fix: module library when exports are provided unknownly (#20293)

hai-x · web-flow · commit 7dd5e42495a3 · 2026-01-13T18:08:16.000+03:00
=
diff --git a/.changeset/tender-pillows-build.md b/.changeset/tender-pillows-build.md
@@ -0,0 +1,5 @@
+---
+"webpack": patch
+---
+
+Preserve star exports for dependencies in ESMA module output.
diff --git a/lib/library/ModuleLibraryPlugin.js b/lib/library/ModuleLibraryPlugin.js
@@ -7,8 +7,10 @@
 
 const { ConcatSource } = require("webpack-sources");
 const { UsageState } = require("../ExportsInfo");
+const ExternalModule = require("../ExternalModule");
 const RuntimeGlobals = require("../RuntimeGlobals");
 const Template = require("../Template");
+const HarmonyExportImportedSpecifierDependency = require("../dependencies/HarmonyExportImportedSpecifierDependency");
 const ConcatenatedModule = require("../optimize/ConcatenatedModule");
 const propertyAccess = require("../util/propertyAccess");
 const { getEntryRuntime } = require("../util/runtime");
@@ -20,11 +22,14 @@ const AbstractLibraryPlugin = require("./AbstractLibraryPlugin");
 /** @typedef {import("../../declarations/WebpackOptions").LibraryExport} LibraryExport */
 /** @typedef {import("../Chunk")} Chunk */
 /** @typedef {import("../Compiler")} Compiler */
+/** @typedef {import("../ModuleGraph")} ModuleGraph */
 /** @typedef {import("../Module")} Module */
 /** @typedef {import("../Module").BuildMeta} BuildMeta */
 /** @typedef {import("../Module").RuntimeRequirements} RuntimeRequirements */
 /** @typedef {import("../javascript/JavascriptModulesPlugin").StartupRenderContext} StartupRenderContext */
 /** @typedef {import("../javascript/JavascriptModulesPlugin").ModuleRenderContext} ModuleRenderContext */
+/** @typedef {import("../util/runtime").RuntimeSpec} RuntimeSpec */
+/** @typedef {import("../RuntimeTemplate")} RuntimeTemplate */
 
 /**
  * @template T
@@ -116,8 +121,13 @@ class ModuleLibraryPlugin extends AbstractLibraryPlugin {
 			exportsInfo.canMangleUse = false;
 		} else {
 			const exportsInfo = moduleGraph.getExportsInfo(module);
-			// If the entry module is commonjs, its exports cannot be mangled
-			if (module.buildMeta && module.buildMeta.treatAsCommonJs) {
+
+			if (
+				// If the entry module is commonjs, its exports cannot be mangled
+				(module.buildMeta && module.buildMeta.treatAsCommonJs) ||
+				// The entry module provides unknown exports
+				exportsInfo._otherExportsInfo.provided === null
+			) {
 				exportsInfo.setUsedInUnknownWay(runtime);
 			} else {
 				exportsInfo.setAllKnownExportsUsed(runtime);
@@ -144,6 +154,94 @@ class ModuleLibraryPlugin extends AbstractLibraryPlugin {
 		};
 	}
 
