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 { validate } = require("schema-utils");
const schema = require("../../schemas/plugins/optimize/MinChunkSizePlugin.json");
const { STAGE_ADVANCED } = require("../OptimizationStages");

/** @typedef {import("../Chunk")} Chunk */
/** @typedef {import("../Compiler")} Compiler */

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

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

	/**
	 * Apply the plugin
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		const options = this.options;
		const minChunkSize = options.minChunkSize;
		compiler.hooks.compilation.tap("MinChunkSizePlugin", compilation => {
			compilation.hooks.optimizeChunks.tap(
				{
					name: "MinChunkSizePlugin",
					stage: STAGE_ADVANCED
				},
				chunks => {
					const chunkGraph = compilation.chunkGraph;
					const equalOptions = {
						chunkOverhead: 1,
						entryChunkMultiplicator: 1
					};

					const chunkSizesMap = new Map();
					/** @type {[Chunk, Chunk][]} */
					const combinations = [];
					/** @type {Chunk[]} */
					const smallChunks = [];
					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) < 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, options));
						visitedChunks.push(a);
					}

					const sortedSizeFilteredExtendedPairCombinations = combinations
						.map(pair => {
							// extend combination pairs with size and integrated size
							const a = chunkSizesMap.get(pair[0]);
							const b = chunkSizesMap.get(pair[1]);
							const ab = chunkGraph.getIntegratedChunksSize(
								pair[0],
								pair[1],
								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;