add support for reexporting in CommonJS

and necessary refactoring + fixes for that

Author: sokra

lib/ContextModule.js

@@ -490,6 +490,7 @@ class ContextModule extends Module {
 		const fakeMap = Object.create(null);
 		for (const module of sortedModules) {
 			const exportsType = module.getExportsType(
+				moduleGraph,
 				this.options.namespaceObject === "strict"
 			);
 			const id = chunkGraph.getModuleId(module);

lib/ExportsInfo.js

@@ -425,9 +425,6 @@ class ExportsInfo {
 				return true;
 			}
 		}
-		if (this._sideEffectsOnlyInfo.getUsed(runtime) !== UsageState.Unused) {
-			return true;
-		}
 		for (const exportInfo of this._exports.values()) {
 			if (exportInfo.getUsed(runtime) !== UsageState.Unused) {
 				return true;
@@ -641,7 +638,10 @@ class ExportsInfo {
 	getUsedName(name, runtime) {
 		if (Array.isArray(name)) {
 			// TODO improve this
-			if (name.length === 0) return name;
+			if (name.length === 0) {
+				if (!this.isUsed(runtime)) return false;
+				return name;
+			}
 			let info = this.getReadOnlyExportInfo(name[0]);
 			const x = info.getUsedName(name[0], runtime);
 			if (x === false) return false;

lib/Module.js

@@ -71,7 +71,7 @@ const makeSerializable = require("./util/makeSerializable");
  * @property {string=} exportsArgument
  * @property {boolean=} strict
  * @property {string=} moduleConcatenationBailout
- * @property {("default" | "namespace" | "flagged")=} exportsType
+ * @property {("default" | "namespace" | "flagged" | "dynamic")=} exportsType
  * @property {(false | "redirect" | "redirect-warn")=} defaultObject
  * @property {boolean=} strictHarmonyModule
  * @property {boolean=} async
@@ -263,6 +263,10 @@ class Module extends DependenciesBlock {
 		).getUsedExports(this, undefined);
 	}
 
+	/**
+	 * @deprecated
+	 * @returns {(string | OptimizationBailoutFunction)[]} list
+	 */
 	get optimizationBailout() {
 		return ModuleGraph.getModuleGraphForModule(
 			this,
@@ -372,14 +376,15 @@ class Module extends DependenciesBlock {
 	}
 
 	/**
+	 * @param {ModuleGraph} moduleGraph the module graph
 	 * @param {boolean} strict the importing module is strict
 	 * @returns {"namespace" | "default-only" | "default-with-named" | "dynamic"} export type
 	 * "namespace": Exports is already a namespace object. namespace = exports.
 	 * "dynamic": Check at runtime if __esModule is set. When set: namespace = { ...exports, default: exports }. When not set: namespace = { default: exports }.
 	 * "default-only": Provide a namespace object with only default export. namespace = { default: exports }
 	 * "default-with-named": Provide a namespace object with named and default export. namespace = { ...exports, default: exports }
 	 */
-	getExportsType(strict) {
+	getExportsType(moduleGraph, strict) {
 		switch (this.buildMeta && this.buildMeta.exportsType) {
 			case "flagged":
 				return strict ? "default-only" : "namespace";
@@ -393,6 +398,44 @@ class Module extends DependenciesBlock {
 					default:
 						return "default-only";
 				}
+			case "dynamic": {
+				if (strict) return "default-only";
+				// Try to figure out value of __esModule by following reexports
+				const handleDefault = () => {
+					switch (this.buildMeta.defaultObject) {
+						case "redirect":
+						case "redirect-warn":
+							return "default-with-named";
+						default:
+							return "default-only";
+					}
+				};
+				const exportInfo = moduleGraph.getExportInfo(this, "__esModule");
+				if (exportInfo.provided === false) {
+					return handleDefault();
+				}
+				const target = exportInfo.getTarget(moduleGraph);
+				if (
+					!target ||
+					!target.export ||
+					target.export.length !== 1 ||
+					target.export[0] !== "__esModule"
+				) {
+					return "dynamic";
+				}
+				switch (
+					target.module.buildMeta &&
+					target.module.buildMeta.exportsType
+				) {
+					case "flagged":
+					case "namespace":
+						return "namespace";
+					case "default":
+						return handleDefault();
+					default:
+						return "dynamic";
+				}
+			}
 			default:
 				return strict ? "default-only" : "dynamic";
 		}

lib/RuntimeGlobals.js

@@ -26,7 +26,7 @@ exports.exports = "__webpack_exports__";
 exports.thisAsExports = "top-level-this-exports";
 
