webpack/lib/buildChunkGraph.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 AsyncDependencyToInitialChunkError = require("./AsyncDependencyToInitialChunkError");
const { connectChunkGroupParentAndChild } = require("./GraphHelpers");
const ModuleGraphConnection = require("./ModuleGraphConnection");
const { getEntryRuntime, mergeRuntime } = require("./util/runtime");

/** @typedef {import("./AsyncDependenciesBlock")} AsyncDependenciesBlock */
/** @typedef {import("./Chunk")} Chunk */
/** @typedef {import("./ChunkGroup")} ChunkGroup */
/** @typedef {import("./Compilation")} Compilation */
/** @typedef {import("./DependenciesBlock")} DependenciesBlock */
/** @typedef {import("./Dependency")} Dependency */
/** @typedef {import("./Entrypoint")} Entrypoint */
/** @typedef {import("./Module")} Module */
/** @typedef {import("./ModuleGraph")} ModuleGraph */
/** @typedef {import("./ModuleGraphConnection").ConnectionState} ConnectionState */
/** @typedef {import("./logging/Logger").Logger} Logger */
/** @typedef {import("./util/runtime").RuntimeSpec} RuntimeSpec */

/**
 * @typedef {Object} QueueItem
 * @property {number} action
 * @property {DependenciesBlock} block
 * @property {Module} module
 * @property {Chunk} chunk
 * @property {ChunkGroup} chunkGroup
 * @property {ChunkGroupInfo} chunkGroupInfo
 */

/** @typedef {Set<Module> & { plus: Set<Module> }} ModuleSetPlus */

/**
 * @typedef {Object} ChunkGroupInfo
 * @property {ChunkGroup} chunkGroup the chunk group
 * @property {RuntimeSpec} runtime the runtimes
 * @property {ModuleSetPlus} minAvailableModules current minimal set of modules available at this point
 * @property {boolean} minAvailableModulesOwned true, if minAvailableModules is owned and can be modified
 * @property {ModuleSetPlus[]} availableModulesToBeMerged enqueued updates to the minimal set of available modules
 * @property {Set<Module>=} skippedItems modules that were skipped because module is already available in parent chunks (need to reconsider when minAvailableModules is shrinking)
 * @property {Set<[Module, ConnectionState]>=} skippedModuleConnections referenced modules that where skipped because they were not active in this runtime
 * @property {ModuleSetPlus} resultingAvailableModules set of modules available including modules from this chunk group
 * @property {Set<ChunkGroupInfo>} children set of children chunk groups, that will be revisited when availableModules shrink
 * @property {Set<ChunkGroupInfo>} availableSources set of chunk groups that are the source for minAvailableModules
 * @property {Set<ChunkGroupInfo>} availableChildren set of chunk groups which depend on the this chunk group as availableSource
 * @property {number} preOrderIndex next pre order index
 * @property {number} postOrderIndex next post order index
 */

/**
 * @typedef {Object} BlockChunkGroupConnection
 * @property {ChunkGroupInfo} originChunkGroupInfo origin chunk group
 * @property {ChunkGroup} chunkGroup referenced chunk group
 */

const EMPTY_SET = /** @type {ModuleSetPlus} */ (new Set());
EMPTY_SET.plus = EMPTY_SET;

/**
 * @param {ModuleSetPlus} a first set
 * @param {ModuleSetPlus} b second set
 * @returns {number} cmp
 */
const bySetSize = (a, b) => {
	return b.size + b.plus.size - a.size - a.plus.size;
};

const extractBlockModules = (module, moduleGraph, runtime, blockModulesMap) => {
	let blockCache;
	let modules;

	const arrays = [];

	const queue = [module];
	while (queue.length > 0) {
		const block = queue.pop();
		const arr = [];
		arrays.push(arr);
		blockModulesMap.set(block, arr);
		for (const b of block.blocks) {
			queue.push(b);
		}
	}

	for (const connection of moduleGraph.getOutgoingConnections(module)) {
		const d = connection.dependency;
		// We skip connections without dependency
		if (!d) continue;
		const m = connection.module;
		// We skip connections without Module pointer
		if (!m) continue;
		// We skip weak connections
		if (connection.weak) continue;
		const state = connection.getActiveState(runtime);
		// We skip inactive connections
		if (state === false) continue;

		const block = moduleGraph.getParentBlock(d);
		let index = moduleGraph.getParentBlockIndex(d);

		// deprecated fallback
		if (index < 0) {
			index = block.dependencies.indexOf(d);
		}

		if (blockCache !== block) {
			modules = blockModulesMap.get((blockCache = block));
		}

		const i = index << 2;
		modules[i] = m;
		modules[i + 1] = state;
	}

	for (const modules of arrays) {
		if (modules.length === 0) continue;
		let indexMap;
		let length = 0;
		outer: for (let j = 0; j < modules.length; j += 2) {
			const m = modules[j];
			if (m === undefined) continue;
			const state = modules[j + 1];
			if (indexMap === undefined) {
				let i = 0;
				for (; i < length; i += 2) {
					if (modules[i] === m) {
						const merged = modules[i + 1];
						if (merged === true) continue outer;
						modules[i + 1] = ModuleGraphConnection.addConnectionStates(
							merged,
							state
						);
					}
				}
				modules[length] = m;
				length++;
				modules[length] = state;
				length++;
				if (length > 30) {
					// To avoid worse case performance, we will use an index map for
					// linear cost access, which allows to maintain O(n) complexity
					// while keeping allocations down to a minimum
					indexMap = new Map();
					for (let i = 0; i < length; i += 2) {
						indexMap.set(modules[i], i + 1);
					}
				}
			} else {
				const idx = indexMap.get(m);
				if (idx !== undefined) {
					const merged = modules[idx];
					if (merged === true) continue outer;
					modules[idx] = ModuleGraphConnection.addConnectionStates(
						merged,
						state
					);
				} else {
					modules[length] = m;
					length++;
					modules[length] = state;
					indexMap.set(m, length);
					length++;
				}
			}
		}
		modules.length = length;
	}
};

