package.lib.optimize.RemoveParentModulesPlugin.js Maven / Gradle / Ivy

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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.
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/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/

"use strict";

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

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

/**
 * Intersects multiple masks represented as bigints
 * @param {bigint[]} masks The module masks to intersect
 * @returns {bigint} The intersection of all masks
 */
function intersectMasks(masks) {
	let result = masks[0];
	for (let i = masks.length - 1; i >= 1; i--) {
		result &= masks[i];
	}
	return result;
}

const ZERO_BIGINT = BigInt(0);
const ONE_BIGINT = BigInt(1);
const THIRTY_TWO_BIGINT = BigInt(32);

/**
 * Parses the module mask and returns the modules represented by it
 * @param {bigint} mask the module mask
 * @param {Module[]} ordinalModules the modules in the order they were added to the mask (LSB is index 0)
 * @returns {Generator} the modules represented by the mask
 */
function* getModulesFromMask(mask, ordinalModules) {
	let offset = 31;
	while (mask !== ZERO_BIGINT) {
		// Consider the last 32 bits, since that's what Math.clz32 can handle
		let last32 = Number(BigInt.asUintN(32, mask));
		while (last32 > 0) {
			let last = Math.clz32(last32);
			// The number of trailing zeros is the number trimmed off the input mask + 31 - the number of leading zeros
			// The 32 is baked into the initial value of offset
			const moduleIndex = offset - last;
			// The number of trailing zeros is the index into the array generated by getOrCreateModuleMask
			const module = ordinalModules[moduleIndex];
			yield module;
			// Remove the matched module from the mask
			// Since we can only count leading zeros, not trailing, we can't just downshift the mask
			last32 &= ~(1 << (31 - last));
		}

		// Remove the processed chunk from the mask
		mask >>= THIRTY_TWO_BIGINT;
		offset += 32;
	}
}

class RemoveParentModulesPlugin {
	/**
	 * @param {Compiler} compiler the compiler
	 * @returns {void}
	 */
	apply(compiler) {
		compiler.hooks.compilation.tap("RemoveParentModulesPlugin", compilation => {
			/**
			 * @param {Iterable} chunks the chunks
			 * @param {ChunkGroup[]} chunkGroups the chunk groups
			 */
			const handler = (chunks, chunkGroups) => {
				const chunkGraph = compilation.chunkGraph;
				const queue = new Set();
				const availableModulesMap = new WeakMap();

				let nextModuleMask = ONE_BIGINT;
				const maskByModule = new WeakMap();
				/** @type {Module[]} */
				const ordinalModules = [];

				/**
				 * Gets or creates a unique mask for a module
				 * @param {Module} mod the module to get the mask for
				 * @returns {bigint} the module mask to uniquely identify the module
				 */
				const getOrCreateModuleMask = mod => {
					let id = maskByModule.get(mod);
					if (id === undefined) {
						id = nextModuleMask;
						ordinalModules.push(mod);
						maskByModule.set(mod, id);
						nextModuleMask <<= ONE_BIGINT;
					}
					return id;
				};

				// Initialize masks by chunk and by chunk group for quicker comparisons
				const chunkMasks = new WeakMap();
				for (const chunk of chunks) {
					let mask = ZERO_BIGINT;
					for (const m of chunkGraph.getChunkModulesIterable(chunk)) {
						const id = getOrCreateModuleMask(m);
						mask |= id;
					}
					chunkMasks.set(chunk, mask);
				}

				const chunkGroupMasks = new WeakMap();
				for (const chunkGroup of chunkGroups) {
					let mask = ZERO_BIGINT;
					for (const chunk of chunkGroup.chunks) {
						const chunkMask = chunkMasks.get(chunk);
						if (chunkMask !== undefined) {
							mask |= chunkMask;
						}
					}
					chunkGroupMasks.set(chunkGroup, mask);
				}

				for (const chunkGroup of compilation.entrypoints.values()) {
					// initialize available modules for chunks without parents
					availableModulesMap.set(chunkGroup, ZERO_BIGINT);
					for (const child of chunkGroup.childrenIterable) {
						queue.add(child);
					}
				}
				for (const chunkGroup of compilation.asyncEntrypoints) {
					// initialize available modules for chunks without parents
					availableModulesMap.set(chunkGroup, ZERO_BIGINT);
					for (const child of chunkGroup.childrenIterable) {
						queue.add(child);
					}
				}

				for (const chunkGroup of queue) {
					let availableModulesMask = availableModulesMap.get(chunkGroup);
					let changed = false;
					for (const parent of chunkGroup.parentsIterable) {
						const availableModulesInParent = availableModulesMap.get(parent);
						if (availableModulesInParent !== undefined) {
							const parentMask =
								availableModulesInParent | chunkGroupMasks.get(parent);
							// If we know the available modules in parent: process these
							if (availableModulesMask === undefined) {
								// if we have not own info yet: create new entry
								availableModulesMask = parentMask;
								changed = true;
							} else {
								let newMask = availableModulesMask & parentMask;
								if (newMask !== availableModulesMask) {
									changed = true;
									availableModulesMask = newMask;
								}
							}
						}
					}

					if (changed) {
						availableModulesMap.set(chunkGroup, availableModulesMask);
						// if something changed: enqueue our children
						for (const child of chunkGroup.childrenIterable) {
							// Push the child to the end of the queue
							queue.delete(child);
							queue.add(child);
						}
					}
				}

				// now we have available modules for every chunk
				for (const chunk of chunks) {
					const chunkMask = chunkMasks.get(chunk);
					if (chunkMask === undefined) continue; // No info about this chunk

					const availableModulesSets = Array.from(
						chunk.groupsIterable,
						chunkGroup => availableModulesMap.get(chunkGroup)
					);
					if (availableModulesSets.some(s => s === undefined)) continue; // No info about this chunk group

					const availableModulesMask = intersectMasks(availableModulesSets);
					const toRemoveMask = chunkMask & availableModulesMask;
					if (toRemoveMask !== ZERO_BIGINT) {
						for (const module of getModulesFromMask(
							toRemoveMask,
							ordinalModules
						)) {
							chunkGraph.disconnectChunkAndModule(chunk, module);
						}
					}
				}
			};
			compilation.hooks.optimizeChunks.tap(
				{
					name: "RemoveParentModulesPlugin",
					stage: STAGE_BASIC
				},
				handler
			);
		});
	}
}
module.exports = RemoveParentModulesPlugin;