duplicate-package-checker-webpack-plugin

Webpack plugin that warns you when multiple versions of the same package exist in a build.

Why?

It might be possible that a single package gets included multiple times in a Webpack build due to different package versions. This situation may happen without any warning, resulting in extra bloat in your build and may lead to hard-to-find bugs.

This plugin will warn you of such cases to minimize build size and avoid bugs caused by unintended duplicate packages.

Motivation: https://github.com/webpack/webpack/issues/385 and https://github.com/webpack/webpack/issues/646.

Install

npm install duplicate-package-checker-webpack-plugin --save-dev

Configuration

Add the plugin to your webpack config:

var DuplicatePackageCheckerPlugin = require('duplicate-package-checker-webpack-plugin');

module.exports = {
    plugins: [
      new DuplicatePackageCheckerPlugin()
    ]
};

You can also pass an object with configurable options:

new DuplicatePackageCheckerPlugin({
  // Also show module that is requiring each duplicate package
  verbose: true,
  // Emit errors instead of warnings
  emitError: true,
  /**
   * Exclude instances of packages from the results.
   * If all instances of a package are excluded, or all instances except one,
   * then the package is no longer considered duplicated and won't be emitted as a warning/error.
   * @param {Object} instance
   * @param {string} instance.name The name of the package
   * @param {string} instance.version The version of the package
   * @param {string} instance.path Absolute path to the package
   * @param {?string} instance.issuer Absolute path to the module that requested the package
   * @returns {boolean} true to exclude the instance, false otherwise
   */
  exclude(instance) {
    return instance.name === 'fbjs';
  }
})