Add a warning to action doc that it cannot be created under ament_python

[EmmanuelMess]

The https://docs.ros.org/en/jazzy/Tutorials/Intermediate/Creating-an-Action.html document should have a warning that only a C++ package can create an action. Messages and services have the same restriction AFAIK, but I haven't check if they say so. I think this is not readily apparent, and might lead to confusion as most of the docs are separated into "how to do in python" and "how to do in cpp", but actions have no such separation and only can be done in C++.

I dont know if there is an explicit recommendation to separate interfaces into their own packages, but it should probably be added to the action creation docs, if it makes sense.

[clalancette]

The https://docs.ros.org/en/jazzy/Tutorials/Intermediate/Creating-an-Action.html document should have a warning that only a C++ package can create an action. Messages and services have the same restriction AFAIK, but I haven't check if they say so.

To be clear, it is not that it has to be a C++ package, but rather that it has to be a CMake package; the language doesn't matter. And we do indeed say that it has to be a CMake package in https://docs.ros.org/en/rolling/Tutorials/Beginner-Client-Libraries/Custom-ROS2-Interfaces.html#create-a-new-package . So I'd be in favor of adding similar language to https://docs.ros.org/en/rolling/Tutorials/Intermediate/Creating-an-Action.html

[clalancette]

Oh, and in case it wasn't clear; we'd very much appreciate if you opened a PR adding it!

[EmmanuelMess]

To be clear, it is not that it has to be a C++ package, but rather that it has to be a CMake package; the language doesn't matter.

Wait, does that mean that you can create "crossed" cmake python packages? Is that documented somewhere I can read?

Oh, and in case it wasn't clear; we'd very much appreciate if you opened a PR adding it!

I am doing a graduate thesis right now, so that consumes most of my time, but if I can find the time I will fix these things.

[clalancette]

Wait, does that mean that you can create "crossed" cmake python packages? Is that documented somewhere I can read?

Yes, it is possible. The documentation for it is in https://docs.ros.org/en/rolling/How-To-Guides/Ament-CMake-Python-Documentation.html . That said, we don't really recommend using it much; it is better to use ament_cmake for C++ and for message/service/action packages, and ament_python for python packages.