https://answers.ros.org/question/368144/colcon-build-fails-on-newly-created-package/?answer=396325#post-id-396325

I agree that a warning about the hyphen would be informative here!

For what it is worth, while using underscore is our best practice, I don't think hyphens should fail. I would prefer we figure out why hyphens are having problems.

For what it is worth, while using underscore is our best practice, I don't think hyphens should fail. I would prefer we figure out why hyphens are having problems.

I think what's happening is that when you invoke ros2 pkg create --build-type ament_python --license MIT --node-name hello-world hello-world-python-1, a module named hello-world is created. I don't know where exactly it fails, but from what I understand modules with hyphens in the name can't be loaded/imported.

This thread touches on something tangentially related: https://stackoverflow.com/a/54599368

I think what's happening is that when you invoke ros2 pkg create --build-type ament_python --license MIT --node-name hello-world hello-world-python-1, a module named hello-world is created. I don't know where exactly it fails, but from what I understand modules with hyphens in the name can't be loaded/imported.

Oh, I see! Thanks for the explanation. OK, in that case I do agree that blocking them completely at ros2 pkg create time makes sense (for ament_python packages, at least).

(as a side note, I do believe that we can have hyphenated C++ packages, so for now I wouldn't change that semantic)

Yes agree, C++ works, but for python that's a language limitation afaik.
This is also mentioned in Pep-8.

I'll then happily open a PR for that :)

For what it's worth, it seems the issue you may be facing is not from the package name, but the setupcfg file that get's autogenerated.

It seems when the command is run, the setup.cfg file is created like so:

[develop]
script-dir=$base/lib/hello-world-python
[install]
install-scripts=$base/lib/hello-world-python

When it should be :

[develop]
script_dir=$base/lib/hello-world-python
[install]
install_scripts=$base/lib/hello-world-python

Where the difference is a underscore vs the hyphen. (Should be script_dir vs the autogenerated script-dir)

I hope this is helpful and related to resolving your issue.