Update usage of HashlessObject in JaxSimModel

src/jaxsim/api/frame.py

@@ -30,7 +30,7 @@ def idx_of_parent_link(model: js.model.JaxSimModel, *, frame_idx: jtp.IntLike) -
     """
 
     # Get the intermediate representation parsed from the model description.
-    ir = model.description.get()
+    ir = model.description
 
     # Extract the indices of the frame and the link it is attached to.
     F = ir.frames[frame_idx - model.number_of_links()]
@@ -51,7 +51,7 @@ def name_to_idx(model: js.model.JaxSimModel, *, frame_name: str) -> int:
         The index of the frame.
     """
 
-    frame_names = np.array([frame.name for frame in model.description.get().frames])
+    frame_names = np.array([frame.name for frame in model.description.frames])
 
     if frame_name in frame_names:
         idx_in_list = np.argwhere(frame_names == frame_name)
@@ -72,7 +72,7 @@ def idx_to_name(model: js.model.JaxSimModel, *, frame_index: jtp.IntLike) -> str
         The name of the frame.
     """
 
-    return model.description.get().frames[frame_index - model.number_of_links()].name
+    return model.description.frames[frame_index - model.number_of_links()].name
 
 
 @functools.partial(jax.jit, static_argnames=["frame_names"])
@@ -144,7 +144,7 @@ def transform(
     W_H_L = js.link.transform(model=model, data=data, link_index=L)
 
     # Get the static frame pose wrt the parent link.
-    frame = model.description.get().frames[frame_index - model.number_of_links()]
+    frame = model.description.frames[frame_index - model.number_of_links()]
     L_H_F = frame.pose
 
     # Combine the transforms computing the frame pose.

src/jaxsim/api/model.py

@@ -32,18 +32,21 @@ class JaxSimModel(JaxsimDataclass):
     terrain: Static[jaxsim.terrain.Terrain] = dataclasses.field(
         default=jaxsim.terrain.FlatTerrain(), repr=False, compare=False, hash=False
     )
+    kin_dyn_parameters: js.kin_dyn_parameters.KynDynParameters | None = (
+        dataclasses.field(default=None, repr=False, compare=False, hash=False)
+    )
 
     built_from: Static[str | pathlib.Path | rod.Model | None] = dataclasses.field(
         default=None, repr=False, compare=False, hash=False
     )
 
-    description: Static[
+    _description: Static[
         HashlessObject[jaxsim.parsers.descriptions.ModelDescription | None]
     ] = dataclasses.field(default=None, repr=False, compare=False, hash=False)
 
-    kin_dyn_parameters: js.kin_dyn_parameters.KynDynParameters | None = (
-        dataclasses.field(default=None, repr=False, compare=False, hash=False)
-    )
+    @property
+    def description(self) -> jaxsim.parsers.descriptions.ModelDescription:
+        return self._description.get()
 
     def __eq__(self, other: JaxSimModel) -> bool:
 
@@ -153,7 +156,7 @@ def build(
         # Build the model
         model = JaxSimModel(
             model_name=model_name,
-            description=HashlessObject(obj=model_description),
+            _description=HashlessObject(obj=model_description),
             kin_dyn_parameters=js.kin_dyn_parameters.KynDynParameters.build(
                 model_description=model_description
             ),
@@ -276,7 +279,7 @@ def frame_names(self) -> tuple[str, ...]:
             The names of the links in the model.
         """
 
-        return tuple([frame.name for frame in self.description.get().frames])
+        return tuple([frame.name for frame in self.description.frames])
 
 
 # =====================
@@ -313,7 +316,7 @@ def reduce(
 
     # Copy the model description with a deep copy of the joints.
     intermediate_description = dataclasses.replace(
-        model.description.get(), joints=copy.deepcopy(model.description.get().joints)
+        model.description, joints=copy.deepcopy(model.description.joints)
     )
 
     # Update the initial position of the joints.

tests/test_api_frame.py

@@ -17,12 +17,10 @@ def test_frame_index(jaxsim_models_types: js.model.JaxSimModel):
     # =====
 
     frame_indices = tuple(
-        frame.index
-        for frame in model.description.get().frames
-        if frame.index is not None
+        frame.index for frame in model.description.frames if frame.index is not None
     )
 
-    frame_names = np.array([frame.name for frame in model.description.get().frames])
+    frame_names = np.array([frame.name for frame in model.description.frames])
 
     for frame_idx, frame_name in zip(frame_indices, frame_names):
         assert js.frame.name_to_idx(model=model, frame_name=frame_name) == frame_idx
@@ -60,7 +58,7 @@ def test_frame_transforms(
     # Get all names of frames in the iDynTree model.
     frame_names = [
         frame.name
-        for frame in model.description.get().frames
+        for frame in model.description.frames
         if frame.name in kin_dyn.frame_names()
     ]
 
@@ -74,7 +72,7 @@ def test_frame_transforms(
     # Get indices of frames.
     frame_indices = tuple(
         frame.index
-        for frame in model.description.get().frames
+        for frame in model.description.frames
         if frame.index is not None and frame.name in frame_names
     )
 
@@ -115,7 +113,7 @@ def test_frame_jacobians(
     # Get all names of frames in the iDynTree model.
     frame_names = [
         frame.name
-        for frame in model.description.get().frames
+        for frame in model.description.frames
         if frame.name in kin_dyn.frame_names()
     ]
 
@@ -127,7 +125,7 @@ def test_frame_jacobians(
     # Get indices of frames.
     frame_indices = tuple(
         frame.index
-        for frame in model.description.get().frames
+        for frame in model.description.frames
         if frame.index is not None and frame.name in frame_names
     )
 

tests/utils_idyntree.py

@@ -52,7 +52,7 @@ def build_kindyncomputations_from_jaxsim_model(
     # Get the default positions already stored in the model description.
     removed_joint_positions_default = {
         str(j.name): float(j.initial_position)
-        for j in model.description.get()._joints_removed
+        for j in model.description._joints_removed
         if j.name not in considered_joints
     }