Merge pull request #8143 from MLoughry/miclo/optimize-chunk-graph-gen…

…eration

Make changes suggested by @sokra to optimize chunk graph generation

lib/Compilation.js

@@ -92,6 +92,7 @@ const compareLocations = require("./compareLocations");
  * @typedef {Object} AvailableModulesChunkGroupMapping
  * @property {ChunkGroup} chunkGroup
  * @property {Set<Module>} availableModules
+ * @property {boolean} needCopy
  */
 
 /**
@@ -1491,7 +1492,7 @@ class Compilation extends Tapable {
 		//   eachother and Blocks with Chunks. It stops traversing when all modules
 		//   for a chunk are already available. So it doesn't connect unneeded chunks.
 
-		/** @type {Map<ChunkGroup, {block: AsyncDependenciesBlock, chunkGroup: ChunkGroup}[]>} */
+		/** @type {Map<ChunkGroup, {block: AsyncDependenciesBlock, chunkGroup: ChunkGroup, couldBeFiltered: boolean}[]>} */
 		const chunkDependencies = new Map();
 		const allCreatedChunkGroups = new Set();
 
@@ -1664,7 +1665,8 @@ class Compilation extends Tapable {
 			if (!deps) chunkDependencies.set(chunkGroup, (deps = []));
 			deps.push({
 				block: b,
-				chunkGroup: c
+				chunkGroup: c,
+				couldBeFiltered: true
 			});
 
 			// 3. We enqueue the DependenciesBlock for traversal
@@ -1778,12 +1780,14 @@ class Compilation extends Tapable {
 		// PART TWO
 		/** @type {Set<Module>} */
 		let availableModules;
+		/** @type {Set<Module>} */
 		let newAvailableModules;
 		/** @type {Queue<AvailableModulesChunkGroupMapping>} */
 		const queue2 = new Queue(
 			inputChunkGroups.map(chunkGroup => ({
 				chunkGroup,
-				availableModules: new Set()
+				availableModules: new Set(),
+				needCopy: true
 			}))
 		);
 
@@ -1811,8 +1815,12 @@ class Compilation extends Tapable {
 		 */
 		const filterFn = dep => {
 			const depChunkGroup = dep.chunkGroup;
+			if (!dep.couldBeFiltered) return true;
 			if (blocksWithNestedBlocks.has(dep.block)) return true;
-			if (areModulesAvailable(depChunkGroup, newAvailableModules)) return false; // break all modules are already available
+			if (areModulesAvailable(depChunkGroup, newAvailableModules)) {
+				return false; // break all modules are already available
+			}
+			dep.couldBeFiltered = false;
 			return true;
 		};
 
@@ -1831,7 +1839,10 @@ class Compilation extends Tapable {
 			// the list didn't shrink.
 			let minAvailableModules = minAvailableModulesMap.get(chunkGroup);
 			if (minAvailableModules === undefined) {
-				minAvailableModulesMap.set(chunkGroup, new Set(availableModules));
+				minAvailableModulesMap.set(
+					chunkGroup,
+					queueItem.needCopy ? new Set(availableModules) : availableModules
+				);
 			} else {
 				let deletedModules = false;
 				for (const m of minAvailableModules) {
@@ -1857,33 +1868,36 @@ class Compilation extends Tapable {
 				}
 			}
 
-			// 4. Filter edges with available modules
-			const filteredDeps = deps.filter(filterFn);
-
-			// 5. Foreach remaining edge
+			// 4. Foreach remaining edge
 			const nextChunkGroups = new Set();
-			for (let i = 0; i < filteredDeps.length; i++) {
-				const dep = filteredDeps[i];
+			for (let i = 0; i < deps.length; i++) {
+				const dep = deps[i];
+
+				// Filter inline, rather than creating a new array from `.filter()`
+				if (!filterFn(dep)) {
+					continue;
+				}
 				const depChunkGroup = dep.chunkGroup;
 				const depBlock = dep.block;
 
-				// 6. Connect block with chunk
+				// 5. Connect block with chunk
 				GraphHelpers.connectDependenciesBlockAndChunkGroup(
 					depBlock,
 					depChunkGroup
 				);
 
-				// 7. Connect chunk with parent
+				// 6. Connect chunk with parent
 				GraphHelpers.connectChunkGroupParentAndChild(chunkGroup, depChunkGroup);
 
 				nextChunkGroups.add(depChunkGroup);
 			}
 
-			// 8. Enqueue further traversal
+			// 7. Enqueue further traversal
 			for (const nextChunkGroup of nextChunkGroups) {
 				queue2.enqueue({
 					chunkGroup: nextChunkGroup,
-					availableModules: newAvailableModules
+					availableModules: newAvailableModules,
+					needCopy: nextChunkGroup.size !== 1
 				});
 			}
 		}