Simplify Arena Experiment result collection

[cvolkcvolk]

Summary

Simplify Arena Experiment result collection

Detailed description

• Follow up on Write one combined JSON result for each Arena Experiment #1070 by keeping ArenaExperimentResult focused on combining declared Run outputs while preserving the completed-Run directory check.
• Rename the configuration conversion to describe its exact output: environment fields and policy_variant.
• Document when that conversion can be removed. The generated JSON format does not change.

Verified with the full pre-commit suite and 54 focused result, local runner, and OSMO tests.

[greptile-apps]

Greptile Summary

This PR simplifies Arena Experiment result collection while retaining completed-Run directory validation and renames the configuration conversion helper to describe its output precisely.

• Collects declared environment metadata directly and discovers rebuilds uniformly.
• Renames the environment and policy-variant conversion across local and OSMO execution paths.
• Updates focused tests and documents when the compatibility conversion can be removed.

Confidence Score: 4/5

The PR appears safe to merge, with a non-blocking opportunity to retain validation of the serialized Run-status contract.

Current production callers obtain statuses from the completed/failed enum, while the simplified collector now permits schema-invalid statuses from direct callers and may cause those Runs to disappear from report classification.

Files Needing Attention: isaaclab_arena/evaluation/arena_experiment_result.py

Important Files Changed

Filename	Overview
isaaclab_arena/evaluation/arena_experiment_result.py	Simplifies Run result collection and renames metadata conversion, but removes runtime validation of the declared status domain.
isaaclab_arena/evaluation/experiment_runner.py	Updates the local result-writing path to use the renamed conversion helper without changing generated metadata.
osmo/tasks/experiment_runner_task.py	Updates OSMO metadata generation to use the renamed helper while preserving the JSON shape.
isaaclab_arena/tests/test_arena_experiment_result.py	Renames conversion tests consistently; existing coverage confirms missing failed-Run directories still produce empty rebuild lists.

_{Reviews (1): Last reviewed commit: "Simplify Arena Experiment result collect..." | Re-trigger Greptile}

[greptile-apps]

Validate the Run status domain

ArenaExperimentRunData restricts status to completed or failed, but _collect_run now serializes any supplied value. An invalid status therefore produces schema-invalid output and prevents downstream reports from classifying the Run as either completed or failed.

Suggested change

	status = run_metadata["status"]
	assert (
	status != "completed" or run_output_directory.is_dir()
	), f"completed Run {run_name!r} is missing its output directory: {run_output_directory}"
	status = run_metadata["status"]
	assert status in ("completed", "failed"), f"status for Run {run_name!r} must be 'completed' or 'failed'"
	assert (
	status != "completed" or run_output_directory.is_dir()
	), f"completed Run {run_name!r} is missing its output directory: {run_output_directory}"

[arena-review-bot]

🤖 Isaac Lab-Arena Review Bot

Summary

Clean, well-scoped follow-up to #1070. It trims _collect_run down to two asserts plus an unconditional _collect_rebuilds, passes the environment field straight through instead of rebuilding it, and renames build_arena_run_result_metadata → run_environment_and_policy_variant_from_config with TODOs marking when the conversion can be retired. I verified the simplifications are behavior-preserving and the tests cover them.

Findings

No blocking issues. A few things I checked that hold up:

• Dropping the if run_output_directory.is_dir() else [] guard is safe — find_episode_results_files globs via Path.rglob, which yields nothing (no error) on a missing path, so a failed Run without a directory still collects []. Exercised by test_failed_runs_may_have_empty_or_missing_output_directories.
• Removing assert status in ("completed", "failed") is fine — every producer feeds RunStatus.value, and RunStatus only has those two members, so the check was redundant. Passing run_metadata["environment"] through instead of reconstructing {name, definition} is likewise contract-enforced by the ArenaExperimentRunData TypedDict and the single producer.
• The hasattr(env_spec_path) / getattr(policy_variant) branches in the renamed function are pre-existing and now documented with removal TODOs — out of scope here.

Test Coverage

Good. The renamed conversion tests still assert the exact output for both the graph-YAML and registered-config paths, and the collection tests cover completed-requires-directory, failed-with-missing/empty-directory, unsafe run names, and malformed JSONL. No new code paths go untested.

Verdict

Ship it