Substitutions in parameter files

[ivanpauno]

Equivalent to the ROS 1 feature.
Fixes #96.

[hidmic]

Nice! Though I have to say I'm surprised that the substitution parser can handle multi-line strings.

[hidmic]

@ivanpauno nit: out of curiosity, why not:

with NamedTemporaryFile() as f:
    f.write(contents)
    yield f.name

instead?

[ivanpauno]

that won't unlink the file, just close it (unlink = remove from the filesystem).

[hidmic]

It will remove it if you don't set delete=False (which seems unnecessary in this case).

[ivanpauno]

ah yes, I guess that works

[ivanpauno]

Done in fc999d0.

[ivanpauno]

I now remember why I did this ...

Windows doesn't allow opening the same file twice.
If I yield from within the with statement, then I have a problem when opening the file in the test (see Windows CI results).

[hidmic]

Windows doesn't allow opening the same file twice.

That makes no sense.

[hidmic]

It appears you can reopen it, but not easily... (see here). Oh well, nevermind.

[hidmic]

LGTM pending green CI

[ivanpauno]

• Linux
• Linux-aarch64
• macOS
• Windows

[ivanpauno]

Windows again:

• Windows

[ivanpauno]

Last force push was because I forgot to sign the revert commit.

[hidmic]

LGTM!

[gramss]

Hey,

this looks really cool. Is there a simple user-faced example / documentation available for this?

I want to load a big param file and only replace certain parameter values (1-2 out of ~150). This is needed for CI testing.
Earlier this was done by a custom nav2 tool: https://github.com/ros-planning/navigation2/blob/main/nav2_common/nav2_common/launch/rewritten_yaml.py (But this seemed to stop working with foxy?)

Here is a example code using this: https://github.com/ros-planning/navigation2/blob/b8e9fba422d6e024767d1a5b668703625454fdcb/nav2_system_tests/src/system/test_system_launch.py#L45

Would be cool to maybe merge or replace the custom nav2 with official ros2_launch tools.

Thank you in advise!
Kind regards

[ivanpauno]

Hi @gramss, sorry for the delay but I didn't see your comment before.

I didn't write an example, but it would look something like this:

Node(
  executable=executable_name,
  package=package_name,
  parameters=[ParameterFile('path/to/file', allow_substs=True)]
)

The tests have an example parameter file, you can basically use the normal launch XML style substitutions in any position (see this guide for launch XML style substitutions, most of them are documented there).

Adding an example would actually be a great idea.
Feel free to add one in the paraterfile class docs or in the examples folder.

If you have any question feel free to ping me.

[andre-nguyen]

@ivanpauno Is there anything blocking us from backporting this to Foxy?

[ivanpauno]

@ivanpauno Is there anything blocking us from backporting this to Foxy?

By default, we backport only fixes and not features.
If there's enough interest to get this backported a patch doing that can be accepted, but that's up to the maintainers of the package @jacobperron @mjeronimo .

[jacobperron]

I tried cherry-picking this change to Foxy, but there are some conflicts. If someone wants to take the time to resolve them, I'm happy to review a PR.