Log cycles in generated chunks

src/utils/chunkAssignment.ts

@@ -79,7 +79,7 @@ function analyzeModuleGraph(entries: Iterable<Module>): {
 	for (const currentEntry of allEntries) {
 		const modulesToHandle = new Set([currentEntry]);
 		for (const module of modulesToHandle) {
-			getOrCreate(dependentEntriesByModule, module, () => new Set()).add(currentEntry);
+			getOrCreate(dependentEntriesByModule, module, getNewSet).add(currentEntry);
 			for (const dependency of module.getDependenciesToBeIncluded()) {
 				if (!(dependency instanceof ExternalModule)) {
 					modulesToHandle.add(dependency);
@@ -122,7 +122,7 @@ function getDynamicallyDependentEntriesByDynamicEntry(
 		const dynamicDependentEntries = getOrCreate(
 			dynamicallyDependentEntriesByDynamicEntry,
 			dynamicEntry,
-			() => new Set()
+			getNewSet
 		);
 		for (const importer of [
 			...dynamicEntry.includedDynamicImporters,
@@ -147,7 +147,7 @@ function assignEntryToStaticDependencies(
 	const dynamicDependentEntries = dynamicallyDependentEntriesByDynamicEntry.get(entry);
 	const modulesToHandle = new Set([entry]);
 	for (const module of modulesToHandle) {
-		const assignedEntries = getOrCreate(assignedEntriesByModule, module, () => new Set());
+		const assignedEntries = getOrCreate(assignedEntriesByModule, module, getNewSet);
 		if (
 			dynamicDependentEntries &&
 			areEntriesContainedOrDynamicallyDependent(
@@ -258,6 +258,7 @@ function getOptimizedChunks(
 ----- pure  side effects
 small ${`${chunkPartition.small.pure.size}`.padEnd(5, ' ')} ${chunkPartition.small.sideEffect.size}
   big ${`${chunkPartition.big.pure.size}`.padEnd(5, ' ')} ${chunkPartition.big.sideEffect.size}
+Unoptimized chunks contain ${getNumberOfCycles(chunkPartition)} cycles.
 `);
 
 	console.log(
@@ -274,7 +275,9 @@ small ${`${chunkPartition.small.pure.size}`.padEnd(5, ' ')} ${chunkPartition.sma
 	console.log(
 		`${chunkPartition.small.sideEffect.size} chunks smaller than ${prettyBytes(
 			minChunkSize
-		)} with side effects remaining.\n`
+		)} with side effects remaining.\nGenerated chunks contain ${getNumberOfCycles(
+			chunkPartition
+		)} cycles.\n`
 	);
 
 	console.log(
@@ -292,7 +295,7 @@ small ${`${chunkPartition.small.pure.size}`.padEnd(5, ' ')} ${chunkPartition.sma
 	console.log(
 		`${chunkPartition.small.pure.size} pure chunks smaller than ${prettyBytes(
 			minChunkSize
-		)} remaining.\n`
+		)} remaining.\nGenerated chunks contain ${getNumberOfCycles(chunkPartition)} cycles.\n`
 	);
 	timeEnd('optimize chunks', 3);
 	const result = [
@@ -376,6 +379,39 @@ function getPartitionedChunks(
 	};
 }
 
+function getNumberOfCycles(partition: ChunkPartition) {
+	const parents = new Set<ChunkDescription>();
+	const analysedChunks = new Set<ChunkDescription>();
+	let cycles = 0;
+
+	const analyseChunk = (chunk: ChunkDescription) => {
+		for (const dependency of chunk.dependencies) {
+			if (parents.has(dependency)) {
+				if (!analysedChunks.has(dependency)) {
+					cycles++;
+				}
+				continue;
+			}
+			parents.add(dependency);
+			analyseChunk(dependency);
+		}
+		analysedChunks.add(chunk);
+	};
+
+	for (const chunk of [
+		...partition.big.pure,
+		...partition.big.sideEffect,
+		...partition.small.pure,
+		...partition.small.sideEffect
+	]) {
+		if (!parents.has(chunk)) {
+			parents.add(chunk);
+			analyseChunk(chunk);
+		}
+	}
+	return cycles;
+}
+
 function sortChunksAndAddDependencies(
 	chunkLists: ChunkDescription[][],
 	chunkByModule: Map<Module, ChunkDescription>
@@ -526,3 +562,7 @@ function mergeSignatures(sourceSignature: string, targetSignature: string): stri
 	}
 	return signature;
 }
+
+function getNewSet<T>() {
+	return new Set<T>();
+}