fix SurfaceGripper.update

[sfetzel]

Description

Example scripts/demos/pick_and_place.py fails with error:

Traceback (most recent call last):
  File "/home/simonf9/Projects/isaaclab/IsaacLab/scripts/demos/pick_and_place.py", line 411, in <module>
    main()
  File "/home/simonf9/Projects/isaaclab/IsaacLab/scripts/demos/pick_and_place.py", line 401, in main
    pick_and_place = PickAndPlaceEnv(PickAndPlaceEnvCfg())
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/simonf9/Projects/isaaclab/IsaacLab/scripts/demos/pick_and_place.py", line 127, in __init__
    super().__init__(cfg, render_mode, **kwargs)
  File "/home/simonf9/Projects/isaaclab/IsaacLab/source/isaaclab/isaaclab/envs/direct_rl_env.py", line 167, in __init__
    self.scene.update(dt=self.physics_dt)
  File "/home/simonf9/Projects/isaaclab/IsaacLab/source/isaaclab/isaaclab/scene/interactive_scene.py", line 493, in update
    surface_gripper.update(dt)
  File "/home/simonf9/Projects/isaaclab/IsaacLab/source/isaaclab/isaaclab/assets/surface_gripper/surface_gripper.py", line 179, in update
    self._gripper_state = torch.tensor(state_list, dtype=torch.float32, device=self._device)
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: too many dimensions 'str'

Fixes issue #3893: GripperView.get_surface_gripper_status() returns list[str], not list[int]

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist

• [X ] I have read and understood the contribution guidelines
• [ X] I have run the pre-commit checks with ./isaaclab.sh --format
• [X ] I have made corresponding changes to the documentation
• [ X] 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
• I have added my name to the CONTRIBUTORS.md or my name already exists there. I guess that's not necessary.

[greptile-apps]

Greptile Overview

Greptile Summary

Fixed type mismatch bug in SurfaceGripper.update() where GripperView.get_surface_gripper_status() returns list[str] but was incorrectly typed as list[int] and directly converted to tensor, causing ValueError: too many dimensions 'str'.

Key changes:

• Corrected type annotation from list[int] to list[str] on surface_gripper.py:178
• Added explicit string-to-float mapping dictionary ({"Open": -1.0, "Closing": 0.0, "Closed": 1.0})
• Implemented proper conversion using map() before tensor creation
• Updated documentation comments to remove incorrect state-to-int mappings

Impact:

• Resolves runtime crash in scripts/demos/pick_and_place.py and other code using SurfaceGripper
• Maintains same numerical output values (-1.0, 0.0, 1.0) for neural network compatibility

Confidence Score: 4/5

• Safe to merge with minor consideration for error handling
• Fix correctly addresses the root cause (type mismatch) and maintains expected behavior. One minor improvement suggested: add error handling for unexpected state values to prevent potential KeyError exceptions
• No files require special attention - single file change is well-contained

Important Files Changed

File Analysis

Filename	Score	Overview
source/isaaclab/isaaclab/assets/surface_gripper/surface_gripper.py	4/5	Fixed type annotation and string-to-float conversion logic for gripper state; potential KeyError if unexpected state value returned

Sequence Diagram

sequenceDiagram
    participant ENV as Environment/Scene
    participant SG as SurfaceGripper
    participant GV as GripperView (Isaac Sim)
    participant TORCH as PyTorch Tensor
    
    Note over ENV,TORCH: Every simulation step
    ENV->>SG: update(dt)
    SG->>GV: get_surface_gripper_status()
    GV-->>SG: list[str] ["Open", "Closing", "Closed"]
    Note over SG: OLD: tried to convert list[str] to tensor directly (ValueError)
    Note over SG: NEW: map strings to floats using dictionary
    SG->>SG: map("Open" -> -1.0, "Closing" -> 0.0, "Closed" -> 1.0)
    SG->>TORCH: tensor(state_values, dtype=float32)
    TORCH-->>SG: gripper_state tensor
    Note over SG: State now usable for NN/RL

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[greptile-apps]

Greptile Overview

Greptile Summary

Fixes runtime error in SurfaceGripper.update() where GripperView.get_surface_gripper_status() returns list[str] but code incorrectly tried to convert strings directly to tensor and subtract 1.0.

Key changes:

• Corrected type annotation from list[int] to list[str] on line 178
• Added explicit string-to-float mapping dictionary for the three gripper states
• Used map() with mapping.get(s, 0.0) to convert state strings to numeric values
• Updated docstring comments to remove misleading numeric mappings (lines 165-167)

Analysis:
The fix correctly handles the API contract where Isaac Sim's GripperView returns string states ("Open", "Closing", "Closed") rather than integers. The use of .get() with a default value of 0.0 provides fallback handling if an unexpected state is returned, which maps to "Closing" behavior. This is a reasonable default that won't trigger immediate gripper actions.

Confidence Score: 4/5

• Safe to merge - fixes critical runtime bug with correct type handling
• The fix directly addresses the root cause of the ValueError by properly converting string states to floats. The mapping is consistent with documented behavior and the fallback default is sensible. Minor deduction for using silent default (0.0) instead of raising an error for unexpected states, though this is acceptable for robustness.
• No files require special attention

Important Files Changed

File Analysis

Filename	Score	Overview
source/isaaclab/isaaclab/assets/surface_gripper/surface_gripper.py	4/5	Fixes type error by converting string states from get_surface_gripper_status() to floats using explicit mapping instead of incorrect arithmetic. Uses .get() with default 0.0 for unknown states.

Sequence Diagram

sequenceDiagram
    participant Demo as pick_and_place.py
    participant Scene as InteractiveScene
    participant SG as SurfaceGripper
    participant GV as GripperView (Isaac Sim)
    
    Demo->>Scene: scene.update(dt)
    Scene->>SG: surface_gripper.update(dt)
    SG->>GV: get_surface_gripper_status()
    GV-->>SG: ["Open", "Closing", "Closed"]
    Note over SG: OLD: torch.tensor(state_list) - 1.0<br/>❌ Fails with "too many dimensions 'str'"
    Note over SG: NEW: Map strings to floats<br/>{"Open": -1.0, "Closing": 0.0, "Closed": 1.0}
    SG->>SG: state_values = [map states to floats]
    SG->>SG: _gripper_state = torch.tensor(state_values)
    SG-->>Scene: ✓ Update complete
    Scene-->>Demo: ✓ Scene updated

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