support arrow function in umd

lib/library/UmdLibraryPlugin.js

@@ -310,9 +310,11 @@ class UmdLibraryPlugin extends AbstractLibraryPlugin {
 								: "		var a = factory();\n") +
 						  "		for(var i in a) (typeof exports === 'object' ? exports : root)[i] = a[i];\n" +
 						  "	}\n") +
-					`})(${
-						runtimeTemplate.outputOptions.globalObject
-					}, function(${externalsArguments(externals)}) {\nreturn `,
+					`})(${runtimeTemplate.outputOptions.globalObject}, ${
+						runtimeTemplate.supportsArrowFunction()
+							? `(${externalsArguments(externals)}) =>`
+							: `function(${externalsArguments(externals)})`
+					} {\nreturn `,
 				"webpack/universalModuleDefinition"
 			),
 			source,

test/ConfigTestCases.template.js

@@ -619,7 +619,12 @@ const describeCases = config => {
 													const fn = runInNewContext
 														? vm.runInNewContext(code, globalContext, p)
 														: vm.runInThisContext(code, p);
-													fn.call(m.exports, ...argValues);
+													fn.call(
+														testConfig.nonEsmThis
+															? testConfig.nonEsmThis(module)
+															: m.exports,
+														...argValues
+													);
 													document.currentScript = oldCurrentScript;
 													return m.exports;
 												}

test/configCases/umd/issue-15545/index.js

@@ -0,0 +1,5 @@
+it("should compile and run", () => {
+	expect(hello()).toBe("hello");
+});
+
+export function hello() { return "hello"; }

test/configCases/umd/issue-15545/test.config.js

@@ -0,0 +1,9 @@
+const CONTEXT = {};
+module.exports = {
+	nonEsmThis(module) {
+		return CONTEXT;
+	},
+	findBundle() {
+		return ["./runtime.js", "./main.js"];
+	}
+};

test/configCases/umd/issue-15545/webpack.config.js

@@ -0,0 +1,19 @@
+/** @type {import("../../../../").Configuration} */
+module.exports = {
+	mode: "production",
+	entry: {
+		main: "./index.js"
+	},
+	output: {
+		filename: "[name].js",
+		library: "MyLibrary",
+		libraryTarget: "umd",
+		chunkLoading: "jsonp",
+		chunkFormat: "array-push",
+		globalObject: "this"
+	},
+	optimization: {
+		minimize: false,
+		runtimeChunk: "single"
+	}
+};