/**
 *
 * @param {Logger} logger a logger
 * @param {Compilation} compilation the compilation
 * @param {Map<Entrypoint, Module[]>} inputEntrypointsAndModules chunk groups which are processed with the modules
 * @param {Map<ChunkGroup, ChunkGroupInfo>} chunkGroupInfoMap mapping from chunk group to available modules
 * @param {Map<AsyncDependenciesBlock, BlockChunkGroupConnection[]>} blockConnections connection for blocks
 * @param {Set<DependenciesBlock>} blocksWithNestedBlocks flag for blocks that have nested blocks
 * @param {Set<ChunkGroup>} allCreatedChunkGroups filled with all chunk groups that are created here
 */
const visitModules = (
	logger,
	compilation,
	inputEntrypointsAndModules,
	chunkGroupInfoMap,
	blockConnections,
	blocksWithNestedBlocks,
	allCreatedChunkGroups
) => {
	const { moduleGraph, chunkGraph, moduleMemCaches } = compilation;

	const blockModulesRuntimeMap = new Map();

	/** @type {RuntimeSpec | false} */
	let blockModulesMapRuntime = false;
	let blockModulesMap;

	/**
	 *
	 * @param {DependenciesBlock} block block
	 * @param {RuntimeSpec} runtime runtime
	 * @returns {(Module | ConnectionState)[]} block modules in flatten tuples
	 */
	const getBlockModules = (block, runtime) => {
		if (blockModulesMapRuntime !== runtime) {
			blockModulesMap = blockModulesRuntimeMap.get(runtime);
			if (blockModulesMap === undefined) {
				blockModulesMap = new Map();
				blockModulesRuntimeMap.set(runtime, blockModulesMap);
			}
		}
		let blockModules = blockModulesMap.get(block);
		if (blockModules !== undefined) return blockModules;
		const module = /** @type {Module} */ (block.getRootBlock());
		const memCache = moduleMemCaches && moduleMemCaches.get(module);
		if (memCache !== undefined) {
			const map = memCache.provide(
				"bundleChunkGraph.blockModules",
				runtime,
				() => {
					logger.time("visitModules: prepare");
					const map = new Map();
					extractBlockModules(module, moduleGraph, runtime, map);
					logger.timeAggregate("visitModules: prepare");
					return map;
				}
			);
			for (const [block, blockModules] of map)
				blockModulesMap.set(block, blockModules);
			return map.get(block);
		} else {
			logger.time("visitModules: prepare");
			extractBlockModules(module, moduleGraph, runtime, blockModulesMap);
			blockModules = blockModulesMap.get(block);
			logger.timeAggregate("visitModules: prepare");
			return blockModules;
		}
	};

	let statProcessedQueueItems = 0;
	let statProcessedBlocks = 0;
	let statConnectedChunkGroups = 0;
	let statProcessedChunkGroupsForMerging = 0;
	let statMergedAvailableModuleSets = 0;
	let statForkedAvailableModules = 0;
	let statForkedAvailableModulesCount = 0;
	let statForkedAvailableModulesCountPlus = 0;
	let statForkedMergedModulesCount = 0;
	let statForkedMergedModulesCountPlus = 0;
	let statForkedResultModulesCount = 0;
	let statChunkGroupInfoUpdated = 0;
	let statChildChunkGroupsReconnected = 0;

	let nextChunkGroupIndex = 0;
	let nextFreeModulePreOrderIndex = 0;
	let nextFreeModulePostOrderIndex = 0;

	/** @type {Map<DependenciesBlock, ChunkGroupInfo>} */
	const blockChunkGroups = new Map();

	/** @type {Map<string, ChunkGroupInfo>} */
	const namedChunkGroups = new Map();

	/** @type {Map<string, ChunkGroupInfo>} */
	const namedAsyncEntrypoints = new Map();

	const ADD_AND_ENTER_ENTRY_MODULE = 0;
	const ADD_AND_ENTER_MODULE = 1;
	const ENTER_MODULE = 2;
	const PROCESS_BLOCK = 3;
	const PROCESS_ENTRY_BLOCK = 4;
	const LEAVE_MODULE = 5;

	/** @type {QueueItem[]} */
	let queue = [];

	/** @type {Map<ChunkGroupInfo, Set<ChunkGroupInfo>>} */
	const queueConnect = new Map();
	/** @type {Set<ChunkGroupInfo>} */
	const chunkGroupsForCombining = new Set();

