Adds dict conversion test for ActuatorBase configs (isaac-sim#1608)

# Description

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A recent PR
(isaac-sim#1530 (comment))
causes issues with joint_parameter_lookup attributes of Articulation
Configs. The `class_to_dict` utility function needs to return a
primitive dict. Returning a torch.Tensor conflicts with OmegaConf.

This PR adds a unittest for the dict conversion as requested by @lgulich
so that the issue can be fixed. The test case fails on main branch as
expected according to my understanding. Passes on v1.3.0.

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## Type of change

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- Breaking change (fix or feature that would cause existing
functionality to not work as expected)

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## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

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.pre-commit-config.yaml

@@ -45,6 +45,7 @@ repos:
       - id: codespell
         additional_dependencies:
         - tomli
+        exclude: "CONTRIBUTORS.md"
   # FIXME: Figure out why this is getting stuck under VPN.
   # - repo: https://github.com/RobertCraigie/pyright-python
   #   rev: v1.1.315

CONTRIBUTORS.md

@@ -62,6 +62,7 @@ Guidelines for modifications:
 * Lionel Gulich
 * Louis Le Lay
 * Lorenz Wellhausen
+* Manuel Schweiger
 * Masoud Moghani
 * Michael Gussert
 * Michael Noseworthy

source/extensions/omni.isaac.lab/test/utils/test_configclass.py

@@ -143,6 +143,16 @@ class BasicDemoTorchCfg:
     some_tensor: torch.Tensor = torch.Tensor([1, 2, 3])
 
 
+@configclass
+class BasicActuatorCfg:
+    """Dummy configuration class for ActuatorBase config."""
+
+    joint_names_expr: list[str] = ["some_string"]
+    joint_parameter_lookup: list[list[float]] = [[1, 2, 3], [4, 5, 6]]
+    stiffness: float = 1.0
+    damping: float = 2.0
+
+
 """
 Dummy configuration to check type annotations ordering.
 """
@@ -530,6 +540,18 @@ def test_dict_conversion(self):
         self.assertEqual(torch_cfg_dict["some_number"], 0)
         self.assertTrue(torch.all(torch_cfg_dict["some_tensor"] == torch.tensor([1, 2, 3])))
 
+    def test_actuator_cfg_dict_conversion(self):
+        """Test dict conversion of ActuatorConfig."""
+        # create a basic RemotizedPDActuator config
+        actuator_cfg = BasicActuatorCfg()
+        # return writable attributes of config object
+        actuator_cfg_dict_attr = actuator_cfg.__dict__
+        # check if __dict__ attribute of config is not empty
+        self.assertTrue(len(actuator_cfg_dict_attr) > 0)
+        # class_to_dict utility function should return a primitive dictionary
+        actuator_cfg_dict = class_to_dict(actuator_cfg)
+        self.assertTrue(isinstance(actuator_cfg_dict, dict))
+
     def test_dict_conversion_order(self):
         """Tests that order is conserved when converting to dictionary."""
         true_outer_order = ["device_id", "env", "robot_default_state", "list_config"]