Merge pull request #11999 from webpack/bugfix/11990

fixes unused export bug

lib/ExportsInfo.js

@@ -1211,25 +1211,27 @@ class ExportInfo {
 	 * @param {ModuleGraph} moduleGraph the module graph
 	 * @param {function({ module: Module, export: string[] | undefined }): boolean} resolveTargetFilter filter function to further resolve target
 	 * @param {Set<ExportInfo> | undefined} alreadyVisited set of already visited export info to avoid circular references
-	 * @returns {{ module: Module, export: string[] | undefined } | CIRCULAR | undefined} the target
+	 * @returns {{ module: Module, connection: ModuleGraphConnection, export: string[] | undefined } | CIRCULAR | undefined} the target
 	 */
 	_getTarget(moduleGraph, resolveTargetFilter, alreadyVisited) {
 		/**
 		 * @param {{ connection: ModuleGraphConnection, export: string[] | undefined } | null} inputTarget unresolved target
 		 * @param {Set<ExportInfo>} alreadyVisited set of already visited export info to avoid circular references
-		 * @returns {{ module: Module, export: string[] | undefined } | CIRCULAR | null} resolved target
+		 * @returns {{ module: Module, connection: ModuleGraphConnection, export: string[] | undefined } | CIRCULAR | null} resolved target
 		 */
 		const resolveTarget = (inputTarget, alreadyVisited) => {
 			if (!inputTarget) return null;
 			if (!inputTarget.export) {
 				return {
 					module: inputTarget.connection.module,
+					connection: inputTarget.connection,
 					export: undefined
 				};
 			}
-			/** @type {{ module: Module, export: string[] | undefined }} */
+			/** @type {{ module: Module, connection: ModuleGraphConnection, export: string[] | undefined }} */
 			let target = {
 				module: inputTarget.connection.module,
+				connection: inputTarget.connection,
 				export: inputTarget.export
 			};
 			if (!resolveTargetFilter(target)) return target;
@@ -1252,6 +1254,7 @@ class ExportInfo {
 				} else {
 					target = {
 						module: newTarget.module,
+						connection: newTarget.connection,
 						export: newTarget.export
 							? newTarget.export.concat(target.export.slice(1))
 							: target.export.slice(1)
@@ -1290,6 +1293,24 @@ class ExportInfo {
 		return target;
 	}
 
+	/**
+	 * Move the target forward as long resolveTargetFilter is fulfilled
+	 * @param {ModuleGraph} moduleGraph the module graph
+	 * @param {function({ module: Module, export: string[] | undefined }): boolean} resolveTargetFilter filter function to further resolve target
+	 * @returns {{ module: Module, export: string[] | undefined } | undefined} the target
+	 */
+	moveTarget(moduleGraph, resolveTargetFilter) {
+		const target = this._getTarget(moduleGraph, resolveTargetFilter, undefined);
+		if (target === CIRCULAR) return undefined;
+		if (!target) return undefined;
+		this._target.clear();
+		this._target.set(undefined, {
+			connection: target.connection,
+			export: target.export
+		});
+		return target;
+	}
+
 	createNestedExportsInfo() {
 		if (this.exportsInfoOwned) return this.exportsInfo;
 		this.exportsInfoOwned = true;

lib/optimize/SideEffectsFlagPlugin.js

@@ -232,16 +232,31 @@ class SideEffectsFlagPlugin {
 								module
 							)) {
 								const dep = connection.dependency;
+								let isReexport;
 								if (
-									dep instanceof HarmonyExportImportedSpecifierDependency ||
+									(isReexport =
+										dep instanceof HarmonyExportImportedSpecifierDependency) ||
 									(dep instanceof HarmonyImportSpecifierDependency &&
 										!dep.namespaceObjectAsContext)
 								) {
+									// TODO improve for export *
+									if (isReexport && dep.name) {
+										const exportInfo = moduleGraph.getExportInfo(
+											connection.originModule,
+											dep.name
+										);
+										exportInfo.moveTarget(
+											moduleGraph,
+											({ module }) =>
+												module.getSideEffectsConnectionState(moduleGraph) ===
+												false
+										);
+									}
 									// TODO improve for nested imports
 									const ids = dep.getIds(moduleGraph);
 									if (ids.length > 0) {
 										const exportInfo = exportsInfo.getExportInfo(ids[0]);
-										const target = exportInfo.getTarget(
+										const target = exportInfo.moveTarget(
 											moduleGraph,
 											({ module }) =>
 												module.getSideEffectsConnectionState(moduleGraph) ===

