Fix: Recalculate js_project_root per function in monorepos

[mohammedahmed18]

Issue

When optimizing multiple functions in a monorepo with nested package.json files (e.g., extensions/discord/package.json), the js_project_root was set once for the first function and reused for all subsequent functions. This caused vitest to fail with:

Error: Cannot find module '/workspace/target/extensions/discord/test/setup.ts'

Root Cause

• test_cfg.js_project_root was set during initial setup_test_config() call
• This value was cached and reused for ALL functions being optimized
• When function setup github actions #1 was in extensions/discord/, all subsequent functions in src/ inherited this wrong project root
• Vitest tried to resolve setupFiles: ["test/setup.ts"] relative to the wrong directory

Fix

• Added _get_js_project_root() method to FunctionOptimizer class
• Calculate js_project_root fresh for each function using find_node_project_root()
• Updated all test execution paths:
  • Behavioral tests (TestingMode.BEHAVIOR)
  • Performance tests (TestingMode.PERFORMANCE)
  • Line profiling tests (TestingMode.LINE_PROFILE)

Testing

• Added unit tests demonstrating the bug and verifying the fix
• All existing tests pass
• No lint/type errors (uv run prek passes)

Impact

• ✅ Vitest runs from the correct working directory for each function
• ✅ setupFiles can be resolved correctly
• ✅ Functions in different monorepo packages can be optimized without interference

Trace IDs Fixed

Affects ALL optimization runs where first function is in a subdirectory with its own package.json:

• 12d26b00-cbae-49a8-a3cd-c36024ee06ec
• 1cde1c65-ef42-4072-afbc-165b0c235688
• And 18 other traces in current batch

🤖 Generated with Claude Code

[claude]

Claude finished @mohammedahmed18's task in 5m 23s —— View job

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PR Review Summary

Prek Checks

One auto-fixable ruff issue was detected (D413: missing blank line after last docstring section) — committed and resolved.

Code Review

The fix is correct and addresses the root cause. A few convention issues were pushed as a follow-up commit:

Naming (fixed): _get_js_project_root used a leading underscore, violating the project convention from CLAUDE.md ("NEVER use leading underscores — Python has no true private functions, use public names"). Renamed to get_js_project_root.

Redundant import (fixed): from pathlib import Path at function_optimizer.py:3106 was re-imported inside the method body — Path is already imported at the top of the file (line 12). Removed.

Docstring on new method (fixed): CLAUDE.md says not to add docstrings to new or changed code. Removed.

_get_js_project_root() called 3 times (minor): The method is called once per TestingMode branch rather than once before the if-elif chain. This is a minor redundancy — each call re-traverses the filesystem. A single call before the branch would be cleaner, but since each call is fast and run_and_parse_tests handles only one branch per invocation, it's not a correctness issue.

Tests (fixed)

Both test files violated project testing conventions:

• Used tempfile.TemporaryDirectory() — must use tmp_path fixture per convention
• Missing .resolve() on Path objects before passing to functions under test
• Missing encoding="utf-8" on write_text() calls
• Unused import pytest in test_js_project_root_per_function.py

The second test file (test_optimizer_js_project_root_bug.py) contained an @pytest.mark.xfail test with an incorrect assumption: it expected that once the bug was "fixed", test_cfg.js_project_root would be updated. But the fix works by bypassing test_cfg in get_js_project_root(), not by changing what test_cfg stores. The xfail would have been a permanent XPASS. Rewrote the file to just demonstrate the caching behavior as a straightforward assertion.

Duplicate Detection

No duplicates detected.

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Changes pushed: e7596b5b — naming, imports, and test convention fixes.
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