	// Fill queue with entrypoint modules
	// Create ChunkGroupInfo for entrypoints
	for (const [chunkGroup, modules] of inputEntrypointsAndModules) {
		const runtime = getEntryRuntime(
			compilation,
			chunkGroup.name,
			chunkGroup.options
		);
		/** @type {ChunkGroupInfo} */
		const chunkGroupInfo = {
			chunkGroup,
			runtime,
			minAvailableModules: undefined,
			minAvailableModulesOwned: false,
			availableModulesToBeMerged: [],
			skippedItems: undefined,
			resultingAvailableModules: undefined,
			children: undefined,
			availableSources: undefined,
			availableChildren: undefined,
			preOrderIndex: 0,
			postOrderIndex: 0
		};
		chunkGroup.index = nextChunkGroupIndex++;
		if (chunkGroup.getNumberOfParents() > 0) {
			// minAvailableModules for child entrypoints are unknown yet, set to undefined.
			// This means no module is added until other sets are merged into
			// this minAvailableModules (by the parent entrypoints)
			const skippedItems = new Set();
			for (const module of modules) {
				skippedItems.add(module);
			}
			chunkGroupInfo.skippedItems = skippedItems;
			chunkGroupsForCombining.add(chunkGroupInfo);
		} else {
			// The application may start here: We start with an empty list of available modules
			chunkGroupInfo.minAvailableModules = EMPTY_SET;
			const chunk = chunkGroup.getEntrypointChunk();
			for (const module of modules) {
				queue.push({
					action: ADD_AND_ENTER_MODULE,
					block: module,
					module,
					chunk,
					chunkGroup,
					chunkGroupInfo
				});
			}
		}
		chunkGroupInfoMap.set(chunkGroup, chunkGroupInfo);
		if (chunkGroup.name) {
			namedChunkGroups.set(chunkGroup.name, chunkGroupInfo);
		}
	}
	// Fill availableSources with parent-child dependencies between entrypoints
	for (const chunkGroupInfo of chunkGroupsForCombining) {
		const { chunkGroup } = chunkGroupInfo;
		chunkGroupInfo.availableSources = new Set();
		for (const parent of chunkGroup.parentsIterable) {
			const parentChunkGroupInfo = chunkGroupInfoMap.get(parent);
			chunkGroupInfo.availableSources.add(parentChunkGroupInfo);
			if (parentChunkGroupInfo.availableChildren === undefined) {
				parentChunkGroupInfo.availableChildren = new Set();
			}
			parentChunkGroupInfo.availableChildren.add(chunkGroupInfo);
		}
	}
	// pop() is used to read from the queue
	// so it need to be reversed to be iterated in
	// correct order
	queue.reverse();

	/** @type {Set<ChunkGroupInfo>} */
	const outdatedChunkGroupInfo = new Set();
	/** @type {Set<ChunkGroupInfo>} */
	const chunkGroupsForMerging = new Set();
	/** @type {QueueItem[]} */
	let queueDelayed = [];

	/** @type {[Module, ConnectionState][]} */
	const skipConnectionBuffer = [];
	/** @type {Module[]} */
	const skipBuffer = [];
	/** @type {QueueItem[]} */
	const queueBuffer = [];

	/** @type {Module} */
	let module;
	/** @type {Chunk} */
	let chunk;
	/** @type {ChunkGroup} */
	let chunkGroup;
	/** @type {DependenciesBlock} */
	let block;
	/** @type {ChunkGroupInfo} */
	let chunkGroupInfo;

	// For each async Block in graph
	/**
	 * @param {AsyncDependenciesBlock} b iterating over each Async DepBlock
	 * @returns {void}
	 */
	const iteratorBlock = b => {
		// 1. We create a chunk group with single chunk in it for this Block
		// but only once (blockChunkGroups map)
		let cgi = blockChunkGroups.get(b);
		/** @type {ChunkGroup} */
		let c;
		/** @type {Entrypoint} */
		let entrypoint;
		const entryOptions = b.groupOptions && b.groupOptions.entryOptions;
		if (cgi === undefined) {
			const chunkName = (b.groupOptions && b.groupOptions.name) || b.chunkName;
			if (entryOptions) {
				cgi = namedAsyncEntrypoints.get(chunkName);
				if (!cgi) {
					entrypoint = compilation.addAsyncEntrypoint(
						entryOptions,
						module,
						b.loc,
						b.request
					);
					entrypoint.index = nextChunkGroupIndex++;
					cgi = {
						chunkGroup: entrypoint,
						runtime: entrypoint.options.runtime || entrypoint.name,
						minAvailableModules: EMPTY_SET,
						minAvailableModulesOwned: false,
						availableModulesToBeMerged: [],
						skippedItems: undefined,
						resultingAvailableModules: undefined,
						children: undefined,
						availableSources: undefined,
						availableChildren: undefined,
						preOrderIndex: 0,
						postOrderIndex: 0
					};
					chunkGroupInfoMap.set(entrypoint, cgi);

					chunkGraph.connectBlockAndChunkGroup(b, entrypoint);
					if (chunkName) {
						namedAsyncEntrypoints.set(chunkName, cgi);
					}
				} else {
					entrypoint = /** @type {Entrypoint} */ (cgi.chunkGroup);
					// TODO merge entryOptions
					entrypoint.addOrigin(module, b.loc, b.request);
					chunkGraph.connectBlockAndChunkGroup(b, entrypoint);
				}

				// 2. We enqueue the DependenciesBlock for traversal
				queueDelayed.push({
					action: PROCESS_ENTRY_BLOCK,
					block: b,
					module: module,
					chunk: entrypoint.chunks[0],
					chunkGroup: entrypoint,
					chunkGroupInfo: cgi
				});
			} else {
				cgi = namedChunkGroups.get(chunkName);
				if (!cgi) {
					c = compilation.addChunkInGroup(
						b.groupOptions || b.chunkName,
						module,
						b.loc,
						b.request
					);
					c.index = nextChunkGroupIndex++;
					cgi = {
						chunkGroup: c,
						runtime: chunkGroupInfo.runtime,
						minAvailableModules: undefined,
						minAvailableModulesOwned: undefined,
						availableModulesToBeMerged: [],
						skippedItems: undefined,
						resultingAvailableModules: undefined,
						children: undefined,
						availableSources: undefined,
						availableChildren: undefined,
						preOrderIndex: 0,
						postOrderIndex: 0
					};
					allCreatedChunkGroups.add(c);
					chunkGroupInfoMap.set(c, cgi);
					if (chunkName) {
						namedChunkGroups.set(chunkName, cgi);
					}
				} else {
					c = cgi.chunkGroup;
					if (c.isInitial()) {
						compilation.errors.push(
							new AsyncDependencyToInitialChunkError(chunkName, module, b.loc)
						);
						c = chunkGroup;
					}
					c.addOptions(b.groupOptions);
					c.addOrigin(module, b.loc, b.request);
				}
				blockConnections.set(b, []);
			}
			blockChunkGroups.set(b, cgi);
		} else if (entryOptions) {
			entrypoint = /** @type {Entrypoint} */ (cgi.chunkGroup);
		} else {
			c = cgi.chunkGroup;
		}

		if (c !== undefined) {
			// 2. We store the connection for the block
			// to connect it later if needed
			blockConnections.get(b).push({
				originChunkGroupInfo: chunkGroupInfo,
				chunkGroup: c
			});

