Commits on Nov 2, 2023

1. 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 ros2#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 !

   

   haudren-woven committed Nov 2, 2023
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