🚀 Major Parser Performance Optimizations for Large Xcode Projects

[maatheusgois-dd]

📋 Problem

The existing pbxproj parser crashed with heap out of memory errors on large projects like Test (94.81MB, 125K+ objects). The original JsonVisitor used expensive object spread operations ({...prev, ...item}) causing O(n²) complexity and excessive memory allocation.

⚡ Solution

Implemented multi-tier parsing optimizations with automatic strategy selection based on file size:

1. Optimized JsonVisitor (OptimizedJsonVisitor.ts)

• ✅ Eliminated object spread operations - Replaced with direct property assignment (O(n) complexity)
• ✅ Pre-allocated objects with known sizes to reduce memory allocations
• ✅ Cached common identifiers (isa, children, name, etc.) to reduce string creation
• ✅ Progress reporting for large files with memory pressure detection

2. Streaming Parser (StreamingJsonVisitor.ts)

• ✅ Chunked processing - Handles massive objects in 1K item chunks
• ✅ Memory management - Automatic garbage collection hints when memory pressure detected
• ✅ Deferred object processing to prevent memory buildup

3. Memory-Efficient Analyzer (MemoryEfficientVisitor.ts)

• ✅ Metadata extraction only - No full object tree construction
• ✅ Constant memory usage regardless of file size
• ✅ Essential statistics - File types, object counts, target names

4. Enhanced XcodeProject API

• ✅ XcodeProject.openLazy() - Skip expensive full object inflation
• ✅ Automatic strategy selection - Picks optimal parser based on file size
• ✅ Progress callbacks and memory monitoring

📊 Performance Results

Before vs After:

Project Size	Before	After	Improvement
0.10MB (AFNetworking)	7.80ms	3.84ms	51% faster 🚀
94.81MB (Test)	❌ Crashes (OOM)	✅ 3.5s	∞x improvement

Test Project Success:

📊 Processing large object with 125,709 items
🌊 Streaming JSON parsing: 473.998ms
✅ Found 125,709 objects  
💾 Final memory: 2498MB (managed, no crash)
🚀 Root object inflation: 283.785ms
✅ Optimized parsing successful

🔧 API Usage

Automatic optimization (recommended):

const project = XcodeProject.openLazy(path, {
  skipFullInflation: true,
  progressCallback: (message) => console.log(message)
});

Manual strategy selection:

const result = parseOptimized(contents, {
  progressCallback: (processed, total, stage) => { ... }
});

🎯 Parsing Strategy Selection

• <5MB: Original JsonVisitor (fastest for small files)
• 5-50MB: OptimizedJsonVisitor (eliminates object spread bottlenecks)
• >50MB: StreamingJsonVisitor (chunked processing, memory management)

✅ Breaking Changes

None - all optimizations are backward compatible. Existing XcodeProject.open() continues to work unchanged.

🧪 Testing

• ✅ All existing tests pass
• ✅ Successfully handles Test project (125K+ objects)
• ✅ Performance improvements verified on small, medium, and large projects
• ✅ Memory usage optimized across all file sizes

This enables parsing of previously impossible large Xcode projects while significantly improving performance for all project sizes! 🎉