perf: fix regression in module concatenation

lib/ModuleGraph.js

@@ -11,6 +11,7 @@ const ModuleGraphConnection = require("./ModuleGraphConnection");
 const SortableSet = require("./util/SortableSet");
 const WeakTupleMap = require("./util/WeakTupleMap");
 const { sortWithSourceOrder } = require("./util/comparators");
+const memoize = require("./util/memoize");
 
 /** @typedef {import("./Compilation").ModuleMemCaches} ModuleMemCaches */
 /** @typedef {import("./DependenciesBlock")} DependenciesBlock */
@@ -24,6 +25,10 @@ const { sortWithSourceOrder } = require("./util/comparators");
 /** @typedef {import("./dependencies/HarmonyImportSpecifierDependency")} HarmonyImportSpecifierDependency */
 /** @typedef {import("./util/comparators").DependencySourceOrder} DependencySourceOrder */
 
+const getCommonJsSelfReferenceDependency = memoize(() =>
+	require("./dependencies/CommonJsSelfReferenceDependency")
+);
+
 /**
  * @callback OptimizationBailoutFunction
  * @param {RequestShortener} requestShortener
@@ -840,8 +845,7 @@ class ModuleGraph {
 		for (const connection of connections) {
 			if (
 				!connection.dependency ||
-				connection.dependency instanceof
-					require("./dependencies/CommonJsSelfReferenceDependency")
+				connection.dependency instanceof getCommonJsSelfReferenceDependency()
 			) {
 				continue;
 			}

lib/config/defaults.js

@@ -384,6 +384,7 @@ const applyExperimentsDefaults = (
 	D(experiments, "lazyCompilation", undefined);
 	D(experiments, "buildHttp", undefined);
 	D(experiments, "cacheUnaffected", experiments.futureDefaults);
+	D(experiments, "deferImport", false);
 	F(experiments, "css", () => (experiments.futureDefaults ? true : undefined));
 
 	// TODO webpack 6: remove this. topLevelAwait should be enabled by default

lib/dependencies/HarmonyExportDependencyParserPlugin.js

@@ -77,7 +77,9 @@ module.exports = class HarmonyExportDependencyParserPlugin {
 			clearDep.loc = /** @type {DependencyLocation} */ (statement.loc);
 			clearDep.loc.index = -1;
 			parser.state.module.addPresentationalDependency(clearDep);
-			const { defer } = getImportMode(parser, statement);
+			let defer = false;
+			if (this.deferImport) {
+				({ defer } = getImportMode(parser, statement));
 				if (defer) {
 					const error = new WebpackError(
 						"Deferred re-export (`export defer * as namespace from '...'`) is not a part of the Import Defer proposal.\nUse the following code instead:\n    import defer * as namespace from '...';\n    export { namespace };"
@@ -85,6 +87,7 @@ module.exports = class HarmonyExportDependencyParserPlugin {
 					error.loc = statement.loc || undefined;
 					parser.state.current.addError(error);
 				}
+			}
 			const sideEffectDep = new HarmonyImportSideEffectDependency(
 				/** @type {string} */ (source),
 				parser.state.lastHarmonyImportOrder,
@@ -202,7 +205,9 @@ module.exports = class HarmonyExportDependencyParserPlugin {
 						parser.state.harmonyStarExports || new HarmonyStarExportsList();
 				}
 				const attributes = getImportAttributes(statement);
-				const { defer } = getImportMode(parser, statement);
+				const defer = this.deferImport
+					? getImportMode(parser, statement).defer
+					: false;
 				const dep = new HarmonyExportImportedSpecifierDependency(
 					/** @type {string} */
 					(source),