+	/**
+	 * @param {Source} source source
+	 * @param {Module} module module
+	 * @param {ModuleGraph} moduleGraph moduleGraph
+	 * @param {RuntimeSpec} runtime chunk runtime
+	 * @param {[string, string][]} exports exports
+	 * @param {Set<string>} alreadyRenderedExports already rendered exports
+	 * @returns {ConcatSource} source with null provided exports
+	 */
+	_analyzeUnknownProvidedExports(
+		source,
+		module,
+		moduleGraph,
+		runtime,
+		exports,
+		alreadyRenderedExports
+	) {
+		const result = new ConcatSource(source);
+		/** @type {Set<string>} */
+		const moduleRequests = new Set();
+		/** @type {Map<string, string>} */
+		const unknownProvidedExports = new Map();
+
+		/**
+		 * @param {Module} module the module
+		 * @param {boolean} isDynamicReexport if module is dynamic reexported
+		 */
+		const resolveDynamicStarReexport = (module, isDynamicReexport) => {
+			for (const connection of moduleGraph.getOutgoingConnections(module)) {
+				const dep = connection.dependency;
+
+				// Only handle star-reexport statement
+				if (
+					dep instanceof HarmonyExportImportedSpecifierDependency &&
+					dep.name === null
+				) {
+					const importedModule = connection.resolvedModule;
+					const importedModuleExportsInfo =
+						moduleGraph.getExportsInfo(importedModule);
+
+					// The imported module provides unknown exports
+					// So keep the reexports rendered in the bundle
+					if (
+						dep.getMode(moduleGraph, runtime).type === "dynamic-reexport" &&
+						importedModuleExportsInfo._otherExportsInfo.provided === null
+					) {
+						// Handle export * from 'external'
+						if (importedModule instanceof ExternalModule) {
+							moduleRequests.add(importedModule.userRequest);
+						} else {
+							resolveDynamicStarReexport(importedModule, true);
+						}
+					}
+					// If importer modules existing `dynamic-reexport` dependency
+					// We should keep export statement rendered in the bundle
+					else if (isDynamicReexport) {
+						for (const exportInfo of importedModuleExportsInfo.orderedExports) {
+							if (!exportInfo.provided || exportInfo.name === "default") {
+								continue;
+							}
+							const originalName = exportInfo.name;
+							const usedName = exportInfo.getUsedName(originalName, runtime);
+
+							if (!alreadyRenderedExports.has(originalName) && usedName) {
+								unknownProvidedExports.set(originalName, usedName);
+							}
+						}
+					}
+				}
+			}
+		};
+
+		resolveDynamicStarReexport(module, false);
+
+		for (const request of moduleRequests) {
+			result.add(`export * from "${request}";\n`);
+		}
+
+		for (const [origin, used] of unknownProvidedExports) {
+			exports.push([
+				origin,
+				`${RuntimeGlobals.exports}${propertyAccess([used])}`
+			]);
+		}
+
+		return result;
+	}
+
 	/**
 	 * @param {Source} source source
 	 * @param {Module} module module
@@ -164,9 +262,8 @@ class ModuleLibraryPlugin extends AbstractLibraryPlugin {
 		},
 		{ options, compilation }
 	) {
-		const result = new ConcatSource(source);
-
-		const exportsInfo = options.export
+		let result = new ConcatSource(source);
+		const exportInfos = options.export
 			? [
 					moduleGraph.getExportInfo(
 						module,
@@ -188,6 +285,9 @@ class ModuleLibraryPlugin extends AbstractLibraryPlugin {
 		const shortHandedExports = [];
 		/** @type {[string, string][]} */
 		const exports = [];
+		/** @type {Set<string>} */
+		const alreadyRenderedExports = new Set();
+
 		const isAsync = moduleGraph.isAsync(module);
 
 		const treatAsCommonJs =
@@ -200,7 +300,7 @@ class ModuleLibraryPlugin extends AbstractLibraryPlugin {
 			);
 		}
 
-		outer: for (const exportInfo of exportsInfo) {
+		outer: for (const exportInfo of exportInfos) {
 			if (!exportInfo.provided) continue;
 
 			const originalName = exportInfo.name;
@@ -273,6 +373,8 @@ class ModuleLibraryPlugin extends AbstractLibraryPlugin {
 						: `${finalName} as ${originalName}`
 				);
 			}
+
+			alreadyRenderedExports.add(originalName);
 		}
 
 		if (treatAsCommonJs) {
@@ -283,6 +385,15 @@ class ModuleLibraryPlugin extends AbstractLibraryPlugin {
 			result.add(`export { ${shortHandedExports.join(", ")} };\n`);
 		}
 
