[ros-users] [Discourse.ros.org] [Next Generation ROS] Questioning the .launch.py file extension

[William Woodall]

I was trying to approximate the `.launch` extension that we had in ROS 1 (which would have contained XML). When people wanted to compose a launch file out of XML files they would use `.xml` for the parts, indicating that the `.launch` files were actually viable entry points for launching.

The `.launch.py` was a way to imply it was both an entry point and clue editors to the markup of the contents. It is currently completely optional and is only considered with tab-completion.

I had imagined that people who wanted to unit test their python code used in launch files would place testable code in `.py` files and have a single `.launch.py` that uses the code in the `.py` files to return the launch description. I have also imagined that if you wanted to do an integration test where you actually instantiate the launch file for introspection or launching you'd do that with the `launch` API (which handles imports for you).

For general purpose composition (a launch file including another launch file) that can (and probably should be) done with the `IncludeLaunchDescription` action in launch.

To alleviate other use cases we could expose the `importlib` logic used in launch itself to handle the `.launch.py` suffix.

That all being said, while I prefer the aesthetics of `.launch.py`, I would be fine with canonicalizing `_launch.py` or something else and I'm interested in hearing from others on the topic.





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