Files
LEANN/docs/ast_chunking_guide.md
Gabriel Dehan 13bb561aad Add AST-aware code chunking for better code understanding (#58)
* feat(core): Add AST-aware code chunking with astchunk integration

This PR introduces intelligent code chunking that preserves semantic boundaries
(functions, classes, methods) for better code understanding in RAG applications.

Key Features:
- AST-aware chunking for Python, Java, C#, TypeScript files
- Graceful fallback to traditional chunking for unsupported languages
- New specialized code RAG application for repositories
- Enhanced CLI with --use-ast-chunking flag
- Comprehensive test suite with integration tests

Technical Implementation:
- New chunking_utils.py module with enhanced chunking logic
- Extended base RAG framework with AST chunking arguments
- Updated document RAG with --enable-code-chunking flag
- CLI integration with proper error handling and fallback

Benefits:
- Better semantic understanding of code structure
- Improved search quality for code-related queries
- Maintains backward compatibility with existing workflows
- Supports mixed content (code + documentation) seamlessly

Dependencies:
- Added astchunk and tree-sitter parsers to pyproject.toml
- All dependencies are optional - fallback works without them

Testing:
- Comprehensive test suite in test_astchunk_integration.py
- Integration tests with document RAG
- Error handling and edge case coverage

Documentation:
- Updated README.md with AST chunking highlights
- Added ASTCHUNK_INTEGRATION.md with complete guide
- Updated features.md with new capabilities

* Refactored chunk utils

* Remove useless import

* Update README.md

* Update apps/chunking/utils.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update apps/code_rag.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Fix issue

* apply suggestion from @Copilot

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Fixes after pr review

* Fix tests not passing

* Fix linter error for documentation files

* Update .gitignore with unwanted files

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Andy Lee <andylizf@outlook.com>
2025-08-19 23:35:31 -07:00

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3.2 KiB
Markdown

# AST-Aware Code chunking guide
## Overview
This guide covers best practices for using AST-aware code chunking in LEANN. AST chunking provides better semantic understanding of code structure compared to traditional text-based chunking.
## Quick Start
### Basic Usage
```bash
# Enable AST chunking for mixed content (code + docs)
python -m apps.document_rag --enable-code-chunking --data-dir ./my_project
# Specialized code repository indexing
python -m apps.code_rag --repo-dir ./my_codebase
# Global CLI with AST support
leann build my-code-index --docs ./src --use-ast-chunking
```
### Installation
```bash
# Install LEANN with AST chunking support
uv pip install -e "."
```
## Best Practices
### When to Use AST Chunking
**Recommended for:**
- Code repositories with multiple languages
- Mixed documentation and code content
- Complex codebases with deep function/class hierarchies
- When working with Claude Code for code assistance
**Not recommended for:**
- Pure text documents
- Very large files (>1MB)
- Languages not supported by tree-sitter
### Optimal Configuration
```bash
# Recommended settings for most codebases
python -m apps.code_rag \
--repo-dir ./src \
--ast-chunk-size 768 \
--ast-chunk-overlap 96 \
--exclude-dirs .git __pycache__ node_modules build dist
```
### Supported Languages
| Extension | Language | Status |
|-----------|----------|--------|
| `.py` | Python | ✅ Full support |
| `.java` | Java | ✅ Full support |
| `.cs` | C# | ✅ Full support |
| `.ts`, `.tsx` | TypeScript | ✅ Full support |
| `.js`, `.jsx` | JavaScript | ✅ Via TypeScript parser |
## Integration Examples
### Document RAG with Code Support
```python
# Enable code chunking in document RAG
python -m apps.document_rag \
--enable-code-chunking \
--data-dir ./project \
--query "How does authentication work in the codebase?"
```
### Claude Code Integration
When using with Claude Code MCP server, AST chunking provides better context for:
- Code completion and suggestions
- Bug analysis and debugging
- Architecture understanding
- Refactoring assistance
## Troubleshooting
### Common Issues
1. **Fallback to Traditional Chunking**
- Normal behavior for unsupported languages
- Check logs for specific language support
2. **Performance with Large Files**
- Adjust `--max-file-size` parameter
- Use `--exclude-dirs` to skip unnecessary directories
3. **Quality Issues**
- Try different `--ast-chunk-size` values (512, 768, 1024)
- Adjust overlap for better context preservation
### Debug Mode
```bash
export LEANN_LOG_LEVEL=DEBUG
python -m apps.code_rag --repo-dir ./my_code
```
## Migration from Traditional Chunking
Existing workflows continue to work without changes. To enable AST chunking:
```bash
# Before
python -m apps.document_rag --chunk-size 256
# After (maintains traditional chunking for non-code files)
python -m apps.document_rag --enable-code-chunking --chunk-size 256 --ast-chunk-size 768
```
## References
- [astchunk GitHub Repository](https://github.com/yilinjz/astchunk)
- [LEANN MCP Integration](../packages/leann-mcp/README.md)
- [Research Paper](https://arxiv.org/html/2506.15655v1)
---
**Note**: AST chunking maintains full backward compatibility while enhancing code understanding capabilities.