Support passing additional search paths via package_dirs argument

[flferretti]

This pull request adds support for custom environment variables as additional search paths when resolving a robotics URI. The resolve_robotics_uri function now accepts an optional extra_path parameter, which allows users to specify the name of an environment variable associated with a search path. If extra_path is provided, the function will include the path associated with the environment variable to the search paths.

Example usage to find meshes path:

import os
import pathlib

import robot_descriptions.ur10_description
from robot_descriptions._package_dirs import get_package_dirs

from resolve_robotics_uri_py import resolve_robotics_uri

model_urdf_path = pathlib.Path(robot_descriptions.ur10_description.URDF_PATH)

package_dirs = get_package_dirs(robot_descriptions.ur10_description)
mesh_path = resolve_robotics_uri(
    uri="package://example-robot-data/robots/ur_description/meshes/ur10/collision/shoulder.stl",
    package_dirs=package_dirs,
)

print(f"Mesh path: {mesh_path}")

Solves #12

[traversaro]

Can't we just add a package_dirs vector of actual package directories in which to search?

In this way we can do:

mesh_path = resolve_robotics_uri(
    uri="package://example-robot-data/robots/ur_description/meshes/ur10/collision/shoulder.stl",
    package_dirs=get_package_dirs(import_module(f"robot_descriptions.ur10_description")),
)

as done in the rest of the robot_descriptions loaders in https://github.com/robot-descriptions/robot_descriptions.py/tree/d0dc260953a459450e73d9a4b456fd0b02ace59d/robot_descriptions/loaders ?

I think I know the answer to my question, but I want to understand your rationale.

[traversaro]

I think we should specify how the extra variable is interpreter. For example, if the uri is package://StrangeModel/Nested/mesh.st, and the actual mesh is in /usr/local/share/StrangeModel/Nested/mesh.stl, what should contain the extra path? /usr/local/share, /usr/local or /usr/local/share/StrangeModel. In theory we should also explicitly document how we interpret all the env variables listed here, but that is a more mitigated problems as they are documented in their respective projects, while the extra_path is something we add only here.

[flferretti]

Addressed in 2633149

[flferretti]

Yes it totally makes sense, I'll do the modification

[flferretti]

Ready for review after applying your suggestion in c1000b7. Thanks a lot!

[traversaro]

Thanks @flferretti ! I release v0.3.0 .