improve way of getting combinations of chunks

we no longer require a complexity limit -> maxComplexity removed

lib/WebpackOptionsDefaulter.js

@@ -168,7 +168,6 @@ class WebpackOptionsDefaulter extends OptionsDefaulter {
 		this.set("optimization.usedExports", "make", options => isProductionLikeMode(options));
 		this.set("optimization.concatenateModules", "make", options => isProductionLikeMode(options));
 		this.set("optimization.splitChunks", {});
-		this.set("optimization.splitChunks.maxComplexity", "make", options => isProductionLikeMode(options) ? 3 : 1);
 		this.set("optimization.splitChunks.chunks", "async");
 		this.set("optimization.splitChunks.minSize", 30000);
 		this.set("optimization.splitChunks.minChunks", 1);

lib/optimize/SplitChunksPlugin.js

@@ -7,6 +7,7 @@
 const crypto = require("crypto");
 const SortableSet = require("../util/SortableSet");
 const GraphHelpers = require("../GraphHelpers");
+const isSubset = require("../util/SetHelpers").isSubset;
 
 const hashFilename = (name) => {
 	return crypto.createHash("md5").update(name).digest("hex").slice(0, 8);
@@ -40,23 +41,6 @@ const isOverlap = (a, b) => {
 	return false;
 };
 
-const getCombinations = (array, maxDepth) => {
-	const results = [];
-	getCombinationsInteral(array, maxDepth, results);
-	return results;
-};
-
-const getCombinationsInteral = (array, maxDepth, results) => {
-	results.push(array);
-	if(maxDepth === 0 || array.length === 1) {
-		return;
-	}
-	for(let i = 0; i < array.length; i++) {
-		const newArray = array.slice(0, i).concat(array.slice(i + 1, array.length));
-		getCombinationsInteral(newArray, maxDepth - 1, results);
-	}
-};
-
 const compareEntries = (a, b) => {
 	// 1. by priority
 	const diffPriority = a.cacheGroup.priority - b.cacheGroup.priority;
@@ -97,7 +81,6 @@ module.exports = class SplitChunksPlugin {
 
 	static normalizeOptions(options) {
 		return {
-			maxComplexity: options.maxComplexity || 0,
 			chunks: options.chunks || "all",
 			minSize: options.minSize || 0,
 			minChunks: options.minChunks || 1,
@@ -227,6 +210,25 @@ module.exports = class SplitChunksPlugin {
 				for(const chunk of chunks) {
 					indexMap.set(chunk, index++);
 				}
+				const getKey = chunks => {
+					return Array.from(chunks, c => indexMap.get(c)).sort().join();
+				};
+				// Create a list of possible combinations
+				const chunkSetsInGraph = new Map(); // Map<string, Set<Chunk>>
+				for(const module of compilation.modules) {
+					const chunkIndices = getKey(module.chunksIterable);
+					chunkSetsInGraph.set(chunkIndices, new Set(module.chunksIterable));
+				}
+				const combinations = new Map(); // Map<string, Set<Chunk>[]>
+				for(const [key, chunksSet] of chunkSetsInGraph) {
+					var array = [];
+					for(const set of chunkSetsInGraph.values()) {
+						if(isSubset(chunksSet, set)) {
+							array.push(set);
+						}
+					}
+					combinations.set(key, array);
+				}
 				// Map a list of chunks to a list of modules
 				// For the key the chunk "index" is used, the value is a SortableSet of modules
 				const chunksInfoMap = new Map();
@@ -249,24 +251,24 @@ module.exports = class SplitChunksPlugin {
 							getName: cacheGroupSource.getName !== undefined ? cacheGroupSource.getName : this.options.getName,
 							reuseExistingChunk: cacheGroupSource.reuseExistingChunk
 						};
-						// Select chunks by configuration
-						const maxSelectedChunks = cacheGroup.chunks === "initial" ? chunks.filter(chunk => chunk.canBeInitial()) :
-							cacheGroup.chunks === "async" ? chunks.filter(chunk => !chunk.canBeInitial()) :
-							chunks;
-						// For all (nearly all) combination of chunk selection
-						for(const selectedChunks of getCombinations(maxSelectedChunks, this.options.maxComplexity)) {
+						// For all combination of chunk selection
+						for(const chunkCombination of combinations.get(getKey(chunks))) {
 							// Get indices of chunks in which this module occurs
-							const chunkIndices = selectedChunks.map(chunk => indexMap.get(chunk));
+							const chunkIndices = Array.from(chunkCombination, chunk => indexMap.get(chunk));
 							// Break if minimum number of chunks is not reached
 							if(chunkIndices.length < cacheGroup.minChunks)
 								continue;
+							// Select chunks by configuration
+							const selectedChunks = cacheGroup.chunks === "initial" ? Array.from(chunkCombination).filter(chunk => chunk.canBeInitial()) :
+								cacheGroup.chunks === "async" ? Array.from(chunkCombination).filter(chunk => !chunk.canBeInitial()) :
+								Array.from(chunkCombination);
 							// Determine name for split chunk
 							const name = cacheGroup.getName(module, selectedChunks, cacheGroup.key);
 							// Create key for maps
 							// When it has a name we use the name as key
 							// Elsewise we create the key from chunks and cache group key
 							// This automatically merges equal names
-							const chunksKey = chunkIndices.sort().join();
+							const chunksKey = getKey(selectedChunks);
 							const key = name && `name:${name}` ||
 								`chunks:${chunksKey} key:${cacheGroup.key}`;
 							// Add module to maps

lib/util/SetHelpers.js

@@ -24,3 +24,11 @@ exports.intersect = sets => {
 	}
 	return current;
 };
+
+exports.isSubset = (bigSet, smallSet) => {
+	if(bigSet.size < smallSet.size) return false;
+	for(const item of smallSet) {
+		if(!bigSet.has(item)) return false;
+	}
+	return true;
+};

schemas/WebpackOptions.json

@@ -1335,11 +1335,6 @@
               "type": "object",
               "additionalProperties": false,
               "properties": {
-                "maxComplexity": {
-                  "description": "Limits the algorithmic complexity",
-                  "type": "number",
-                  "minimum": 0
-                },
                 "chunks": {
                   "description": "Select chunks for determining shared modules (defaults to \"async\", \"initial\" and \"all\" requires adding these chunks to the HTML)",
                   "enum": [

test/statsCases/split-chunks-combinations/webpack.config.js

@@ -18,7 +18,6 @@ module.exports = {
 	},
 	optimization: {
 		splitChunks: {
-			maxComplexity: 100,
 			minSize: 100
 		}
 	},