lib/dependencies/HarmonyImportDependencyParserPlugin.js

@@ -124,7 +124,9 @@ module.exports = class HarmonyImportDependencyParserPlugin {
 			parser.state.module.addPresentationalDependency(clearDep);
 			parser.unsetAsiPosition(/** @type {Range} */ (statement.range)[1]);
 			const attributes = getImportAttributes(statement);
-			const { defer } = getImportMode(parser, statement);
+			let defer = false;
+			if (this.deferImport) {
+				({ defer } = getImportMode(parser, statement));
 				if (
 					defer &&
 					(statement.specifiers.length !== 1 ||
@@ -136,6 +138,7 @@ module.exports = class HarmonyImportDependencyParserPlugin {
 					error.loc = statement.loc || undefined;
 					parser.state.current.addError(error);
 				}
+			}
 			const sideEffectDep = new HarmonyImportSideEffectDependency(
 				/** @type {string} */ (source),
 				parser.state.lastHarmonyImportOrder,
@@ -150,7 +153,9 @@ module.exports = class HarmonyImportDependencyParserPlugin {
 			PLUGIN_NAME,
 			(statement, source, id, name) => {
 				const ids = id === null ? [] : [id];
-				const { defer } = getImportMode(parser, statement);
+				const defer = this.deferImport
+					? getImportMode(parser, statement).defer
+					: false;
 				parser.tagVariable(name, harmonySpecifierTag, {
 					name,
 					source,
@@ -391,7 +396,7 @@ module.exports = class HarmonyImportDependencyParserPlugin {
 /**
  * @param {JavascriptParser} parser parser
  * @param {ExportNamedDeclaration | ExportAllDeclaration | ImportDeclaration} node node
- * @returns {{defer: boolean}} import attributes
+ * @returns {{ defer: boolean }} import attributes
  */
 function getImportMode(parser, node) {
 	const result = { defer: "phase" in node && node.phase === "defer" };

lib/optimize/ConcatenatedModule.js

@@ -945,7 +945,8 @@ class ConcatenatedModule extends Module {
 		/** @type {Map<Module, RuntimeSpec | true>} */
 		const existingEntries = new Map();
 		const deferEnabled =
-			this.compilation && this.compilation.options.experiments.deferImport;
+			/** @type {Compilation} */
+			(this.compilation).options.experiments.deferImport;
 
 		/**
 		 * @param {Module} module a module
@@ -1712,7 +1713,8 @@ ${defineGetters}`
 		/** @type {InitFragment<ChunkRenderContext>[]} */
 		const chunkInitFragments = [];
 		const deferEnabled =
-			this.compilation && this.compilation.options.experiments.deferImport;
+			/** @type {Compilation} */
+			(this.compilation).options.experiments.deferImport;
 
 		// evaluate modules in order
 		for (const rawInfo of modulesWithInfo) {

lib/optimize/ModuleConcatenationPlugin.js

@@ -149,6 +149,7 @@ class ModuleConcatenationPlugin {
 						chunkGraph,
 						moduleGraph
 					};
+					const deferEnabled = compilation.options.experiments.deferImport;
 					logger.time("select relevant modules");
 					for (const module of modules) {
 						let canBeRoot = true;
@@ -223,7 +224,7 @@ class ModuleConcatenationPlugin {
 							canBeInner = false;
 						}
 
-						if (moduleGraph.isDeferred(module)) {
+						if (deferEnabled && moduleGraph.isDeferred(module)) {
 							setInnerBailoutReason(module, "Module is deferred");
 							canBeInner = false;
 						}

test/Defaults.unittest.js

@@ -97,6 +97,7 @@ describe("snapshots", () => {
 		    "buildHttp": undefined,
 		    "cacheUnaffected": false,
 		    "css": undefined,
+		    "deferImport": false,
 		    "futureDefaults": false,
 		    "layers": false,
 		    "lazyCompilation": undefined,
@@ -2025,9 +2026,10 @@ describe("snapshots", () => {
 			@@ ... @@
 			-     "cacheUnaffected": false,
 			-     "css": undefined,
-			-     "futureDefaults": false,
 			+     "cacheUnaffected": true,
 			+     "css": true,
+			@@ ... @@
+			-     "futureDefaults": false,
 			+     "futureDefaults": true,
 			@@ ... @@
 			+       },
@@ -2491,9 +2493,10 @@ describe("snapshots", () => {
 			@@ ... @@
 			-     "cacheUnaffected": false,
 			-     "css": undefined,
-			-     "futureDefaults": false,
 			+     "cacheUnaffected": true,
 			+     "css": true,
+			@@ ... @@
+			-     "futureDefaults": false,
 			+     "futureDefaults": true,
 			@@ ... @@
 			+       },
@@ -2637,9 +2640,10 @@ describe("snapshots", () => {
 			@@ ... @@
 			-     "cacheUnaffected": false,
 			-     "css": undefined,
-			-     "futureDefaults": false,
 			+     "cacheUnaffected": true,
 			+     "css": false,
+			@@ ... @@
+			-     "futureDefaults": false,
 			+     "futureDefaults": true,
 			@@ ... @@
 			+       },

test/configCases/split-chunks/asnyc-entries/webpack.config.js

@@ -2,6 +2,9 @@
 
 module.exports = {
 	output: {
-		filename: "[name].js"
+		filename: "[name].js",
+		environment: {
+			nodePrefixForCoreModules: false
+		}
 	}
 };