duplicate-package-checker-webpack-plugin

What is duplicate-package-checker-webpack-plugin?

The duplicate-package-checker-webpack-plugin is a Webpack plugin that helps identify and eliminate duplicate packages in your Webpack bundle. This can help reduce bundle size and avoid potential issues caused by multiple versions of the same package.

What are duplicate-package-checker-webpack-plugin's main functionalities?

Basic Usage

This code demonstrates the basic usage of the plugin. By adding the DuplicatePackageCheckerPlugin to the plugins array in your Webpack configuration, it will automatically check for duplicate packages in your bundle.

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

module.exports = {
  // other webpack configuration
  plugins: [
    new DuplicatePackageCheckerPlugin(),
  ],
};

Emit Errors for Duplicates

This code sample shows how to configure the plugin to emit errors when duplicates are found. This can be useful for CI/CD pipelines to ensure that no duplicate packages are introduced.

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

module.exports = {
  // other webpack configuration
  plugins: [
    new DuplicatePackageCheckerPlugin({
      emitError: true,
    }),
  ],
};

Verbose Output

This code demonstrates how to enable verbose output, which provides more detailed information about the duplicates found in your bundle.

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

module.exports = {
  // other webpack configuration
  plugins: [
    new DuplicatePackageCheckerPlugin({
      verbose: true,
    }),
  ],
};

Other packages similar to duplicate-package-checker-webpack-plugin

inspectpack

inspectpack is a tool that provides detailed inspection of your Webpack bundle. It can help identify duplicate packages, large modules, and other potential issues. Compared to duplicate-package-checker-webpack-plugin, inspectpack offers a broader range of inspection capabilities but may require more configuration.

webpack-bundle-analyzer

webpack-bundle-analyzer is a Webpack plugin and CLI utility that represents bundle content as an interactive zoomable treemap. It helps you understand the size of your Webpack output files and can identify duplicate packages. While it provides a visual representation of your bundle, it may not be as focused on duplicates as duplicate-package-checker-webpack-plugin.

bundle-stats

bundle-stats is a Webpack plugin that generates a report of your bundle's size and composition. It can help identify duplicate packages and other inefficiencies. Compared to duplicate-package-checker-webpack-plugin, bundle-stats offers a more comprehensive analysis of your bundle's performance.

README

🕵 duplicate-package-checker-webpack-plugin

Webpack plugin that warns when your bundle contains multiple versions of the same package.

Why?

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

This plugin will warn you of such cases to minimize bundle 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 (default: false)
  verbose: true,
  // Emit errors instead of warnings (default: false)
  emitError: true,
  // Show help message if duplicate packages are found (default: true)
  showHelp: false,
  // Warn also if major versions differ (default: true)
  strict: false,
  /**
   * 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";
  }
});

Strict mode

Strict mode warns when multiple packages with different major versions (such as v1.0.0 vs v2.0.0) exist in the bundle.

Packages with different major versions introduce backward incompatible changes and require either interventions on third-party packages or unsafe workarounds (such as resolving differing package major versions dependencies with a single version).

It is suggested that strict mode is kept enabled since this improves visibility into your bundle and can help in solving and identifying potential issues.

Resolving duplicate packages in your bundle

There are multiple ways you can go about resolving duplicate packages in your bundle, the right solution mostly depends on what tools you're using and on each particular case.

Webpack resolve.alias

Add an entry in resolve.alias which will configure Webpack to route any package references to a single specified path.

For example, if Lodash is duplicated in your bundle, the following configuration would render all Lodash imports to always refer to the Lodash instance found at ./node_modules/lodash.

alias: {
  lodash: path.resolve(__dirname, 'node_modules/lodash'),
}

Note: Aliasing packages with different major versions may break your app. Use only if you're sure that all required versions are compatible, at least in the context of your app

Yarn install --flat

Yarn allows flat installations (yarn install --flat) which will only allow one version of each package to be installed.

Yarn resolutions

If you want more control over your overridden dependency versions and don't feel like using yarn install --flat, yarn supports "selective version resolution" which allows you to enforce specific versions for each dependency.

package.json

{
  "dependencies": {
    "lodash": "4.17.0",
    "old-package-with-old-lodash": "*"
  },
  "resolutions": {
    "old-package-with-old-lodash/lodash": "4.17.0"
  }
}

NPM Dedupe

If you use NPM and not Yarn, you can try running npm dedupe. NPM may leave multiple versions of the same package installed even if a single version satisfies each semver of all of its dependants.

Bump your dependencies

If your project is using an old version of a package and a dependency is using a newer version of that package, consider upgrading your project to use the newer version.

File issues!

If your project has a dependency and it's using an outdated version of a package, file an issue and notify the author to update the dependencies. Let's help keep our projects green and our applications secure, performant and bug-free!

Webpack versions

Webpack 3.x

npm install duplicate-package-checker-webpack-plugin@^2.1.0 --save-dev

Webpack 4.x

npm install duplicate-package-checker-webpack-plugin