webpack/lib/optimize/MinChunkSizePlugin.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 Tobias Koppers @sokra
*/

"use strict";

const { STAGE_ADVANCED } = require("./OptimizationStages");

/** @import Chunk from "../graph/Chunk" */
/** @import Compiler from "../Compiler" */

/**
 * @schema plugins/optimize/MinChunkSizePlugin
 * @typedef {object} MinChunkSizePluginOptions
 * @property {number=} chunkOverhead Constant overhead for a chunk.
 * @property {number=} entryChunkMultiplicator Multiplicator for initial chunks.
 * @property {number} minChunkSize Minimum number of characters.
 */

const PLUGIN_NAME = "MinChunkSizePlugin";

class MinChunkSizePlugin {
	/**
	 * Creates an instance of MinChunkSizePlugin.
	 * @param {MinChunkSizePluginOptions} options options object
	 */
	constructor(options) {
		/** @type {MinChunkSizePluginOptions} */
		this.options = options;
	}

	/**
	 * Applies the plugin by registering its hooks on the compiler.
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		compiler.hooks.validate.tap(PLUGIN_NAME, () => {
			compiler.validate(
				() => require("../../schemas/plugins/optimize/MinChunkSizePlugin.json"),
				this.options,
				{
					name: "Min Chunk Size Plugin",
					baseDataPath: "options"
				},
				(options) =>
					require("../../schemas/plugins/optimize/MinChunkSizePlugin.check")(
						options
					)
			);
		});
		compiler.hooks.compilation.tap(PLUGIN_NAME, (compilation) => {
			compilation.hooks.optimizeChunks.tap(
				{
					name: PLUGIN_NAME,
					stage: STAGE_ADVANCED
				},
				(chunks) => {
					const chunkGraph = compilation.chunkGraph;
					const equalOptions = {
						chunkOverhead: 1,
						entryChunkMultiplicator: 1
					};

					/** @type {Map<Chunk, number>} */
					const chunkSizesMap = new Map();
					/** @type {[Chunk, Chunk][]} */
					const combinations = [];
					/** @type {Chunk[]} */
					const smallChunks = [];
					/** @type {Chunk[]} */
					const visitedChunks = [];
					for (const a of chunks) {
						// check if one of the chunks sizes is smaller than the minChunkSize
						// and filter pairs that can NOT be integrated!
						if (
							chunkGraph.getChunkSize(a, equalOptions) <
							this.options.minChunkSize
						) {
							smallChunks.push(a);
							for (const b of visitedChunks) {
								if (chunkGraph.canChunksBeIntegrated(b, a)) {
									combinations.push([b, a]);
								}
							}
						} else {
							for (const b of smallChunks) {
								if (chunkGraph.canChunksBeIntegrated(b, a)) {
									combinations.push([b, a]);
								}
							}
						}
						chunkSizesMap.set(a, chunkGraph.getChunkSize(a, this.options));
						visitedChunks.push(a);
					}

					const sortedSizeFilteredExtendedPairCombinations = combinations
						.map((pair) => {
							// extend combination pairs with size and integrated size
							const a = /** @type {number} */ (chunkSizesMap.get(pair[0]));
							const b = /** @type {number} */ (chunkSizesMap.get(pair[1]));
							const ab = chunkGraph.getIntegratedChunksSize(
								pair[0],
								pair[1],
								this.options
							);
							/** @type {[number, number, Chunk, Chunk]} */
							const extendedPair = [a + b - ab, ab, pair[0], pair[1]];
							return extendedPair;
						})
						.sort((a, b) => {
							// sadly javascript does an in place 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];

					chunkGraph.integrateChunks(pair[2], pair[3]);
					compilation.chunks.delete(pair[3]);
					return true;
				}
			);
		});
	}
}

module.exports = MinChunkSizePlugin;