A high-performance AST-based structural diff tool for JavaScript that intelligently matches renamed functions and variables in minified or obfuscated code.

astdiff analyzes JavaScript files at the Abstract Syntax Tree (AST) level to identify structural changes between versions, even when functions and variables have been renamed. Unlike traditional text-based diffs, it understands code structure and can match semantically equivalent code blocks.

• Intelligent Matching: Uses MinHash signatures and structural fingerprinting to match renamed functions
• Minified Code Support: Designed to work with heavily minified/obfuscated JavaScript
• Fast Performance: Parallel processing and optimized algorithms handle large files efficiently
• Multiple Output Formats: Summary, detailed, compact, side-by-side, and JSON outputs
• Source Map Support: Can utilize source maps to show original names when available
• Comprehensive Dumps: Save and reload analysis results for faster repeated comparisons

cargo install --path .

Or build from source:

cargo build --release
./target/release/astdiff --help

Compare two JavaScript files:

astdiff file1.js file2.js

Choose different output styles with --format:

# Summary view (default)
astdiff old.js new.js

# Detailed view with full function bodies
astdiff old.js new.js --format detailed

# Compact view (just locations)
astdiff old.js new.js --format compact

# Side-by-side comparison
astdiff old.js new.js --format side-by-side

# JSON output for programmatic use
astdiff old.js new.js --format json

# Use source maps for better names
astdiff old.js new.js --map1 old.js.map --map2 new.js.map

# Show renamed functions (hidden by default)
ASTDIFF_SHOW_RENAMES=1 astdiff old.js new.js

# Save analysis for faster re-runs
astdiff old.js new.js --dump analysis.astdump

# Generate detailed matching report
astdiff old.js new.js --report-path report.html

Save analysis results for faster repeated comparisons:

# Create a comprehensive dump
astdiff v1.js v2.js --dump comparison.astdump

# Query the dump
astdiff query comparison.astdump find functionName
astdiff query comparison.astdump summary
astdiff query comparison.astdump validate

# Load and display the dump
astdiff load comparison.astdump

# Canonicalize JavaScript (normalize variable names)
astdiff canonicalize input.js

# Inspect a specific declaration
astdiff inspect file.js functionName
astdiff inspect file.js functionName --compare-file other.js

# Apply source map to canonicalized code
astdiff apply-mapping canonical.js mapping.json

1. Parsing: Uses tree-sitter to parse JavaScript into ASTs
2. Declaration Extraction: Identifies all functions, variables, classes, imports, and exports
3. Structural Hashing: Creates hash signatures for each declaration's AST structure
4. MinHash Signatures: Generates compact signatures for efficient similarity estimation
5. Fingerprinting: Extracts semantic features (strings, constants, API calls) for better matching
6. Parallel Matching: Uses parallel algorithms to find best matches between declarations
7. Change Detection: Identifies additions, deletions, modifications, and renames

Optimized for large minified files:

• Processes files with 7,500+ declarations in ~20 seconds
• Parallel extraction and matching algorithms
• Efficient u64-based structural hashing
• MinHash filtering reduces comparison complexity from O(n²) to manageable levels

The tool reports several types of changes:

• Added/Removed Functions: New or deleted declarations
• Modified Functions: Structurally changed but matched declarations
• Renamed Functions: High-confidence matches with different names (hidden by default)
• Structural Similarity: Overall percentage of matched declarations

Example output:

Structural similarity: 98.5%
Matched declarations: 7483/7490 vs 7501
Changes: 18 additions, 7 deletions, 10 modifications (+ 7206 renames)

• ASTDIFF_SHOW_RENAMES: Show renamed functions in output
• ASTDIFF_DEBUG: Enable debug output for fingerprint extraction
• ASTDIFF_PROFILE: Show performance profiling information

Requirements:

• Rust 1.70+
• C++ compiler (for tree-sitter)

git clone https://github.com/yourusername/astdiff
cd astdiff
cargo build --release

MIT License - see LICENSE file for details