			// 3. We enqueue the chunk group info creation/updating
			let connectList = queueConnect.get(chunkGroupInfo);
			if (connectList === undefined) {
				connectList = new Set();
				queueConnect.set(chunkGroupInfo, connectList);
			}
			connectList.add(cgi);

			// TODO check if this really need to be done for each traversal
			// or if it is enough when it's queued when created
			// 4. We enqueue the DependenciesBlock for traversal
			queueDelayed.push({
				action: PROCESS_BLOCK,
				block: b,
				module: module,
				chunk: c.chunks[0],
				chunkGroup: c,
				chunkGroupInfo: cgi
			});
		} else {
			chunkGroupInfo.chunkGroup.addAsyncEntrypoint(entrypoint);
		}
	};

	/**
	 * @param {DependenciesBlock} block the block
	 * @returns {void}
	 */
	const processBlock = block => {
		statProcessedBlocks++;
		// get prepared block info
		const blockModules = getBlockModules(block, chunkGroupInfo.runtime);

		if (blockModules !== undefined) {
			const { minAvailableModules } = chunkGroupInfo;
			// Buffer items because order need to be reversed to get indices correct
			// Traverse all referenced modules
			for (let i = 0; i < blockModules.length; i += 2) {
				const refModule = /** @type {Module} */ (blockModules[i]);
				if (chunkGraph.isModuleInChunk(refModule, chunk)) {
					// skip early if already connected
					continue;
				}
				const activeState = /** @type {ConnectionState} */ (
					blockModules[i + 1]
				);
				if (activeState !== true) {
					skipConnectionBuffer.push([refModule, activeState]);
					if (activeState === false) continue;
				}
				if (
					activeState === true &&
					(minAvailableModules.has(refModule) ||
						minAvailableModules.plus.has(refModule))
				) {
					// already in parent chunks, skip it for now
					skipBuffer.push(refModule);
					continue;
				}
				// enqueue, then add and enter to be in the correct order
				// this is relevant with circular dependencies
				queueBuffer.push({
					action: activeState === true ? ADD_AND_ENTER_MODULE : PROCESS_BLOCK,
					block: refModule,
					module: refModule,
					chunk,
					chunkGroup,
					chunkGroupInfo
				});
			}
			// Add buffered items in reverse order
			if (skipConnectionBuffer.length > 0) {
				let { skippedModuleConnections } = chunkGroupInfo;
				if (skippedModuleConnections === undefined) {
					chunkGroupInfo.skippedModuleConnections = skippedModuleConnections =
						new Set();
				}
				for (let i = skipConnectionBuffer.length - 1; i >= 0; i--) {
					skippedModuleConnections.add(skipConnectionBuffer[i]);
				}
				skipConnectionBuffer.length = 0;
			}
			if (skipBuffer.length > 0) {
				let { skippedItems } = chunkGroupInfo;
				if (skippedItems === undefined) {
					chunkGroupInfo.skippedItems = skippedItems = new Set();
				}
				for (let i = skipBuffer.length - 1; i >= 0; i--) {
					skippedItems.add(skipBuffer[i]);
				}
				skipBuffer.length = 0;
			}
			if (queueBuffer.length > 0) {
				for (let i = queueBuffer.length - 1; i >= 0; i--) {
					queue.push(queueBuffer[i]);
				}
				queueBuffer.length = 0;
			}
		}

		// Traverse all Blocks
		for (const b of block.blocks) {
			iteratorBlock(b);
		}

		if (block.blocks.length > 0 && module !== block) {
			blocksWithNestedBlocks.add(block);
		}
	};

	/**
	 * @param {DependenciesBlock} block the block
	 * @returns {void}
	 */
	const processEntryBlock = block => {
		statProcessedBlocks++;
		// get prepared block info
		const blockModules = getBlockModules(block, chunkGroupInfo.runtime);

		if (blockModules !== undefined) {
			// Traverse all referenced modules
			for (let i = 0; i < blockModules.length; i += 2) {
				const refModule = /** @type {Module} */ (blockModules[i]);
				const activeState = /** @type {ConnectionState} */ (
					blockModules[i + 1]
				);
				// enqueue, then add and enter to be in the correct order
				// this is relevant with circular dependencies
				queueBuffer.push({
					action:
						activeState === true ? ADD_AND_ENTER_ENTRY_MODULE : PROCESS_BLOCK,
					block: refModule,
					module: refModule,
					chunk,
					chunkGroup,
					chunkGroupInfo
				});
			}
			// Add buffered items in reverse order
			if (queueBuffer.length > 0) {
				for (let i = queueBuffer.length - 1; i >= 0; i--) {
					queue.push(queueBuffer[i]);
				}
				queueBuffer.length = 0;
			}
		}

		// Traverse all Blocks
		for (const b of block.blocks) {
			iteratorBlock(b);
		}

		if (block.blocks.length > 0 && module !== block) {
			blocksWithNestedBlocks.add(block);
		}
	};

	const processQueue = () => {
		while (queue.length) {
			statProcessedQueueItems++;
			const queueItem = queue.pop();
			module = queueItem.module;
			block = queueItem.block;
			chunk = queueItem.chunk;
			chunkGroup = queueItem.chunkGroup;
			chunkGroupInfo = queueItem.chunkGroupInfo;

			switch (queueItem.action) {
				case ADD_AND_ENTER_ENTRY_MODULE:
					chunkGraph.connectChunkAndEntryModule(
						chunk,
						module,
						/** @type {Entrypoint} */ (chunkGroup)
					);
				// fallthrough
				case ADD_AND_ENTER_MODULE: {
					if (chunkGraph.isModuleInChunk(module, chunk)) {
						// already connected, skip it
						break;
					}
					// We connect Module and Chunk
					chunkGraph.connectChunkAndModule(chunk, module);
				}
				// fallthrough
				case ENTER_MODULE: {
					const index = chunkGroup.getModulePreOrderIndex(module);
					if (index === undefined) {
						chunkGroup.setModulePreOrderIndex(
							module,
							chunkGroupInfo.preOrderIndex++
						);
					}

					if (
						moduleGraph.setPreOrderIndexIfUnset(
							module,
							nextFreeModulePreOrderIndex
						)
					) {
						nextFreeModulePreOrderIndex++;
					}

