Refactor: Java comparator result handling into focused helpers

[shreejaykurhade]

This PR refactors compare_test_results in codeflash/languages/java/comparator.py to reduce local complexity without changing comparison behavior. Issue #526

The original function handled several responsibilities in one place:

• Java/runtime and SQLite path validation
• comparator subprocess execution
• comparator JSON parsing and stderr handling
• translation of comparator diffs into TestDiff objects
• final equivalence/summary validation and logging

That made the function harder to review and harder to modify safely, especially in a path that mixes subprocess failure handling with result translation.

What Changed

The result-handling portion of compare_test_results is now split into focused private helpers:

• _parse_comparator_output
  Validates stdout, parses the JSON payload, and preserves the existing stderr/debug logging behavior.

• _build_test_diffs
  Converts the Java comparator’s diff payload into TestDiff objects and keeps the per-diff debug logging in one place.

• _finalize_comparison_result
  Applies the final summary validation (actualComparisons, skipped placeholder/deserialization counts) and centralizes the final equivalence logging.

compare_test_results now acts as the orchestration layer for:

• prerequisite validation
• Java comparator execution
• error short-circuiting
• output parsing
• diff construction
• final result selection

Why This Is Better

This improves maintainability by:

• reducing the responsibility surface of the main comparator entry point
• separating subprocess/output concerns from domain-level diff construction
• making the comparison flow easier to scan top-to-bottom
• lowering the risk of future changes to JSON parsing or diff translation accidentally affecting subprocess/error handling

This is intended to be a behavior-preserving refactor, not a comparison-logic change.

Behavior / Compatibility

No comparison behavior is intended to change.

In particular, this refactor preserves:

• Java executable / runtime JAR validation
• existing subprocess invocation and timeout behavior
• empty-output and malformed-JSON handling
• error handling for comparator-provided JSON errors
• exit-code validation
• TestDiff construction rules
• the actualComparisons == 0 safeguard
• existing summary/debug logging semantics

Validation

uv run pytest -q tests/test_languages/test_java/test_comparator.py
uv run ruff check codeflash/languages/java/comparator.py

Results:

• 76 passed
• ruff passed

Risk

Low.

This is a structural refactor in a well-covered module with dedicated Java comparator tests already in place. The refactor preserves the original execution order and error handling while only extracting cohesive result-processing steps.

[shreejaykurhade]

@Saga4 @KRRT7 please review.

[KRRT7]

@shreejaykurhade hi, thanks for the PRs, can you hold off on future PRs? let me come up with issues and context so that you're better able to help us