Fix get_link_names exception for single-link groups (#160)

AUTHORS.md

@@ -17,3 +17,4 @@
 - Edvard Bruun <<ebruun@princeton.edu>> [@ebruun](https://github.com/ebruun)
 - Victor Pok Yin Leung <<leung@arch.ethz.ch>> [@yck011522](https://github.com/yck011522)
 - Begüm Saral <<begum.saral@tum.de>> [@begums](https://github.com/begums)
+- Swastik Verma <<swastikjee09@gmail.com>> [@Swastik-Verma](https://github.com/Swastik-Verma)

src/compas_fab/robots/robot_cell.py

@@ -450,8 +450,11 @@ def get_link_names(self, group: Optional[str] = None) -> list[str]:
         base_link_name = self.get_base_link_name(group)
         end_effector_link_name = self.get_end_effector_link_name(group)
         link_names = []
-        for link in self.robot_model.iter_link_chain(base_link_name, end_effector_link_name):
-            link_names.append(link.name)
+        if base_link_name is not None and base_link_name == end_effector_link_name:
+            link_names.append(base_link_name)
+        else:
+            for link in self.robot_model.iter_link_chain(base_link_name, end_effector_link_name):
+                link_names.append(link.name)
         return link_names
 
     def get_link_names_with_collision_geometry(self) -> list[str]:

tests/robots/test_robot_cell.py

@@ -178,6 +178,9 @@ def _test(rc: RobotCell, rcs: RobotCellState):
     _test(*rfl)
     _test(*ur10e_gripper_one_beam)
     _test(*abb_irb4600_40_255_gripper_one_beam)
+    robot_cell, robot_cell_state = ur10e_gripper_one_beam
+    link_names = robot_cell.get_link_names("endeffector")
+    assert link_names == ["tool0"]
 
 
 def test_default_touch_links_returns_first_geometry_bearing_link():