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YANG Tools Reference

Complete reference for YANG validation and processing tools used in this project.

Core Tools

pyang

Primary YANG validator, converter, and code generator.

Installation

pip install pyang

Common Usage

# Validate YANG model
pyang --strict model.yang

# Generate tree view
pyang -f tree model.yang

# Generate documentation
pyang -f html model.yang

# Multiple output formats
pyang -f jstree model.yang    # JSON tree
pyang -f yin model.yang       # YIN format

Key Options

  • --strict: Enable strict validation
  • --path PATH: Add directories to module search path
  • -f FORMAT: Output format (tree, html, jstree, yin, etc.)
  • --help: Show all available options

libyang (Optional)

C library providing yanglint tools and Python bindings.

Installation

macOS: 

brew install libyang
pip install libyang  # Python bindings

Ubuntu/Debian: 

sudo apt install libyang-dev libyang-tools
pip install libyang  # Python bindings

Usage

# Validate with yanglint
yanglint model.yang

# Validate data against model
yanglint -s model.yang data.json

Project Scripts

Main Validation Scripts

Script Purpose Options
validate-bgp.sh Validate all BGP models All options supported
validate-nokia-bgp.sh Nokia BGP validation All options supported
validate-openconfig-bgp.sh OpenConfig BGP validation All options supported

Script Options Reference

Option Long Form Description Example
-h --help Show help message ./validate-bgp.sh -h
-t --tree Show tree structure ./validate-bgp.sh -t
-e --errors Show detailed errors ./validate-bgp.sh -e
-l NUM --lines NUM Tree lines to show ./validate-bgp.sh -t -l 50
-q --quiet Minimal output ./validate-bgp.sh -q
-a --all All checks (tree + errors) ./validate-bgp.sh -a

Setup Scripts

Script Purpose Usage
scripts/setup-dev-env.sh Setup Python environment ./scripts/setup-dev-env.sh
scripts/setup-bgp-models.sh Create model symlinks ./scripts/setup-bgp-models.sh

Advanced Usage

Custom Validation

# Validate with custom search paths
pyang --strict --path types:common:ietf model.yang

# Validate multiple models
pyang --strict *.yang

# Generate trees for documentation
pyang -f tree --tree-line-length 80 model.yang

Error Analysis

# Show detailed errors
pyang --strict --verbose model.yang

# Check specific warnings
pyang --strict --lint model.yang

# Validate imports only
pyang --strict --check-import-modules model.yang

Output Formats

# Tree formats
pyang -f tree model.yang              # ASCII tree
pyang -f jstree model.yang            # JSON tree

# Documentation formats  
pyang -f html model.yang              # HTML documentation
pyang -f html --html-no-path model.yang  # Clean HTML

# Code generation
pyang -f yang model.yang              # Canonical YANG
pyang -f yin model.yang               # YIN XML format

Environment Management

Virtual Environment

# Create environment
python -m venv venv

# Activate (always required)
source venv/bin/activate  # macOS/Linux
venv\Scripts\activate     # Windows

# Install dependencies
pip install -r requirements-dev.txt

# Deactivate when done
deactivate

Search Paths

YANG models often depend on other modules. Use search paths to help pyang find dependencies:

# Single path
pyang --path types model.yang

# Multiple paths
pyang --path types:common:ietf model.yang

# Relative paths from model directory
pyang --path ../types:../common model.yang

Troubleshooting

Common Issues

"module not found in search path" 

# Add missing directories to path
pyang --path types:common:vendor-specific model.yang

"circular dependency" 

# This usually indicates a fundamental model architecture issue
# Try validating submodules individually

"pyang command not found" 

# Ensure virtual environment is activated
source venv/bin/activate

Debug Options

# Verbose output
pyang --verbose model.yang

# Show import tree
pyang --print-all-imports model.yang

# Lint checks
pyang --lint model.yang

Integration with IDEs

VS Code

Install the YANG extension for syntax highlighting and basic validation: - Search for "YANG" in extensions - Provides syntax highlighting and basic error detection

Vim/Neovim

Add YANG syntax highlighting: 

" Add to .vimrc
autocmd BufRead,BufNewFile *.yang set filetype=yang

Next Steps