webpack/lib/optimize/MinChunkSizePlugin.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support 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 Tobias Koppers @sokra
*/
"use strict";

const validateOptions = require("schema-utils");
const schema = require("../../schemas/plugins/optimize/MinChunkSizePlugin.json");

/** @typedef {import("../../declarations/plugins/optimize/MinChunkSizePlugin").MinChunkSizePluginOptions} MinChunkSizePluginOptions */

class MinChunkSizePlugin {
	/**
	 * @param {MinChunkSizePluginOptions} options options object
	 */
	constructor(options) {
		validateOptions(schema, options, "Min Chunk Size Plugin");
		this.options = options;
	}

	apply(compiler) {
		const options = this.options;
		const minChunkSize = options.minChunkSize;
		compiler.hooks.compilation.tap("MinChunkSizePlugin", compilation => {
			compilation.hooks.optimizeChunksAdvanced.tap(
				"MinChunkSizePlugin",
				chunks => {
					const equalOptions = {
						chunkOverhead: 1,
						entryChunkMultiplicator: 1
					};

					const sortedSizeFilteredExtendedPairCombinations = chunks
						.reduce((combinations, a, idx) => {
							// create combination pairs
							for (let i = 0; i < idx; i++) {
								const b = chunks[i];
								combinations.push([b, a]);
							}
							return combinations;
						}, [])
						.filter(pair => {
							// check if one of the chunks sizes is smaller than the minChunkSize
							const p0SmallerThanMinChunkSize =
								pair[0].size(equalOptions) < minChunkSize;
							const p1SmallerThanMinChunkSize =
								pair[1].size(equalOptions) < minChunkSize;
							return p0SmallerThanMinChunkSize || p1SmallerThanMinChunkSize;
						})
						.map(pair => {
							// extend combination pairs with size and integrated size
							const a = pair[0].size(options);
							const b = pair[1].size(options);
							const ab = pair[0].integratedSize(pair[1], options);
							return [a + b - ab, ab, pair[0], pair[1]];
						})
						.filter(pair => {
							// filter pairs that do not have an integratedSize
							// meaning they can NOT be integrated!
							return pair[1] !== false;
						})
						.sort((a, b) => {
							// sadly javascript does an inplace sort here
							// sort by size
							const diff = b[0] - a[0];
							if (diff !== 0) return diff;
							return a[1] - b[1];
						});

					if (sortedSizeFilteredExtendedPairCombinations.length === 0) return;

					const pair = sortedSizeFilteredExtendedPairCombinations[0];

					pair[2].integrate(pair[3], "min-size");
					chunks.splice(chunks.indexOf(pair[3]), 1);
					return true;
				}
			);
		});
	}
}
module.exports = MinChunkSizePlugin;