Reliable Module IDs Plugin

This Webpack 4 plugin provides more reliable module IDs for improved long-term caching and code reuse between project installations and builds. It is intended to bridge the gap until we can use the deterministic IDs feature in Webpack 5.

Installation

This is a Node.js module available through the npm registry. Node 8 and Webpack 4.38 or higher are required.

Installation is done using the npm install command:

$ npm install --save-dev reliable-module-ids-plugin

Once installed the plugin can be added to your Webpack plugins configuration:

const ReliableModuleIdsPlugin = require('reliable-module-ids-plugin')

module.exports = {
  //...
  plugins: [
    new ReliableModuleIdsPlugin({
      // options
    })
  ]
}

If you have already configured optimization.moduleIds you should set this to false so Webpack will defer to the provided algorithm.

Options

`hashFunction`

The hashing algorithm to use, defaults to 'md5'. All functions from Node.JS' crypto.createHash are supported.

`hashDigest`

The encoding to use when generating the hash, defaults to 'hex'. All encodings from Node.JS' hash.digest are supported.

`hashDigestLength`

The prefix length of the hash digest to use, defaults to 8. Note that some generated IDs might be longer than specified here, to avoid module ID collisions.

Motivation

Module IDs play an important part in Webpack's content hashing algorithm. For the assets we compile with Webpack to be long-term cacheable and consistent over time we need to ensure the module ID algorithm is deterministic. By default Webpack will use numerical module IDs when run in production mode but because these IDs are assigned incrementally in the order that modules are added to the dependency graph these will naturally change over time. Webpack already provides alternatives for this; named which is the module's path relative to the project root and hashed which is a hash of this path, however if you use npm then these module paths are not deterministic and can change over time and between environments.

Prior Art

This plugin is based upon Webpack's built-in HashedModuleIdsPlugin by Tobias Koppers and uses the node_modules path normalization as demonstrated in the SimpleNamedModulesPlugin by Tomer Brisker.