Update parameters typing to leverage recursive types

[christophebedard]

Looks like recursive types are supported by mypy now: python/mypy#731.

1. There's a TODO here:

   launch_ros/launch_ros/launch_ros/parameters_type.py

   Lines 55 to 57 in 3569f0d

   	# TODO(sloretz) Recursive type when mypy supports them python/mypy#731
   	_SomeParametersDict = Mapping[SomeParameterName, Any]
   	SomeParametersDict = Mapping[SomeParameterName, Union[SomeParameterValue, _SomeParametersDict]]

   • Update the code to leverage recursive types and remove the TODO.
2. There's also a comment below that mentions "(flattened to avoid having a recursive type)," which could therefore probably also be updated, although I'm not quite sure what to do there:

   launch_ros/launch_ros/launch_ros/parameters_type.py

   Lines 72 to 73 in 3569f0d

   	# Normalized (flattened to avoid having a recursive type) parameter dict
   	ParametersDict = Dict[ParameterName, ParameterValue]

   • I'm not exactly sure what it refers to. However, for this one, we could probably remove "(flattened to avoid having a recursive type)" from the comment and leave the code as-is.
3. Finally, there are a few references to "making/appeasing mypy" in launch_ros/utilities/normalize_parameters.py. Perhaps that could be revisited to see if we can simplify it. # type: comments could also be updated to the more modern type annotations.

[InvincibleRMC]

rhel mypy's version is 0.971. So Using the recursive types would fail since version >= 1.7 is needed.

[christophebedard]

Good point! But I believe it's using 0.971.

• On RHEL 9 (target for Jazzy and Rolling), we install python3-mypy, which seems to be version 0.971: https://pkgs.org/search/?q=python3-mypy. See docs: https://docs.ros.org/en/rolling/Installation/RHEL-Install-RPMs.html#install-development-tools-optional. See also ROS 2 CI: https://github.com/ros2/ci/blob/022da8a9eaa83b4ae8f7b770bdd2a4c700bf1d70/linux_docker_resources/Dockerfile-RHEL#L141
• On RHEL 8 (target for Humble), we install mypy from pip. In the docs, we install version 0.931 specifically: https://docs.ros.org/en/humble/Installation/Alternatives/RHEL-Development-Setup.html#install-development-tools-and-ros-tools. In ROS 2 CI, we install version 0.942: https://github.com/ros2/ci/blob/022da8a9eaa83b4ae8f7b770bdd2a4c700bf1d70/linux_docker_resources/Dockerfile-RHEL#L202-L207.

I guess we'll have to wait a little while more then, since I don't think we'll switch to using pip to install a newer mypy version. I'll just leave this open for now.

[alsora]

Hi @christophebedard, we discussed this issue in the waffle meeting and we decided to re-add "help wanted" label.
Do you have any thoughts on that?

[christophebedard]

I removed it because this issue wasn't immediately actionable based on my quick investigation, but, sure, that works for me!