+		result = this._analyzeUnknownProvidedExports(
+			result,
+			module,
+			moduleGraph,
+			chunk.runtime,
+			exports,
+			alreadyRenderedExports
+		);
+
 		for (const [exportName, final] of exports) {
 			result.add(
 				`export ${runtimeTemplate.renderConst()} ${exportName} = ${final};\n`
diff --git a/test/configCases/library/0-create-library/esm-star-reexport-and-external/bar.js b/test/configCases/library/0-create-library/esm-star-reexport-and-external/bar.js
@@ -0,0 +1,2 @@
+export const foo = 3;
+export const bar = 3;
diff --git a/test/configCases/library/0-create-library/esm-star-reexport-and-external/foo.js b/test/configCases/library/0-create-library/esm-star-reexport-and-external/foo.js
@@ -0,0 +1,2 @@
+export const foo = 2;
+export const bar = 2;
diff --git a/test/configCases/library/0-create-library/esm-star-reexport-and-external/index.js b/test/configCases/library/0-create-library/esm-star-reexport-and-external/index.js
@@ -0,0 +1,6 @@
+export * from "fs";
+export * from "./reexport-foo";
+export * from "./reexport-bar";
+
+export const foo = 1;
+export const bar = 1;
diff --git a/test/configCases/library/0-create-library/esm-star-reexport-and-external/reexport-bar.js b/test/configCases/library/0-create-library/esm-star-reexport-and-external/reexport-bar.js
@@ -0,0 +1,2 @@
+export * from "path";
+export * from "./bar";
diff --git a/test/configCases/library/0-create-library/esm-star-reexport-and-external/reexport-foo.js b/test/configCases/library/0-create-library/esm-star-reexport-and-external/reexport-foo.js
@@ -0,0 +1 @@
+export * from "./foo";
diff --git a/test/configCases/library/0-create-library/webpack.config.js b/test/configCases/library/0-create-library/webpack.config.js
@@ -934,5 +934,20 @@ module.exports = (env, { testPath }) => [
 				type: "system"
 			}
 		}
+	},
+	{
+		entry: "./esm-star-reexport-and-external",
+		target: "node14",
+		output: {
+			uniqueName: "esm-star-reexport-and-external",
+			filename: "esm-star-reexport-and-external.mjs",
+			module: true,
+			library: {
+				type: "module"
+			}
+		},
+		experiments: {
+			outputModule: true
+		}
 	}
 ];
diff --git a/test/configCases/library/1-use-library/esm-star-reexport-and-external.js b/test/configCases/library/1-use-library/esm-star-reexport-and-external.js
@@ -0,0 +1,13 @@
+import { readFile, foo, bar, resolve } from "library";
+import fs from "fs"
+import path from "path"
+
+it("should handle external module correctly with star reexports", () => {
+	// `foo` and `bar` are reexported by `reexport-foo` module and `reexport-bar` module,
+	// but the entry module's exports take precedence.
+	expect(foo).toBe(1);
+	expect(bar).toBe(1);
+
+	expect(readFile).toBe(fs.readFile);
+	expect(resolve).toBe(path.resolve);
+});
diff --git a/test/configCases/library/1-use-library/webpack.config.js b/test/configCases/library/1-use-library/webpack.config.js
@@ -734,5 +734,16 @@ module.exports = (env, { testPath }) => [
 				NAME: JSON.stringify("commonjs-bundle-to-esm")
 			})
 		]
+	},
+	{
+		entry: "./esm-star-reexport-and-external",
+		resolve: {
+			alias: {
+				library: path.resolve(
+					testPath,
+					"../0-create-library/esm-star-reexport-and-external.mjs"
+				)
+			}
+		}
 	}
 ];

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +---
 +"webpack": patch
 +---
++
 +Preserve star exports for dependencies in ESMA module output.
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+export const foo = 3;`
	`2`	`+export const bar = 3;`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+export const foo = 2;`
	`2`	`+export const bar = 2;`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+export * from "path";`
	`2`	`+export * from "./bar";`