test/cases/scope-hoisting/side-effects-11990-star/chunk1.js

@@ -0,0 +1,2 @@
+import { value3 } from "./reexport";
+expect(value3).toBe(42);

test/cases/scope-hoisting/side-effects-11990-star/chunk2.js

@@ -0,0 +1,2 @@
+import { value2 } from "./module";
+expect(value2).toBe(42);

test/cases/scope-hoisting/side-effects-11990-star/index.js

@@ -0,0 +1,9 @@
+import { value, value3 } from "./reexport";
+
+it("should generate working code", () => {
+	expect(value).toBe(42);
+	expect(value3).toBe(42);
+});
+
+it("should run the chunk1", () => import("./chunk1"));
+it("should run the chunk2", () => import("./chunk2"));

test/cases/scope-hoisting/side-effects-11990-star/module-concat.js

@@ -0,0 +1 @@
+export default 42;

test/cases/scope-hoisting/side-effects-11990-star/module.js

@@ -0,0 +1,2 @@
+export const value = 42;
+export const value2 = 42;

test/cases/scope-hoisting/side-effects-11990-star/package.json

@@ -0,0 +1,5 @@
+{
+  "sideEffects": [
+    "./reexport.js"
+  ]
+}

test/cases/scope-hoisting/side-effects-11990-star/reexport-concat.js

@@ -0,0 +1 @@
+export default 42;

test/cases/scope-hoisting/side-effects-11990-star/reexport.js

@@ -0,0 +1,4 @@
+export * from "./reexport2";
+import { value4 } from "./reexport2";
+import v from "./reexport-concat";
+export const value3 = v + value4 - value4;

test/cases/scope-hoisting/side-effects-11990-star/reexport2.js

@@ -0,0 +1,3 @@
+export * from "./module";
+export const value4 = 42;
+module.id;

test/cases/scope-hoisting/side-effects-11990/chunk1.js

@@ -0,0 +1,2 @@
+import { value3 } from "./reexport";
+expect(value3).toBe(42);

test/cases/scope-hoisting/side-effects-11990/chunk2.js

@@ -0,0 +1,2 @@
+import { value2 } from "./module";
+expect(value2).toBe(42);

test/cases/scope-hoisting/side-effects-11990/index.js

@@ -0,0 +1,9 @@
+import { value, value3 } from "./reexport";
+
+it("should generate working code", () => {
+	expect(value).toBe(42);
+	expect(value3).toBe(42);
+});
+
+it("should run the chunk1", () => import("./chunk1"));
+it("should run the chunk2", () => import("./chunk2"));

test/cases/scope-hoisting/side-effects-11990/module-concat.js

@@ -0,0 +1 @@
+export default 42;

test/cases/scope-hoisting/side-effects-11990/module.js

@@ -0,0 +1,2 @@
+export const value = 42;
+export const value2 = 42;

test/cases/scope-hoisting/side-effects-11990/package.json

@@ -0,0 +1,5 @@
+{
+  "sideEffects": [
+    "./reexport.js"
+  ]
+}

test/cases/scope-hoisting/side-effects-11990/reexport-concat.js

@@ -0,0 +1 @@
+export default 42;

test/cases/scope-hoisting/side-effects-11990/reexport.js

@@ -0,0 +1,4 @@
+export { value } from "./reexport2";
+import { value4 } from "./reexport2";
+import v from "./reexport-concat";
+export const value3 = v + value4 - value4;

test/cases/scope-hoisting/side-effects-11990/reexport2.js

@@ -0,0 +1,3 @@
+export { value } from "./module";
+export const value4 = 42;
+module.id;

types.d.ts

@@ -3030,6 +3030,14 @@ declare abstract class ExportInfo {
 			export: string[];
 		}) => boolean
 	): { module: Module; export: string[] };
+
+	/**
+	 * Move the target forward as long resolveTargetFilter is fulfilled
+	 */
+	moveTarget(
+		moduleGraph: ModuleGraph,
+		resolveTargetFilter: (arg0: { module: Module; export: string[] }) => boolean
+	): { module: Module; export: string[] };
 	createNestedExportsInfo(): ExportsInfo;
 	getNestedExportsInfo(): ExportsInfo;
 	updateHash(hash?: any, runtime?: any): void;