					// reuse queueItem
					queueItem.action = LEAVE_MODULE;
					queue.push(queueItem);
				}
				// fallthrough
				case PROCESS_BLOCK: {
					processBlock(block);
					break;
				}
				case PROCESS_ENTRY_BLOCK: {
					processEntryBlock(block);
					break;
				}
				case LEAVE_MODULE: {
					const index = chunkGroup.getModulePostOrderIndex(module);
					if (index === undefined) {
						chunkGroup.setModulePostOrderIndex(
							module,
							chunkGroupInfo.postOrderIndex++
						);
					}

					if (
						moduleGraph.setPostOrderIndexIfUnset(
							module,
							nextFreeModulePostOrderIndex
						)
					) {
						nextFreeModulePostOrderIndex++;
					}
					break;
				}
			}
		}
	};

	const calculateResultingAvailableModules = chunkGroupInfo => {
		if (chunkGroupInfo.resultingAvailableModules)
			return chunkGroupInfo.resultingAvailableModules;

		const minAvailableModules = chunkGroupInfo.minAvailableModules;

		// Create a new Set of available modules at this point
		// We want to be as lazy as possible. There are multiple ways doing this:
		// Note that resultingAvailableModules is stored as "(a) + (b)" as it's a ModuleSetPlus
		// - resultingAvailableModules = (modules of chunk) + (minAvailableModules + minAvailableModules.plus)
		// - resultingAvailableModules = (minAvailableModules + modules of chunk) + (minAvailableModules.plus)
		// We choose one depending on the size of minAvailableModules vs minAvailableModules.plus

		let resultingAvailableModules;
		if (minAvailableModules.size > minAvailableModules.plus.size) {
			// resultingAvailableModules = (modules of chunk) + (minAvailableModules + minAvailableModules.plus)
			resultingAvailableModules =
				/** @type {Set<Module> & {plus: Set<Module>}} */ (new Set());
			for (const module of minAvailableModules.plus)
				minAvailableModules.add(module);
			minAvailableModules.plus = EMPTY_SET;
			resultingAvailableModules.plus = minAvailableModules;
			chunkGroupInfo.minAvailableModulesOwned = false;
		} else {
			// resultingAvailableModules = (minAvailableModules + modules of chunk) + (minAvailableModules.plus)
			resultingAvailableModules =
				/** @type {Set<Module> & {plus: Set<Module>}} */ (
					new Set(minAvailableModules)
				);
			resultingAvailableModules.plus = minAvailableModules.plus;
		}

		// add the modules from the chunk group to the set
		for (const chunk of chunkGroupInfo.chunkGroup.chunks) {
			for (const m of chunkGraph.getChunkModulesIterable(chunk)) {
				resultingAvailableModules.add(m);
			}
		}
		return (chunkGroupInfo.resultingAvailableModules =
			resultingAvailableModules);
	};

	const processConnectQueue = () => {
		// Figure out new parents for chunk groups
		// to get new available modules for these children
		for (const [chunkGroupInfo, targets] of queueConnect) {
			// 1. Add new targets to the list of children
			if (chunkGroupInfo.children === undefined) {
				chunkGroupInfo.children = targets;
			} else {
				for (const target of targets) {
					chunkGroupInfo.children.add(target);
				}
			}

			// 2. Calculate resulting available modules
			const resultingAvailableModules =
				calculateResultingAvailableModules(chunkGroupInfo);

			const runtime = chunkGroupInfo.runtime;

			// 3. Update chunk group info
			for (const target of targets) {
				target.availableModulesToBeMerged.push(resultingAvailableModules);
				chunkGroupsForMerging.add(target);
				const oldRuntime = target.runtime;
				const newRuntime = mergeRuntime(oldRuntime, runtime);
				if (oldRuntime !== newRuntime) {
					target.runtime = newRuntime;
					outdatedChunkGroupInfo.add(target);
				}
			}

			statConnectedChunkGroups += targets.size;
		}
		queueConnect.clear();
	};

	const processChunkGroupsForMerging = () => {
		statProcessedChunkGroupsForMerging += chunkGroupsForMerging.size;

		// Execute the merge
		for (const info of chunkGroupsForMerging) {
			const availableModulesToBeMerged = info.availableModulesToBeMerged;
			let cachedMinAvailableModules = info.minAvailableModules;

			statMergedAvailableModuleSets += availableModulesToBeMerged.length;

