Simplify PlacementResult

[zhx06]

Summary

Unify PlacementResult and MultiEnvPlacementResult

Detailed description

• Remove MultiEnvPlacementResult
• Update related code and tests

[greptile-apps]

Greptile Summary

This PR unifies PlacementResult and MultiEnvPlacementResult by deleting the wrapper class and making ObjectPlacer.place() always return list[PlacementResult] — one element per environment — regardless of whether num_envs is 1 or greater.

• MultiEnvPlacementResult is fully removed; no remaining references exist in the codebase.
• Single-env call sites are updated to use tuple-unpacking ((result,) = placer.place(...)) and multi-env sites switch from result.results[i] to result[i].
• A new test_placement_result.py covers PlacementResult.success in isolation.

Confidence Score: 5/5

Safe to merge — all in-repo callers are updated, MultiEnvPlacementResult has no remaining references, and the simplified list return is consistent throughout.

The change removes a wrapper class and flattens the return type to always be a plain list. Every call site in tests, notebooks, and the pooled placer has been updated. No remaining references to MultiEnvPlacementResult exist anywhere in the repository, and the new test_placement_result.py provides focused coverage of the remaining PlacementResult.success logic.

No files require special attention.

Important Files Changed

Filename	Overview
isaaclab_arena/relations/placement_result.py	MultiEnvPlacementResult removed; PlacementResult kept unchanged as the single per-env result type.
isaaclab_arena/relations/object_placer.py	place() return type simplified from PlacementResult
isaaclab_arena/relations/pooled_object_placer.py	isinstance(result, MultiEnvPlacementResult) guard removed; place() result used directly as a list.
isaaclab_arena/tests/test_placement_result.py	New unit tests for PlacementResult.success covering required-pass, required-fail, and optional-fail scenarios.
isaaclab_arena/tests/test_heterogeneous_placement.py	isinstance(result, MultiEnvPlacementResult) assertions replaced with len(result) checks; result.results[i] replaced with result[i].

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["ObjectPlacer.place(objects, num_envs)"] --> B["_place_ranked() → ranked_results_per_env"]
    B --> C["results_per_env = [env[0] for env in ranked]"]
    C --> D["return results_per_env  ← list[PlacementResult]"]

    D --> E1["Single-env caller\n(result,) = placer.place(...)"]
    D --> E2["Multi-env caller\nfor r in placer.place(..., num_envs=N)"]
    D --> E3["PooledObjectPlacer\nall_layouts = placer.place(..., num_envs=batch)"]

    style D fill:#22c55e,color:#fff
    style E1 fill:#3b82f6,color:#fff
    style E2 fill:#3b82f6,color:#fff
    style E3 fill:#3b82f6,color:#fff

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%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
flowchart TD
    A["ObjectPlacer.place(objects, num_envs)"] --> B["_place_ranked() → ranked_results_per_env"]
    B --> C["results_per_env = [env[0] for env in ranked]"]
    C --> D["return results_per_env  ← list[PlacementResult]"]

    D --> E1["Single-env caller\n(result,) = placer.place(...)"]
    D --> E2["Multi-env caller\nfor r in placer.place(..., num_envs=N)"]
    D --> E3["PooledObjectPlacer\nall_layouts = placer.place(..., num_envs=batch)"]

    style D fill:#22c55e,color:#fff
    style E1 fill:#3b82f6,color:#fff
    style E2 fill:#3b82f6,color:#fff
    style E3 fill:#3b82f6,color:#fff

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_{Reviews (4): Last reviewed commit: "remove multi-env" | Re-trigger Greptile}

[alexmillane]

Thanks for the clean up!