webpack/lib/errors/DuplicateModulesWarning.js

Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Alexander Akait @alexander-akait
*/

"use strict";

const formatSize = require("../util/formatSize");
const WebpackError = require("./WebpackError");

/**
 * @typedef {object} DuplicateModuleDetails
 * @property {string} name
 * @property {number} chunks how many chunks carry a copy
 * @property {string[]} entrypoints the entrypoints those chunks belong to, when more than one
 * @property {number} wasted bytes the extra copies cost
 */

class DuplicateModulesWarning extends WebpackError {
	/**
	 * Creates an instance of DuplicateModulesWarning.
	 * @param {DuplicateModuleDetails[]} modules the worst offenders, largest waste first
	 * @param {number} wasted bytes all duplicated copies cost together
	 */
	constructor(modules, wasted) {
		const list = modules
			.map((module) => {
				// Which entrypoints pay for it is the actionable part, so it leads
				// where the copies are spread across more than one.
				const where =
					module.entrypoints.length > 1
						? `in ${module.entrypoints.join(", ")}, ${module.chunks} chunks`
						: `in ${module.chunks} chunks`;

				return `\n  ${module.name} (${where}, ${formatSize(module.wasted)} extra)`;
			})
			.join("");

		super(
			`duplicate modules: copies of the same module across chunks add ${formatSize(
				wasted
			)}:${list}\nA module reached from several chunks is emitted into each of them unless a shared chunk holds it. 'optimization.splitChunks' can pull it into one, with 'chunks: "all"' where the copies are in different entrypoints.\nFor more info visit https://webpack.js.org/plugins/split-chunks-plugin/`
		);

		/** @type {string} */
		this.name = "DuplicateModulesWarning";
	}
}

module.exports = DuplicateModulesWarning;