webpack/lib/optimize/RemoveParentModulesPlugin.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 { STAGE_BASIC } = require("../OptimizationStages");
const Queue = require("../util/Queue");
const { intersect } = require("../util/SetHelpers");

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

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

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

				while (queue.length > 0) {
					const chunkGroup = queue.dequeue();
					let availableModules = availableModulesMap.get(chunkGroup);
					let changed = false;
					for (const parent of chunkGroup.parentsIterable) {
						const availableModulesInParent = availableModulesMap.get(parent);
						if (availableModulesInParent !== undefined) {
							// If we know the available modules in parent: process these
							if (availableModules === undefined) {
								// if we have not own info yet: create new entry
								availableModules = new Set(availableModulesInParent);
								for (const chunk of parent.chunks) {
									for (const m of chunkGraph.getChunkModulesIterable(chunk)) {
										availableModules.add(m);
									}
								}
								availableModulesMap.set(chunkGroup, availableModules);
								changed = true;
							} else {
								for (const m of availableModules) {
									if (
										!chunkGraph.isModuleInChunkGroup(m, parent) &&
										!availableModulesInParent.has(m)
									) {
										availableModules.delete(m);
										changed = true;
									}
								}
							}
						}
					}
					if (changed) {
						// if something changed: enqueue our children
						for (const child of chunkGroup.childrenIterable) {
							queue.enqueue(child);
						}
					}
				}

				// now we have available modules for every chunk
				for (const chunk of chunks) {
					const availableModulesSets = Array.from(
						chunk.groupsIterable,
						chunkGroup => availableModulesMap.get(chunkGroup)
					);
					if (availableModulesSets.some(s => s === undefined)) continue; // No info about this chunk group
					const availableModules =
						availableModulesSets.length === 1
							? availableModulesSets[0]
							: intersect(availableModulesSets);
					const numberOfModules = chunkGraph.getNumberOfChunkModules(chunk);
					const toRemove = new Set();
					if (numberOfModules < availableModules.size) {
						for (const m of chunkGraph.getChunkModulesIterable(chunk)) {
							if (availableModules.has(m)) {
								toRemove.add(m);
							}
						}
					} else {
						for (const m of availableModules) {
							if (chunkGraph.isModuleInChunk(m, chunk)) {
								toRemove.add(m);
							}
						}
					}
					for (const module of toRemove) {
						chunkGraph.disconnectChunkAndModule(chunk, module);
					}
				}
			};
			compilation.hooks.optimizeChunks.tap(
				{
					name: "RemoveParentModulesPlugin",
					stage: STAGE_BASIC
				},
				handler
			);
		});
	}
}
module.exports = RemoveParentModulesPlugin;