`FrameCollisionResidual(ndx, nu, model, collision_model, 0)` leads to segfault when collision_model has no collision pairs

[oomcth]

When using aligator.FrameCollisionResidual(ndx, nu, model, collision_model, 0) with a collision_model that contains no collision pairs, it results in a segmentation fault.

It is expected to get an error when collision model has no collision pairs but a message could help debug.

@edantec

[ManifoldFR]

Hello, could you provide a minimal example for this? Or add this case to the relevant test for the FrameCollisionResidual class in a pull request? If you do the latter, I'll piggyback on that pull request to fix the bug.

[oomcth]

I did this by editing this file : https://github.com/Simple-Robotics/aligator/blob/main/examples/ur5_reach.py
If you take https://github.com/Simple-Robotics/aligator/blob/main/examples/ur5_reach.py and just comment line 58 : geometry.addCollisionPair(pin.CollisionPair(ig_frame, ig_frame2)) and set args.collisions = True then you get the segfault.
The bellow code is just https://github.com/Simple-Robotics/aligator/blob/main/examples/ur5_reach.py with this 58th line (now 37th line) commented and non relevant lines deleted.

import aligator
import numpy as np

import pinocchio as pin
import example_robot_data as erd
import matplotlib.pyplot as plt
import matplotlib.gridspec as gridspec

from aligator import constraints, manifolds, dynamics  # noqa
from pinocchio.visualize import MeshcatVisualizer
import hppfcl


robot = erd.load("ur5")
rmodel: pin.Model = robot.model
rdata: pin.Data = robot.data
space = manifolds.MultibodyPhaseSpace(rmodel)

fr_name = "universe"
fr_id = rmodel.getFrameId(fr_name)
joint_id = rmodel.frames[fr_id].parentJoint
obstacle_loc = pin.SE3.Identity()
geom_object = pin.GeometryObject(
    "capsule", fr_id, joint_id, hppfcl.Capsule(0.05, 0.4), obstacle_loc
)

fr_id2 = rmodel.getFrameId("wrist_3_joint")
joint_id2 = rmodel.frames[fr_id2].parentJoint
geom_object2 = pin.GeometryObject(
    "endeffector", fr_id2, joint_id2, hppfcl.Sphere(0.1), pin.SE3.Identity()
)

geometry = pin.GeometryModel()
ig_frame = geometry.addGeometryObject(geom_object)
ig_frame2 = geometry.addGeometryObject(geom_object2)
# Commenting the bellow line causes the issue as now geometry.n_collision_pairs is 0
# geometry.addCollisionPair(pin.CollisionPair(ig_frame, ig_frame2))

ndx = space.ndx
nu = rmodel.nv

# This line causes the segfault
frame_col = aligator.FrameCollisionResidual(ndx, nu, rmodel, geometry, 0)

[ManifoldFR]

To clarify @oomcth -- the test doesn't need to pass for the PR. I just need the code in an appropriate Python test file (under tests/python/... in one of the existing test files most likely. maybe test_frames.py). Since it triggers a segfault, the test will not pass and I will have an entry point for fixing the issue, adding a proper exception, etc.

[ManifoldFR]

Fixed by #294. Fix now available in aligator v0.13.0 !