webpack/lib/optimize/FlagIncludedChunksPlugin.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 { compareIds } = require("../util/comparators");

/** @import Chunk, { ChunkId } from "../graph/Chunk" */
/** @import Compiler from "../Compiler" */
/** @import Module from "../module/Module" */

const PLUGIN_NAME = "FlagIncludedChunksPlugin";

class FlagIncludedChunksPlugin {
	/**
	 * Applies the plugin by registering its hooks on the compiler.
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		compiler.hooks.compilation.tap(PLUGIN_NAME, (compilation) => {
			compilation.hooks.optimizeChunkIds.tap(PLUGIN_NAME, (chunks) => {
				const chunkGraph = compilation.chunkGraph;

				// Two bit integers per module, within v8's 2^31 SMI range. The bits are
				// spread so 2^31 falls to about one module in `modulesCount` and 2^0 to
				// any module missing a better one, which gives the modulo below.
				/** @type {WeakMap<Module, number>} */
				const moduleBits = new WeakMap();
				const modulesCount = compilation.modules.size;

				// precalculate the modulo values for each bit
				const modulo = 1 / (1 / modulesCount) ** (1 / 31);
				/** @type {number[]} */
				const modulos = Array.from(
					{ length: 31 },
					/**
					 * Handles the callback logic for this hook.
					 * @param {number} x x
					 * @param {number} i i
					 * @returns {number} result
					 */
					(x, i) => (modulo ** i) | 0
				);

				// iterate all modules to generate bit values
				let i = 0;
				for (const module of compilation.modules) {
					let bit = 30;
					while (i % modulos[bit] !== 0) {
						bit--;
					}
					moduleBits.set(module, 1 << bit);
					i++;
				}

				// iterate all chunks to generate bitmaps
				/** @type {WeakMap<Chunk, number>} */
				const chunkModulesHash = new WeakMap();
				for (const chunk of chunks) {
					let hash = 0;
					for (const module of chunkGraph.getChunkModulesIterable(chunk)) {
						hash |= /** @type {number} */ (moduleBits.get(module));
					}
					chunkModulesHash.set(chunk, hash);
				}

				// Chunks that received an included id and need their `ids` re-sorted
				// once, after all pushes — instead of re-sorting on every push
				// inside the nested loop below (https://github.com/webpack/webpack/issues/18837).
				/** @type {Set<Chunk>} */
				const chunksWithIncludedIds = new Set();

				for (const chunkA of chunks) {
					const chunkAHash =
						/** @type {number} */
						(chunkModulesHash.get(chunkA));
					const chunkAModulesCount = chunkGraph.getNumberOfChunkModules(chunkA);
					if (chunkAModulesCount === 0) continue;
					/** @type {undefined | Module} */
					let bestModule;
					for (const module of chunkGraph.getChunkModulesIterable(chunkA)) {
						if (
							bestModule === undefined ||
							chunkGraph.getNumberOfModuleChunks(bestModule) >
								chunkGraph.getNumberOfModuleChunks(module)
						) {
							bestModule = module;
						}
					}
					loopB: for (const chunkB of chunkGraph.getModuleChunksIterable(
						/** @type {Module} */ (bestModule)
					)) {
						// as we iterate the same iterables twice
						// skip if we find ourselves
						if (chunkA === chunkB) continue;

						const chunkBModulesCount =
							chunkGraph.getNumberOfChunkModules(chunkB);

						// ids for empty chunks are not included
						if (chunkBModulesCount === 0) continue;

						// instead of swapping A and B just bail
						// as we loop twice the current A will be B and B then A
						if (chunkAModulesCount > chunkBModulesCount) continue;

						// is chunkA in chunkB?

						// we do a cheap check for the hash value
						const chunkBHash =
							/** @type {number} */
							(chunkModulesHash.get(chunkB));
						if ((chunkBHash & chunkAHash) !== chunkAHash) continue;

						// compare all modules
						for (const m of chunkGraph.getChunkModulesIterable(chunkA)) {
							if (!chunkGraph.isModuleInChunk(m, chunkB)) continue loopB;
						}

						/** @type {ChunkId[]} */
						(chunkB.ids).push(/** @type {ChunkId} */ (chunkA.id));
						chunksWithIncludedIds.add(chunkB);
					}
				}

				// Sort each affected chunk's ids once (https://github.com/webpack/webpack/issues/18837).
				for (const chunk of chunksWithIncludedIds) {
					/** @type {ChunkId[]} */
					(chunk.ids).sort(compareIds);
				}
			});
		});
	}
}

module.exports = FlagIncludedChunksPlugin;