feat(js): add JavaScript function tracer with Babel instrumentation #1377
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⚡️ Codeflash found optimizations for this PR📄 18% (0.18x) speedup for
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![claude[bot]](https://avatars.githubusercontent.com/in/1236702?s=60&v=4){kind=small}
| logger.info("Running JavaScript tracer: %s", " ".join(cmd)) | ||
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| try: | ||
| process = subprocess.run(cmd, cwd=project_root, env=env, capture_output=False, check=False) |
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capture_output=False, which makes debugging failures very difficult. When the tracer fails (non-zero exit code), there's no stdout/stderr available to diagnose the issue.
Suggested fix:
process = subprocess.run(cmd, cwd=project_root, env=env, capture_output=True, text=True, check=False)
if process.returncode != 0:
result["error"] = f"Tracing failed with exit code {process.returncode}\nStdout: {process.stdout}\nStderr: {process.stderr}"
| conn.close() | ||
| return functions | ||
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| except Exception: |
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Suggested fix:
except Exception as e:
logger.exception(f"Failed to get traced functions from {trace_file}: {e}")
return []
| sys.exit(1) | ||
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| console.print(f"[green]Trace saved to: {result['trace_file']}[/green]") | ||
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✅ Acknowledged: The JavaScript tracer automatically triggers optimization without explicit user consent when not in trace-only mode. This is acceptable as it matches the intended workflow and is documented through the CLI flags.
| from codeflash.languages.javascript.tracer import JavaScriptTracer | ||
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| def node_available() -> bool: |
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💡 Consider adding helper: The E2E tests check for Node.js availability, but there's no helper to install npm dependencies. Consider adding a fixture that checks if node_modules/codeflash exists and provides setup instructions if missing.
PR Review Summary✅ Prek ChecksAll prek checks (ruff format, ruff check) passed successfully. No auto-fixable issues found.
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| File | Coverage (PR) | Coverage (Main) | Change | Status |
|---|---|---|---|---|
| replay_test.py (NEW) | 64% | N/A | +64% | |
| tracer_runner.py (NEW) | 34% | N/A | +34% | 🔴 Below 75% |
| tracer.py | 86% | N/A | +86% | ✅ Good |
| support.py | 74% | 74% | 0% | ✅ Maintained |
| parse_test_output.py | 42% | 59% | -17% |
Overall Coverage:
- Main branch: 79.4%
- PR branch: Unable to calculate due to deleted file in coverage data
- Test results: 8 failing tests (same failures exist on main branch - not introduced by this PR)
Concerns:
- 🔴 tracer_runner.py: Only 34% coverage - critical new functionality is undertested
⚠️ replay_test.py: 64% coverage - below recommended 75% threshold⚠️ parse_test_output.py: Coverage decreased from 59% to 42%
Recommendation: Add more unit tests for tracer_runner.py and replay_test.py to improve coverage above 75% threshold.
Last updated: 2026-02-05 17:51 UTC
Review by Claude Code Bot
⚡️ Codeflash found optimizations for this PR📄 67% (0.67x) speedup for
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Add Babel-based function tracing for JavaScript/TypeScript: - tracer.js: Core tracer with SQLite storage and nanosecond timing - babel-tracer-plugin.js: AST transformation to wrap functions - trace-runner.js: Entry point for running traced code - replay.js: Utilities for replay test generation - Update package.json with exports and dependencies
Add Python modules for JavaScript tracing orchestration: - replay_test.py: Generate Jest/Vitest replay tests from traces - tracer_runner.py: Run trace-runner.js and detect test frameworks - tracer.py: Refactored to use Babel-only approach, removed legacy source transformation code
Move Jest/Vitest JUnit XML parsing from separate module into the main parse_test_output.py file to reduce module fragmentation. Remove duplicate tests that were testing the now-deleted module.
Add language detection and routing to JavaScript tracer in the main tracer CLI. Supports --language flag and auto-detection from file extensions in project.
Add comprehensive test coverage for JavaScript tracing: - Unit tests for trace parsing (function_calls and legacy schemas) - Unit tests for replay test generation (Jest and Vitest) - E2E test for full tracing pipeline with npm dependencies - Framework detection tests (Jest, Vitest, package.json)
- Add explicit type annotations for json.load return values - Annotate result dict with dict[str, Any] - Add type hints for config parameters - Fix pytest_split unpacking to satisfy type checker - Add null check for outfile before passing to run_javascript_tracer_main Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
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| console.log('[codeflash] Running Vitest with tracing...'); | ||
| console.log('[codeflash] Note: ESM tracing requires additional setup. See documentation.'); |
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How are we implementing this as its quite common to have vitest with esm in current times.
| const config = parseArgs(args); | ||
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| // Register Babel with tracer plugin | ||
| registerBabel(config); |
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Trying to understand how this will work when the transformation of codebases in vitest/webpack or esbuild happens before registering babel.
We might need more examples/tests with vitest and esm compatibility.
2 participants
Summary
--languageflag and auto-detectionChanges
Test plan
test_javascript_tracer.pyjs-tests.ymlGitHub Actions workflow