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node_modules/webpack/lib/optimize/RemoveParentModulesPlugin.js

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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");
+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;