generate-package-json-webpack-plugin

For limiting the dependencies inside package.json to only those that are actually being used by your code.

Why generate a new package.json?

This plugin is useful for when you have a large source project for development / testing from which smaller Node.js projects are bundled for various deployments and applications. Such as Google Cloud Functions.

Or even just for bundling your regular Node.js server code, and knowing that your package.json is as lean as it can possibly be for that next deployment.

We all know how our development environments can get a bit messy... 😅

💾 Install

npm install generate-package-json-webpack-plugin --save-dev

🔌 Usage

const basePackageValues = {
  "name": "my-nodejs-module",
  "version": "1.0.0",
  "main": "./index.js",
  "engines": {
    "node": "<= 6.9.1"
  }
}

const versionsPackageFilename = __dirname + "/package.json";

// inside your webpack configuration
plugins: [new GeneratePackageJsonPlugin(basePackageValues, versionsPackageFilename)],

That's pretty much it. The plugin will generate a new package.json file with all the dependencies your code uses, merged with the values you pass into the plugin. The versions for the detected dependencies are sourced from the versionsPackageFilename here.

Important note on externals

The plugin only writes the dependencies of modules which are found in the input code and have been marked in externals inside of your Webpack config.

This is logical because if a module is not marked as an external module it is included in your final webpack bundle and hence wouldn't need to be installed as a dependency again on deployment.

Because of this, this plugin is best used in conjunction with something like webpack-node-externals, which you can use to make sure your node modules are not included with your final bundle.js, like so:

const nodeExternals = require("webpack-node-externals");

// inside your webpack config
externals: [nodeExternals({
    whitelist: [/^module-I-want-bundled/],
})],

As you can see, you can add modules that you deliberately do want bundled using the whitelist option.

Adding modules outside of your code (build modules etc.)

OR to deliberately set different versions of bundled dependencies

Simply place those dependencies inside the basePackageValues object which represents the base of the new package.json to be created.

Keep the version number string empty ("") to pull the version from your original package.json which was set with versionsPackageFilename. To use a version which is different - set the version string deliberately here.

const basePackageValues = {
  "name": "my-nodejs-module",
  "version": "1.0.0",
  "main": "./index.js",
  "scripts": {
    "start": "cross-var node --max-old-space-size=$NODE_JS_MAX_OLD_SPACE_SIZE ./server.js"
  }
  "engines": {
    "node": "<= 6.9.1"
  },
  dependencies: {
    "cross-var": "^1.1.0",
    "cross-env": "",
  },
}

In this example, cross-var has deliberately been set to version ^1.1.0, and regardless of what is in versionsPackageFilename it will use this version. cross-env however will pull its version number from versionsPackageFilename.

This is mostly useful for adding dependencies which are required at runtime but which are not picked up in your webpack bundle. Such as cross-var in this example which injects environment variables into a run script in a cross-platform friendly way.

Simple API

new GeneratePackageJsonPlugin(basePackageValues, versionsPackageFilename, extraOptions)

First argument: basePackageValues

( Required ) You should set the base values for your package.json file here. For example:

const basePackageValues = {
  "name": "my-nodejs-module",
  "version": "1.0.0",
  "main": "./bundle.js",
  "engines": {
    "node": "<= 6.9.1"
  }
}

This will be merged with the generated "dependencies": { ... } to form the final package.json distribution file.

Second argument: versionsPackageFilename

( Required )

This is the filename from which the plugin will source the versions for the modules that appear in the final generated package.json. Usually it will just be the base package.json file in your parent directory (assuming that your development code has been using dependencies sourced from your base node_modules folder):

Commonly, this will be set like this:

const versionsPackageFilename = __dirname + "/package.json";

Third argument: extraOptions

( Optional )

An object with the following structure:

  {
     debug: true,
     extraSourcePackageFilenames: [
       join(__dirname, "../other-workspace/package.json"),
     ],
     additionalDependencies: {
       react: "^16.13.1",
     },
     useInstalledVersions: true,
  }

The options:

debug (default: false) : Enable to show some debugging information on how the plugin is finding dependencies and creating a new package.json.

extraSourcePackageFilenames : This is useful for mono-repos and projects where your dependencies in your code are not only defined in a single package.json file. If you share code between multiple projects or "workspaces" to be bundled into a final distribution project, you probably want to set this option.

additionalDependencies: A dictionary of additional dependencies (same as package.json format) to add to the generated file. This is useful if you have some dependencies that are not imported in you code but you still want to include them.

useInstalledVersions (default: false) : Resolve node modules and use the exact version that installed in your environment. This is useful to lock versions on production deployments.

🔍 Things to take note of

You should remember to set the "main": "./index.js" to the correct filename (would probably be the output bundle file from the same webpack task), and / or correctly set your starting script which will be run on Node.js server deployments by npm start. You can set these values in the basePackageValues object you pass into the plugin, example:

const basePackageValues = {
  "name": "my-nodejs-module",
  "version": "1.0.0",
  "main": "./bundle.js",
  "scripts": {
    "start": "node ./bundle.js"
  },
  "engines": {
    "node": "<= 6.9.1"
  }
}