Replaces IsaacSim `stage_utils` with IsaacLab `stage_utils`

[pascal-roth]

Description

Remove dependency on IsaacSim stage_utils for integration of new simulation engines like newton.

Type of change

• Dependency removal

Checklist

• [ ] I have read and understood the contribution guidelines
• [ ] I have run the pre-commit checks 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
• [ ] I have added my name to the CONTRIBUTORS.md or my name already exists there

[ooctipus]

Seems like many things are failing :eyes:

[ooctipus]

I looked into the failing issue it seems like because we are combining from utils import * with cross package import. If you changes import isaaclab.sim.utils.stage as stage_utils to from isaaclab.sim.utils import stage as stage_utils

it will work again, Explaination:

from utils import * rebinds names on the parent package, and in your case it ends up binding isaaclab.sim.utils to the module isaaclab.sim.utils.utils instead of the utils package. import isaaclab.sim.utils.stage as stage_utils requires isaaclab.sim.utils to be a package (with path) so it can descend to stage, which fails when it’s actually the module. from isaaclab.sim.utils import stage as stage_utils works because it imports the package and then accesses its stage attribute directly, bypassing that package-versus-module mix-up.

Personally I think that the root cause is import * in init.py files. It blindly rebinds names and can shadow the package object (isaaclab.sim.utils) with a module (utils.py), breaking dotted imports like import isaaclab.sim.utils.stage as ….

In the new rework we may need to consider to drop * import all together (at least for core)

[greptile-apps[bot]]

Greptile Overview

Greptile Summary

This PR successfully removes the IsaacLab dependency on IsaacSim's stage_utils module by implementing its own stage.py utility module. This enables integration with alternative simulation engines like Newton.

Key Changes:

• Created new isaaclab/sim/utils/stage.py with ~800 lines implementing stage management functions
• Refactored utils.py to import and re-export key functions from the new stage.py module, maintaining backward compatibility
• Updated 50+ files across the codebase to import from IsaacLab's stage utilities instead of IsaacSim's
• The new implementation includes proper Isaac Sim version checks and fallbacks for compatibility

Implementation Quality:

• Clean separation of concerns with stage utilities in dedicated module
• Proper thread-local storage pattern for concurrent stage access
• Comprehensive error handling and version compatibility checks
• Backward compatibility maintained through re-exports in utils.py

The migration is comprehensive and well-executed. All test files have been updated appropriately, and the changelog documents the change.

Confidence Score: 5/5

• This PR is safe to merge - it's a clean dependency removal with comprehensive test coverage and backward compatibility
• The PR achieves its goal of removing IsaacSim dependency on stage_utils with a well-structured implementation. The new stage.py module properly implements all necessary functions with version checks and error handling. All imports across 50+ files have been systematically updated. Backward compatibility is maintained through re-exports. No logical errors or breaking changes detected.
• No files require special attention - the implementation is solid throughout

Important Files Changed

File Analysis

Filename	Score	Overview
source/isaaclab/isaaclab/sim/utils/stage.py	5/5	New file implementing IsaacLab's own stage utilities, replacing IsaacSim dependency. Clean implementation with proper error handling and version checks.
source/isaaclab/isaaclab/sim/utils/utils.py	5/5	Refactored to remove stage utility functions and import them from new stage.py module. Maintains backward compatibility through re-exports.
source/isaaclab/isaaclab/sim/simulation_context.py	5/5	Updated imports to use IsaacLab stage utilities instead of IsaacSim's. Clean migration with no logic changes.
source/isaaclab/isaaclab/scene/interactive_scene.py	5/5	Updated imports from IsaacSim stage utils to IsaacLab stage module. No functional changes.
source/isaaclab/test/sim/test_stage_in_memory.py	5/5	Test file updated to use IsaacLab stage utilities. All function calls properly migrated.

Sequence Diagram

sequenceDiagram
    participant User
    participant SimContext as SimulationContext
    participant StageUtils as isaaclab.sim.utils.stage
    participant IsaacSim as IsaacSim Core
    participant USD as USD Stage

    User->>SimContext: Initialize simulation
    SimContext->>StageUtils: create_new_stage_in_memory()
    StageUtils->>USD: Usd.Stage.CreateInMemory()
    USD-->>StageUtils: stage instance
    StageUtils-->>SimContext: stage instance
    
    User->>SimContext: Setup scene
    SimContext->>StageUtils: use_stage(stage_in_memory)
    StageUtils->>StageUtils: Set thread-local stage context
    
    User->>SimContext: Attach stage for rendering
    SimContext->>StageUtils: attach_stage_to_usd_context()
    StageUtils->>StageUtils: Check if stage is in memory
    StageUtils->>IsaacSim: physx_sim_interface.attach_stage()
    StageUtils->>IsaacSim: omni.usd.attach_stage_with_callback()
    IsaacSim-->>StageUtils: Stage attached
    
    User->>SimContext: Query stage state
    SimContext->>StageUtils: is_current_stage_in_memory()
    StageUtils->>USD: get_current_stage_id()
    StageUtils->>IsaacSim: omni.usd.get_context().get_stage()
    StageUtils-->>SimContext: boolean result

[pascal-roth]

@ooctipus I think for this one we are also ready to go