ANVS - Automatic Node Version Switcher

Automatic Node Version Switcher is written in Rust, with a loving tip-of-the-hat to avn

ANVS is a Rust-based tool that automatically switches your Node.js version when you cd into a directory with a .nvmrc, .node-version, or package.json file. It automatically returns to your default version when you leave.

Features

• 🚀 Fast: <100ms activation time (2-3x faster than avn)
• 🔌 Compatible: Works with nvm, fnm, and n
• 🔄 Smart: Automatically returns to default version when leaving projects
• 🤖 Auto-install: Prompts to install missing versions
• ⚙️ Configurable: Customize behavior via ~/.anvsrc
• 🔒 Safe: Written in Rust with checksum verification
• 📦 Easy: Install via npm, no manual binary downloads

Quick Start

Initialize anvs with auto-detection (recommended):

# Install
npm install -g anvs

# Quick setup with auto-detection (default, < 30 seconds)
anvs init

Or use advanced mode for full customization:

anvs init --advanced

The wizard detects your shell and Node.js version manager, then guides you through setup.

Setup Modes

Quick Mode (default):

• Auto-detects shell and version managers
• Shows summary and asks for confirmation
• Completes in < 30 seconds
• Recommended for most users

Advanced Mode (--advanced):

• Step-by-step customization
• Full control over all settings
• Takes 1-2 minutes
• For users with specific requirements

Installation

anvs is installed to a central directory (~/.anvs) to ensure it's always available, regardless of the active Node.js version.

Option 1: npm (Recommended for Linux and macOS)

# Step 1: Install the package
npm install -g anvs

# Step 2: Set up your shell
anvs init

Option 2: Homebrew (macOS only)

# Step 1: Tap the repository
brew tap olvrcc/anvs

# Step 2: Install anvs
brew install anvs

# Step 3: Set up your shell
anvs init

Option 3: Cargo (Build from source)

# Install from source
cargo install --git https://github.com/olvrcc/anvs

# Set up your shell
anvs init

Complete the Installation

After installation via any method, restart your shell or run:

source ~/.bashrc  # or ~/.zshrc

Upgrading

npm:

npm update -g anvs

Note for nvm users: Global packages are Node version-specific in nvm. If you installed anvs while on Node v20 but later switched to Node v22, the global package only exists in v20. To uninstall completely, switch back to the Node version where anvs was installed before running npm uninstall -g anvs.

Homebrew:

brew upgrade anvs

Cargo:

cargo install --git https://github.com/olvrcc/anvs --force

Migration from XVN

If you're upgrading from xvn to anvs, see the Migration Guide.

Quick migration:

xvn uninstall
npm install -g anvs
anvs init

For detailed instructions, troubleshooting, and configuration migration, see docs/XVN_TO_ANVS_MIGRATION.md.

Usage

Just cd into a directory with a version file:

cd ~/my-project  # anvs automatically switches Node.js version
cd ..            # anvs switches back to your default Node.js version

Automatic Default Version

When you leave a project directory (one with a .nvmrc or other version file), anvs automatically switches back to your default Node.js version. This ensures you're always on your preferred version when not in a project.

For nvm users:

• anvs uses your default alias: nvm alias default 20.11.0
• Check your default: nvm version default

For fnm users:

• anvs uses fnm's default version
• Check your default: fnm default

Configuration:

# In ~/.anvsrc
use_default: true  # (default: true)

Disable this behavior if you prefer manual version switching:

anvs set use-default  # Interactive toggle

Supported Version Files

anvs supports multiple version file formats:

• .nvmrc - Standard nvm format with exact version or alias

  18.20.0
  

• .node-version - Alternative format, same as .nvmrc

  20.11.0
  

• package.json - npm standard with semver ranges

  {
    "engines": {
      "node": ">=18.0.0"
    }
  }

  Supports semver ranges: ^20.0.0, ~18.20.0, >=18 <21, 18.x

Manual Activation

anvs activate  # Activate version for current directory

Check Status

anvs status  # Show current configuration and activation timing

Configuration

Create ~/.anvsrc:

# Version managers (in priority order)
plugins:
  - nvm
  - fnm

# Auto-install missing versions
auto_install: prompt  # or 'always' or 'never'

# Automatically switch to default version when leaving projects
use_default: true  # or 'false' to disable

# Silent mode (no output)
silent: false

# Version file priority (first match wins)
version_files:
  - .nvmrc
  - .node-version
  - package.json  # optional, supports semver ranges

Project-level configuration (.anvs.yaml in project root):

# Override global settings for this project
auto_install: always
silent: true

Supported Version Managers

• ✅ nvm (Node Version Manager)
• ✅ fnm (Fast Node Manager)
• ⏳ n (planned for future release)
• ⏳ asdf (planned for future release)

Requirements

• Node.js 14+
• nvm or fnm installed
• bash or zsh shell
• Linux or macOS (x64 or arm64)
• Windows support planned for future release

Uninstalling

To completely remove anvs and clean up all configuration:

anvs uninstall

This command will:

• Detect all anvs installations (npm, Homebrew, Cargo)
• Remove ~/.anvs directory
• Remove ~/.anvsrc configuration
• Remove shell integration from .bashrc/.zshrc
• Provide instructions for uninstalling external packages

Use --force to skip the confirmation prompt:

anvs uninstall --force

Troubleshooting

anvs: command not found

This can happen after installation if your shell hasn't been restarted. Make sure you have run anvs init and restarted your shell.

Verify that ~/.anvs/bin is in your PATH:

echo $PATH

Verify the anvs binary is in the right place:

which anvs
# Should output: /Users/your-name/.anvs/bin/anvs

Shell hook not triggering

Make sure you ran anvs init and restarted your shell.

Verify the hook was added to your profile:

grep anvs ~/.bashrc  # or ~/.zshrc

Version not switching

Check that your version manager is installed:

nvm --version  # or fnm --version

Check that anvs detects your version file:

anvs status

Setup Issues

Shell not detected:

anvs init --shell zsh  # or bash

Version manager not detected:

• Ensure nvm or fnm is installed and in PATH
• Use advanced mode to specify manually

Permission denied:

• Check write permissions for ~/.anvsrc and shell config files
• Run with sudo if necessary (not recommended)

Debug mode

Enable debug output to see what anvs is doing:

ANVS_DEBUG=1 cd my-project

How It Works

anvs is installed to ~/.anvs/bin and this directory is added to your shell's PATH. It integrates with your shell using the chpwd hook (bash/zsh) and communicates with the parent shell via file descriptor 3 (FD:3).

When you cd into a directory:

1. Shell hook triggers on directory change.
2. anvs searches for version files (.nvmrc, etc.).
3. anvs queries configured version managers (nvm, fnm) for the version.
4. If the version is missing, anvs prompts to install it.
5. An activation command is generated and written to FD:3.
6. The parent shell executes the command, changing the Node.js version.

This approach ensures anvs can modify the parent shell environment safely.

Development

# Clone the repository
git clone https://github.com/olvrcc/anvs.git
cd anvs

# Build
cargo build

# Run tests
cargo test

# Install locally for development
cargo install --path .
anvs init

Contributing

Contributions are welcome! Please see CONTRIBUTING.md for guidelines.

Architecture

For detailed architecture documentation, see docs/ARCHITECTURE.md.

License

MIT - see LICENSE for details.

Acknowledgements

Inspired by avn by Whitney Young. anvs reimagines the concept in Rust for improved performance and reliability.