Use Case: facebook/react - The React Library

Repository: https://github.com/facebook/react Stack: TypeScript/JavaScript (JSX/TSX) Test Date: 2025-12-08 Loctree Version: 0.6.2-dev

Overview

Testing loctree on THE React library source - the definitive test for JSX/TSX analysis.

Repository Scale

Metric	Value
Files Scanned	3,951
Analysis Time	49 seconds
Throughput	81 files/sec
Artifacts Generated	33 MB

Performance

Metric	Value
Scan Time	49.02 seconds
Dead Exports Found	676
Dead Parrots	1,684
Circular Dependencies	8 cycles

Findings

Dead Code Detection

High Confidence: 676 candidates
False Positive Rate: ~20%
True Positives: Compiler internals, experimental features, legacy dev tools

False Positive Categories (v0.6.x Improvements)

Import aliasing (import {X as Y}) - ~10-15% (improved tracking)
Type-only exports in .js files - ~5% (better Flow type detection)
Global registries (WeakMap/Set patterns) - ~5% (registry pattern detection added)

Circular Dependencies

✓ Found 8 circular import cycles

Notable findings:

Massive compiler cycle: 115 files in babel-plugin-react-compiler
DevTools store ↔ cache co-dependency
DOM event system ↔ priority scheduler
Reconciler lanes ↔ DevTools hooks

True Dead Code Found

babel-plugin-react-compiler internal utilities (~200 exports)
Experimental ReactServer features (Activity, ViewTransition)
Dev-only tools (console patching, debug prints)
Unused type helpers in Flow integration

Commands Used

cd react
loct                              # Create snapshot
loct dead --confidence high       # Dead code analysis
loct cycles                       # Circular dependencies
loct twins                        # Duplicate detection

Verdict

A- PASSED - Production-ready with significantly improved dead code accuracy (v0.6.x).

Grade Card

Category	Grade	v0.6.x Improvements
Performance	A+	No change
JSX/TSX Support	A	WeakMap/WeakSet patterns
Dead Code Accuracy	B+	40% → 20% FP rate
Cycle Detection	A	No change
Scalability	A+	No change

Recommended Workflow

loct dead --confidence high > candidates.txt
# Verify top 50 with ripgrep
# Delete exports with 0 matches (safe)
# Review exports with only type matches