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App Module Path

App Module Path is a simple Node.js utility that enables adding additional directories to the Node.js module search path for top-level application modules. This allows application-level modules to be required as if they were installed into the node_modules directory, while maintaining proper isolation to prevent installed modules from accessing application code.

Package Information

Package Name: app-module-path
Package Type: npm
Language: JavaScript
Installation: npm install app-module-path --save

Core Imports

const { addPath, removePath, enableForDir } = require('app-module-path');

For automatic path registration:

// Auto-registers the directory containing the requiring module
require('app-module-path/register');

// Auto-registers the current working directory  
require('app-module-path/cwd');

ES6 imports:

import { addPath, removePath, enableForDir } from 'app-module-path';

// Auto-registration patterns
import 'app-module-path/register';
import 'app-module-path/cwd';

Basic Usage

// IMPORTANT: Add this to the very beginning of your main script
require('app-module-path').addPath(__dirname);

// Now you can require modules from your application directory structure
// as if they were installed in node_modules
const myModule = require('src/my-module');
const anotherModule = require('lib/utils/helper');

Alternative automatic registration:

// Automatically adds the directory containing this file to the search path
require('app-module-path/register');

// Or automatically adds the current working directory
require('app-module-path/cwd');

Architecture

App Module Path works by overriding Node.js's built-in Module._nodeModulePaths method to extend the module resolution system:

Path Management: Maintains an internal list of additional search paths that are appended to Node's default module resolution
Security Model: Only allows application-level modules to access the extended paths; installed modules in node_modules are restricted from accessing application code
Hierarchy Support: Automatically updates parent module paths when new search paths are added
Explicit Enablement: Provides mechanism to explicitly allow specific directories within node_modules to use extended paths

Capabilities

Path Management

Add and remove directories from the Node.js module search path.

/**
 * Adds a directory path to the Node module search path
 * @param {string} path - The directory path to add to the module search path
 * @param {Module} [parent] - The parent module context (defaults to module.parent)
 */
function addPath(path, parent);

/**
 * Removes a directory path from the Node module search path
 * @param {string} path - The directory path to remove from the module search path
 */
function removePath(path);

Usage Examples:

const { addPath, removePath } = require('app-module-path');
const path = require('path');

// Add application source directory to module path  
addPath(path.join(__dirname, 'src'));

// Add multiple directories
addPath(path.join(__dirname, 'lib'));
addPath(path.join(__dirname, 'app'));

// Remove a path when no longer needed
removePath(path.join(__dirname, 'src'));

Directory Enablement

Explicitly enable app-module-path functionality for specific directories, including those within node_modules.

/**
 * Explicitly enables app-module-path functionality for a specific directory
 * @param {string} dir - The directory path to enable for app-module-path resolution
 */
function enableForDir(dir);

Usage Example:

const { enableForDir } = require('app-module-path');
const path = require('path');

// Allow a specific installed package to access application modules
const packageDir = path.dirname(require.resolve('some-installed-package'));
enableForDir(packageDir);

Automatic Registration

Convenience entry points that automatically register paths without explicit function calls.

register.js Entry Point:

// Automatically calls addPath(dirname(module.parent.filename), module.parent)
require('app-module-path/register');

Equivalent to:

const { addPath } = require('app-module-path');
const path = require('path');
addPath(path.dirname(__filename));

cwd.js Entry Point:

// Automatically calls addPath(process.cwd())
require('app-module-path/cwd');