 /**
- * top-level this need to be the exports object
+ * runtime need to return the exports of the last entry module
  */
 exports.returnExportsFromRuntime = "return-exports-from-runtime";
 

lib/RuntimeTemplate.js

@@ -357,7 +357,7 @@ class RuntimeTemplate {
 			request,
 			weak
 		});
-		const exportsType = module.getExportsType(strict);
+		const exportsType = module.getExportsType(chunkGraph.moduleGraph, strict);
 		switch (exportsType) {
 			case "namespace":
 				return this.moduleRaw({
@@ -461,7 +461,7 @@ class RuntimeTemplate {
 			request,
 			weak
 		});
-		const exportsType = module.getExportsType(strict);
+		const exportsType = module.getExportsType(chunkGraph.moduleGraph, strict);
 		let fakeType = 0;
 		switch (exportsType) {
 			case "namespace":
@@ -590,6 +590,7 @@ class RuntimeTemplate {
 		const optDeclaration = update ? "" : "var ";
 
 		const exportsType = module.getExportsType(
+			chunkGraph.moduleGraph,
 			originModule.buildMeta.strictHarmonyModule
 		);
 		runtimeRequirements.add(RuntimeGlobals.require);
@@ -646,6 +647,7 @@ class RuntimeTemplate {
 			exportName = exportName ? [exportName] : [];
 		}
 		const exportsType = module.getExportsType(
+			moduleGraph,
 			originModule.buildMeta.strictHarmonyModule
 		);
 

lib/config/defaults.js

@@ -680,7 +680,13 @@ const applyOptimizationDefaults = (
 			apply: compiler => {
 				// Lazy load the Terser plugin
 				const TerserPlugin = require("terser-webpack-plugin");
-				new TerserPlugin().apply(compiler);
+				new TerserPlugin({
+					terserOptions: {
+						compress: {
+							passes: 2
+						}
+					}
+				}).apply(compiler);
 			}
 		}
 	]);

lib/dependencies/CommonJsDependencyHelpers.js

@@ -0,0 +1,49 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+const RuntimeGlobals = require("../RuntimeGlobals");
+
+exports.handleDependencyBase = (depBase, module, runtimeRequirements) => {
+	let base = undefined;
+	let type;
+	switch (depBase) {
+		case "exports":
+			runtimeRequirements.add(RuntimeGlobals.exports);
+			base = module.exportsArgument;
+			type = "expression";
+			break;
+		case "module.exports":
+			runtimeRequirements.add(RuntimeGlobals.module);
+			base = `${module.moduleArgument}.exports`;
+			type = "expression";
+			break;
+		case "this":
+			runtimeRequirements.add(RuntimeGlobals.thisAsExports);
+			base = "this";
+			type = "expression";
+			break;
+		case "Object.defineProperty(exports)":
+			runtimeRequirements.add(RuntimeGlobals.exports);
+			base = module.exportsArgument;
+			type = "Object.defineProperty";
+			break;
+		case "Object.defineProperty(module.exports)":
+			runtimeRequirements.add(RuntimeGlobals.module);
+			base = `${module.moduleArgument}.exports`;
+			type = "Object.defineProperty";
+			break;
+		case "Object.defineProperty(this)":
+			runtimeRequirements.add(RuntimeGlobals.thisAsExports);
+			base = "this";
+			type = "Object.defineProperty";
+			break;
+		default:
+			throw new Error(`Unsupported base ${depBase}`);
+	}
+
+	return [type, base];
+};