			// 1. Get minimal available modules
			// It doesn't make sense to traverse a chunk again with more available modules.
			// This step calculates the minimal available modules and skips traversal when
			// the list didn't shrink.
			if (availableModulesToBeMerged.length > 1) {
				availableModulesToBeMerged.sort(bySetSize);
			}
			let changed = false;
			merge: for (const availableModules of availableModulesToBeMerged) {
				if (cachedMinAvailableModules === undefined) {
					cachedMinAvailableModules = availableModules;
					info.minAvailableModules = cachedMinAvailableModules;
					info.minAvailableModulesOwned = false;
					changed = true;
				} else {
					if (info.minAvailableModulesOwned) {
						// We own it and can modify it
						if (cachedMinAvailableModules.plus === availableModules.plus) {
							for (const m of cachedMinAvailableModules) {
								if (!availableModules.has(m)) {
									cachedMinAvailableModules.delete(m);
									changed = true;
								}
							}
						} else {
							for (const m of cachedMinAvailableModules) {
								if (!availableModules.has(m) && !availableModules.plus.has(m)) {
									cachedMinAvailableModules.delete(m);
									changed = true;
								}
							}
							for (const m of cachedMinAvailableModules.plus) {
								if (!availableModules.has(m) && !availableModules.plus.has(m)) {
									// We can't remove modules from the plus part
									// so we need to merge plus into the normal part to allow modifying it
									const iterator =
										cachedMinAvailableModules.plus[Symbol.iterator]();
									// fast forward add all modules until m
									/** @type {IteratorResult<Module>} */
									let it;
									while (!(it = iterator.next()).done) {
										const module = it.value;
										if (module === m) break;
										cachedMinAvailableModules.add(module);
									}
									// check the remaining modules before adding
									while (!(it = iterator.next()).done) {
										const module = it.value;
										if (
											availableModules.has(module) ||
											availableModules.plus.has(m)
										) {
											cachedMinAvailableModules.add(module);
										}
									}
									cachedMinAvailableModules.plus = EMPTY_SET;
									changed = true;
									continue merge;
								}
							}
						}
					} else if (cachedMinAvailableModules.plus === availableModules.plus) {
						// Common and fast case when the plus part is shared
						// We only need to care about the normal part
						if (availableModules.size < cachedMinAvailableModules.size) {
							// the new availableModules is smaller so it's faster to
							// fork from the new availableModules
							statForkedAvailableModules++;
							statForkedAvailableModulesCount += availableModules.size;
							statForkedMergedModulesCount += cachedMinAvailableModules.size;
							// construct a new Set as intersection of cachedMinAvailableModules and availableModules
							const newSet = /** @type {ModuleSetPlus} */ (new Set());
							newSet.plus = availableModules.plus;
							for (const m of availableModules) {
								if (cachedMinAvailableModules.has(m)) {
									newSet.add(m);
								}
							}
							statForkedResultModulesCount += newSet.size;
							cachedMinAvailableModules = newSet;
							info.minAvailableModulesOwned = true;
							info.minAvailableModules = newSet;
							changed = true;
							continue merge;
						}
						for (const m of cachedMinAvailableModules) {
							if (!availableModules.has(m)) {
								// cachedMinAvailableModules need to be modified
								// but we don't own it
								statForkedAvailableModules++;
								statForkedAvailableModulesCount +=
									cachedMinAvailableModules.size;
								statForkedMergedModulesCount += availableModules.size;
								// construct a new Set as intersection of cachedMinAvailableModules and availableModules
								// as the plus part is equal we can just take over this one
								const newSet = /** @type {ModuleSetPlus} */ (new Set());
								newSet.plus = availableModules.plus;
								const iterator = cachedMinAvailableModules[Symbol.iterator]();
								// fast forward add all modules until m
								/** @type {IteratorResult<Module>} */
								let it;
								while (!(it = iterator.next()).done) {
									const module = it.value;
									if (module === m) break;
									newSet.add(module);
								}
								// check the remaining modules before adding
								while (!(it = iterator.next()).done) {
									const module = it.value;
									if (availableModules.has(module)) {
										newSet.add(module);
									}
								}
								statForkedResultModulesCount += newSet.size;
								cachedMinAvailableModules = newSet;
								info.minAvailableModulesOwned = true;
								info.minAvailableModules = newSet;
								changed = true;
								continue merge;
							}
						}
					} else {
						for (const m of cachedMinAvailableModules) {
							if (!availableModules.has(m) && !availableModules.plus.has(m)) {
								// cachedMinAvailableModules need to be modified
								// but we don't own it
								statForkedAvailableModules++;
								statForkedAvailableModulesCount +=
									cachedMinAvailableModules.size;
								statForkedAvailableModulesCountPlus +=
									cachedMinAvailableModules.plus.size;
								statForkedMergedModulesCount += availableModules.size;
								statForkedMergedModulesCountPlus += availableModules.plus.size;
								// construct a new Set as intersection of cachedMinAvailableModules and availableModules
								const newSet = /** @type {ModuleSetPlus} */ (new Set());
								newSet.plus = EMPTY_SET;
								const iterator = cachedMinAvailableModules[Symbol.iterator]();
								// fast forward add all modules until m
								/** @type {IteratorResult<Module>} */
								let it;
								while (!(it = iterator.next()).done) {
									const module = it.value;
									if (module === m) break;
									newSet.add(module);
								}
								// check the remaining modules before adding
								while (!(it = iterator.next()).done) {
									const module = it.value;
									if (
										availableModules.has(module) ||
										availableModules.plus.has(module)
									) {
										newSet.add(module);
									}
								}
								// also check all modules in cachedMinAvailableModules.plus
								for (const module of cachedMinAvailableModules.plus) {
									if (
										availableModules.has(module) ||
										availableModules.plus.has(module)
									) {
										newSet.add(module);
									}
								}
								statForkedResultModulesCount += newSet.size;
								cachedMinAvailableModules = newSet;
								info.minAvailableModulesOwned = true;
								info.minAvailableModules = newSet;
								changed = true;
								continue merge;
							}
						}
						for (const m of cachedMinAvailableModules.plus) {
							if (!availableModules.has(m) && !availableModules.plus.has(m)) {
								// cachedMinAvailableModules need to be modified
								// but we don't own it
								statForkedAvailableModules++;
								statForkedAvailableModulesCount +=
									cachedMinAvailableModules.size;
								statForkedAvailableModulesCountPlus +=
									cachedMinAvailableModules.plus.size;
								statForkedMergedModulesCount += availableModules.size;
								statForkedMergedModulesCountPlus += availableModules.plus.size;
								// construct a new Set as intersection of cachedMinAvailableModules and availableModules
								// we already know that all modules directly from cachedMinAvailableModules are in availableModules too
								const newSet = /** @type {ModuleSetPlus} */ (
									new Set(cachedMinAvailableModules)
								);
								newSet.plus = EMPTY_SET;
								const iterator =
									cachedMinAvailableModules.plus[Symbol.iterator]();
								// fast forward add all modules until m
								/** @type {IteratorResult<Module>} */
								let it;
								while (!(it = iterator.next()).done) {
									const module = it.value;
									if (module === m) break;
									newSet.add(module);
								}
								// check the remaining modules before adding
								while (!(it = iterator.next()).done) {
									const module = it.value;
									if (
										availableModules.has(module) ||
										availableModules.plus.has(module)
									) {
										newSet.add(module);
									}
								}
								statForkedResultModulesCount += newSet.size;
								cachedMinAvailableModules = newSet;
								info.minAvailableModulesOwned = true;
								info.minAvailableModules = newSet;
								changed = true;
								continue merge;
							}
						}
					}
				}
			}
			availableModulesToBeMerged.length = 0;
			if (changed) {
				info.resultingAvailableModules = undefined;
				outdatedChunkGroupInfo.add(info);
			}
		}
		chunkGroupsForMerging.clear();
	};

