From b9ef0a388fa6fbb39e051679c15ec1608b184b68 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Herv=C3=A9=20Audren?= <herve.audren@woven-planet.global>
Date: Thu, 2 Nov 2023 15:15:37 +0900
Subject: [PATCH] Fixup environment leakage for Command

The `Command` substitution was not using the context's environment to
launch itself, and defaults to the parent process environment. This
caused bugs, as described in #715, which I re-state below.

Fixing this is very simple, just pass the environment of the context to
the subprocess spawned in Command.

How to reproduce? I couldn't quite come up with a very simple unit test
yet, but the below procedure should work.

First a simple executable:
```
import os

print(os.environ.get("FOO", "There is no foo"))
```

Place it somewhere on your path, I named it print_env.py.

Then the following launch file:
```
import launch

def generate_launch_description():
    ld = launch.LaunchDescription()

    ld.add_action(
        launch.actions.ExecuteProcess(
            cmd=["print_env.py"], additional_env={"FOO": "BAR"}, output="screen"
        )
    )

    ld.add_action(launch.actions.ExecuteProcess(cmd=["print_env.py"], output="screen"))

    ld.add_action(
        launch.actions.ExecuteProcess(
            cmd=["print_env.py"],
            output="screen",
            additional_env={
                "FOO": launch.substitutions.Command(
                    [
                        "print_env.py",
                    ]
                )
            },
        )
    )

    return ld
```
This launches three "printenv" processes:

* The first one has additional_env set to FOO=BAR
* The second one has nothing set
* The third one sets the FOO value to the contents of the environment variable,
  using a substitutions.Command

So I expect:

* BAR
* There is no foo
* There is no foo

What I get:

* BAR
* There is no foo
* BAR !
---
 launch/launch/substitutions/command.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/launch/launch/substitutions/command.py b/launch/launch/substitutions/command.py
index 0aed7a9d6..cd728877b 100644
--- a/launch/launch/substitutions/command.py
+++ b/launch/launch/substitutions/command.py
@@ -109,6 +109,7 @@ def perform(self, context: LaunchContext) -> Text:
         try:
             result = subprocess.run(
                 command,
+                env=context.environment,
                 stdout=subprocess.PIPE,
                 stderr=stderr,
                 universal_newlines=True)