should have the value '0'.
When accessing the environmental variable in node 'test_1' it should have the value '1'.

Actual behavior

When accessing the environmental variable in node 'test_0' it has the value '1'.
When accessing the environmental variable in node 'test_1' it has the value '1'.

Additional information

---

[hidmic]

@fas2037 SetEnvironmentVariable mutates the environment of launch itself (which is one, later propagated to its children). Even if that wasn't the case, it still wouldn't do what you expect since LaunchDescription instances do not execute anything and there's no lexical scoping to rely on.

For your specific use case, I'd suggest using the append_env argument of the Node class. If you'd like to see scoping improved, there have been some discussions in #501 and #313.

[jacobperron]

I think #601 resolves this ticket. @fas2037 correct me if I'm wrong.

edit: Or at least it should be possible to do what you want using GroupAction with the includes.