	const processChunkGroupsForCombining = () => {
		for (const info of chunkGroupsForCombining) {
			for (const source of info.availableSources) {
				if (!source.minAvailableModules) {
					chunkGroupsForCombining.delete(info);
					break;
				}
			}
		}
		for (const info of chunkGroupsForCombining) {
			const availableModules = /** @type {ModuleSetPlus} */ (new Set());
			availableModules.plus = EMPTY_SET;
			const mergeSet = set => {
				if (set.size > availableModules.plus.size) {
					for (const item of availableModules.plus) availableModules.add(item);
					availableModules.plus = set;
				} else {
					for (const item of set) availableModules.add(item);
				}
			};
			// combine minAvailableModules from all resultingAvailableModules
			for (const source of info.availableSources) {
				const resultingAvailableModules =
					calculateResultingAvailableModules(source);
				mergeSet(resultingAvailableModules);
				mergeSet(resultingAvailableModules.plus);
			}
			info.minAvailableModules = availableModules;
			info.minAvailableModulesOwned = false;
			info.resultingAvailableModules = undefined;
			outdatedChunkGroupInfo.add(info);
		}
		chunkGroupsForCombining.clear();
	};

	const processOutdatedChunkGroupInfo = () => {
		statChunkGroupInfoUpdated += outdatedChunkGroupInfo.size;
		// Revisit skipped elements
		for (const info of outdatedChunkGroupInfo) {
			// 1. Reconsider skipped items
			if (info.skippedItems !== undefined) {
				const { minAvailableModules } = info;
				for (const module of info.skippedItems) {
					if (
						!minAvailableModules.has(module) &&
						!minAvailableModules.plus.has(module)
					) {
						queue.push({
							action: ADD_AND_ENTER_MODULE,
							block: module,
							module,
							chunk: info.chunkGroup.chunks[0],
							chunkGroup: info.chunkGroup,
							chunkGroupInfo: info
						});
						info.skippedItems.delete(module);
					}
				}
			}

			// 2. Reconsider skipped connections
			if (info.skippedModuleConnections !== undefined) {
				const { minAvailableModules } = info;
				for (const entry of info.skippedModuleConnections) {
					const [module, activeState] = entry;
					if (activeState === false) continue;
					if (activeState === true) {
						info.skippedModuleConnections.delete(entry);
					}
					if (
						activeState === true &&
						(minAvailableModules.has(module) ||
							minAvailableModules.plus.has(module))
					) {
						info.skippedItems.add(module);
						continue;
					}
					queue.push({
						action: activeState === true ? ADD_AND_ENTER_MODULE : PROCESS_BLOCK,
						block: module,
						module,
						chunk: info.chunkGroup.chunks[0],
						chunkGroup: info.chunkGroup,
						chunkGroupInfo: info
					});
				}
			}

			// 2. Reconsider children chunk groups
			if (info.children !== undefined) {
				statChildChunkGroupsReconnected += info.children.size;
				for (const cgi of info.children) {
					let connectList = queueConnect.get(info);
					if (connectList === undefined) {
						connectList = new Set();
						queueConnect.set(info, connectList);
					}
					connectList.add(cgi);
				}
			}

			// 3. Reconsider chunk groups for combining
			if (info.availableChildren !== undefined) {
				for (const cgi of info.availableChildren) {
					chunkGroupsForCombining.add(cgi);
				}
			}
		}
		outdatedChunkGroupInfo.clear();
	};

	// Iterative traversal of the Module graph
	// Recursive would be simpler to write but could result in Stack Overflows
	while (queue.length || queueConnect.size) {
		logger.time("visitModules: visiting");
		processQueue();
		logger.timeAggregateEnd("visitModules: prepare");
		logger.timeEnd("visitModules: visiting");

		if (chunkGroupsForCombining.size > 0) {
			logger.time("visitModules: combine available modules");
			processChunkGroupsForCombining();
			logger.timeEnd("visitModules: combine available modules");
		}

		if (queueConnect.size > 0) {
			logger.time("visitModules: calculating available modules");
			processConnectQueue();
			logger.timeEnd("visitModules: calculating available modules");

			if (chunkGroupsForMerging.size > 0) {
				logger.time("visitModules: merging available modules");
				processChunkGroupsForMerging();
				logger.timeEnd("visitModules: merging available modules");
			}
		}

		if (outdatedChunkGroupInfo.size > 0) {
			logger.time("visitModules: check modules for revisit");
			processOutdatedChunkGroupInfo();
			logger.timeEnd("visitModules: check modules for revisit");
		}

		// Run queueDelayed when all items of the queue are processed
		// This is important to get the global indexing correct
		// Async blocks should be processed after all sync blocks are processed
		if (queue.length === 0) {
			const tempQueue = queue;
			queue = queueDelayed.reverse();
			queueDelayed = tempQueue;
		}
	}

	logger.log(
		`${statProcessedQueueItems} queue items processed (${statProcessedBlocks} blocks)`
	);
	logger.log(`${statConnectedChunkGroups} chunk groups connected`);
	logger.log(
		`${statProcessedChunkGroupsForMerging} chunk groups processed for merging (${statMergedAvailableModuleSets} module sets, ${statForkedAvailableModules} forked, ${statForkedAvailableModulesCount} + ${statForkedAvailableModulesCountPlus} modules forked, ${statForkedMergedModulesCount} + ${statForkedMergedModulesCountPlus} modules merged into fork, ${statForkedResultModulesCount} resulting modules)`
	);
	logger.log(
		`${statChunkGroupInfoUpdated} chunk group info updated (${statChildChunkGroupsReconnected} already connected chunk groups reconnected)`
	);
};

/**
 *
 * @param {Compilation} compilation the compilation
 * @param {Set<DependenciesBlock>} blocksWithNestedBlocks flag for blocks that have nested blocks
 * @param {Map<AsyncDependenciesBlock, BlockChunkGroupConnection[]>} blockConnections connection for blocks
 * @param {Map<ChunkGroup, ChunkGroupInfo>} chunkGroupInfoMap mapping from chunk group to available modules
 */
const connectChunkGroups = (
	compilation,
	blocksWithNestedBlocks,
	blockConnections,
	chunkGroupInfoMap
) => {
	const { chunkGraph } = compilation;

	/**
	 * Helper function to check if all modules of a chunk are available
	 *
	 * @param {ChunkGroup} chunkGroup the chunkGroup to scan
	 * @param {ModuleSetPlus} availableModules the comparator set
	 * @returns {boolean} return true if all modules of a chunk are available
	 */
	const areModulesAvailable = (chunkGroup, availableModules) => {
		for (const chunk of chunkGroup.chunks) {
			for (const module of chunkGraph.getChunkModulesIterable(chunk)) {
				if (!availableModules.has(module) && !availableModules.plus.has(module))
					return false;
			}
		}
		return true;
	};

	// For each edge in the basic chunk graph
	for (const [block, connections] of blockConnections) {
		// 1. Check if connection is needed
		// When none of the dependencies need to be connected
		// we can skip all of them
		// It's not possible to filter each item so it doesn't create inconsistent
		// connections and modules can only create one version
		// TODO maybe decide this per runtime
		if (
			// TODO is this needed?
			!blocksWithNestedBlocks.has(block) &&
			connections.every(({ chunkGroup, originChunkGroupInfo }) =>
				areModulesAvailable(
					chunkGroup,
					originChunkGroupInfo.resultingAvailableModules
				)
			)
		) {
			continue;
		}

		// 2. Foreach edge
		for (let i = 0; i < connections.length; i++) {
			const { chunkGroup, originChunkGroupInfo } = connections[i];

			// 3. Connect block with chunk
			chunkGraph.connectBlockAndChunkGroup(block, chunkGroup);

			// 4. Connect chunk with parent
			connectChunkGroupParentAndChild(
				originChunkGroupInfo.chunkGroup,
				chunkGroup
			);
		}
	}
};

/**
 * Remove all unconnected chunk groups
 * @param {Compilation} compilation the compilation
 * @param {Iterable<ChunkGroup>} allCreatedChunkGroups all chunk groups that where created before
 */
const cleanupUnconnectedGroups = (compilation, allCreatedChunkGroups) => {
	const { chunkGraph } = compilation;

	for (const chunkGroup of allCreatedChunkGroups) {
		if (chunkGroup.getNumberOfParents() === 0) {
			for (const chunk of chunkGroup.chunks) {
				compilation.chunks.delete(chunk);
				chunkGraph.disconnectChunk(chunk);
			}
			chunkGraph.disconnectChunkGroup(chunkGroup);
			chunkGroup.remove();
		}
	}
};

/**
 * This method creates the Chunk graph from the Module graph
 * @param {Compilation} compilation the compilation
 * @param {Map<Entrypoint, Module[]>} inputEntrypointsAndModules chunk groups which are processed with the modules
 * @returns {void}
 */
const buildChunkGraph = (compilation, inputEntrypointsAndModules) => {
	const logger = compilation.getLogger("webpack.buildChunkGraph");

	// SHARED STATE

	/** @type {Map<AsyncDependenciesBlock, BlockChunkGroupConnection[]>} */
	const blockConnections = new Map();

	/** @type {Set<ChunkGroup>} */
	const allCreatedChunkGroups = new Set();

	/** @type {Map<ChunkGroup, ChunkGroupInfo>} */
	const chunkGroupInfoMap = new Map();

	/** @type {Set<DependenciesBlock>} */
	const blocksWithNestedBlocks = new Set();

	// PART ONE

	logger.time("visitModules");
	visitModules(
		logger,
		compilation,
		inputEntrypointsAndModules,
		chunkGroupInfoMap,
		blockConnections,
		blocksWithNestedBlocks,
		allCreatedChunkGroups
	);
	logger.timeEnd("visitModules");

	// PART TWO

	logger.time("connectChunkGroups");
	connectChunkGroups(
		compilation,
		blocksWithNestedBlocks,
		blockConnections,
		chunkGroupInfoMap
	);
	logger.timeEnd("connectChunkGroups");

	for (const [chunkGroup, chunkGroupInfo] of chunkGroupInfoMap) {
		for (const chunk of chunkGroup.chunks)
			chunk.runtime = mergeRuntime(chunk.runtime, chunkGroupInfo.runtime);
	}

	// Cleanup work

	logger.time("cleanup");
	cleanupUnconnectedGroups(compilation, allCreatedChunkGroups);
	logger.timeEnd("cleanup");
};

module.exports = buildChunkGraph;