fix: default import of commonjs externals for SystemJS format

lib/library/SystemLibraryPlugin.js

@@ -134,11 +134,21 @@ class SystemLibraryPlugin extends AbstractLibraryPlugin {
 										);
 										if (used) {
 											if (otherUnused || used !== exportInfo.name) {
+												if (exportInfo.name === "default") {
+													// Ideally we should use `module && module.__esModule ? module['default'] : module`
+													// But we need to keep compatibility with SystemJS format libraries (they are using `default`) and bundled SystemJS libraries from commonjs format
+													instructions.push(
+														`${external}${propertyAccess([
+															used
+														])} = module["default"] || module;`
+													);
+												} else {
 													instructions.push(
 														`${external}${propertyAccess([
 															used
 														])} = module${propertyAccess([exportInfo.name])};`
 													);
+												}
 												handledNames.push(exportInfo.name);
 											}
 										} else {

test/configCases/library/0-create-library/commonjs.js

@@ -0,0 +1,12 @@
+const a = 10;
+const b = 20;
+
+class MyClass {
+	getValue() {
+		return "my-class";
+	}
+}
+
+module.exports = MyClass;
+module.exports.a = a;
+module.exports.b = b;

test/configCases/library/0-create-library/esm.js

@@ -0,0 +1,11 @@
+const a = 10;
+const b = 20;
+
+class MyClass {
+	getValue() {
+		return "my-class";
+	}
+}
+
+export default MyClass;
+export { a, b };

test/configCases/library/0-create-library/webpack.config.js

@@ -914,5 +914,25 @@ module.exports = (env, { testPath }) => [
 		experiments: {
 			outputModule: true
 		}
+	},
+	{
+		entry: "./esm.js",
+		output: {
+			uniqueName: "system-esm",
+			filename: "system-esm.js",
+			library: {
+				type: "system"
+			}
+		}
+	},
+	{
+		entry: "./commonjs.js",
+		output: {
+			uniqueName: "system-commonjs",
+			filename: "system-commonjs.js",
+			library: {
+				type: "system"
+			}
+		}
 	}
 ];

test/configCases/library/1-systemjs-external-commonjs/system-external-commonjs.js

@@ -0,0 +1,7 @@
+import MyClass, {a, b} from "library-commonjs";
+
+it("should get exports from systemjs library (" + NAME + ")", function() {
+	expect(new MyClass().getValue()).toBe("my-class")
+	expect(a).toBe(10);
+	expect(b).toBe(20);
+});

test/configCases/library/1-systemjs-external-commonjs/test.config.js

@@ -0,0 +1,17 @@
+"use strict";
+
+const System = require("../../../helpers/fakeSystem");
+
+module.exports = {
+	beforeExecute: () => {
+		System.init();
+	},
+	moduleScope(scope) {
+		scope.System = System;
+		scope.System.setRequire(scope.require);
+	},
+	afterExecute() {
+		delete global.webpackChunk;
+		System.execute("(anonym)");
+	}
+};

test/configCases/library/1-systemjs-external-commonjs/webpack.config.js

@@ -0,0 +1,27 @@
+"use strict";
+
+const path = require("path");
+const webpack = require("../../../../");
+
+/** @type {(env: Env, options: TestOptions) => import("../../../../").Configuration[]} */
+module.exports = (env, { testPath }) => [
+	{
+		entry: "./system-external-commonjs.js",
+		output: {
+			library: {
+				type: "system"
+			}
+		},
+		externals: {
+			"library-commonjs": path.resolve(
+				testPath,
+				"../0-create-library/system-commonjs.js"
+			)
+		},
+		plugins: [
+			new webpack.DefinePlugin({
+				NAME: JSON.stringify("systemjs with external from commonjs format")
+			})
+		]
+	}
+];

test/configCases/library/1-systemjs-external-esm/system-external-esm.js

@@ -0,0 +1,7 @@
+import MyClass, {a, b} from "library-esm";
+
+it("should get exports from systemjs library (" + NAME + ")", function() {
+	expect(new MyClass().getValue()).toBe("my-class")
+	expect(a).toBe(10);
+	expect(b).toBe(20);
+});

test/configCases/library/1-systemjs-external-esm/test.config.js

@@ -0,0 +1,17 @@
+"use strict";
+
+const System = require("../../../helpers/fakeSystem");
+
+module.exports = {
+	beforeExecute: () => {
+		System.init();
+	},
+	moduleScope(scope) {
+		scope.System = System;
+		scope.System.setRequire(scope.require);
+	},
+	afterExecute() {
+		delete global.webpackChunk;
+		System.execute("(anonym)");
+	}
+};

test/configCases/library/1-systemjs-external-esm/webpack.config.js

@@ -0,0 +1,24 @@
+"use strict";
+
+const path = require("path");
+const webpack = require("../../../../");
+
+/** @type {(env: Env, options: TestOptions) => import("../../../../").Configuration[]} */
+module.exports = (env, { testPath }) => [
+	{
+		entry: "./system-external-esm.js",
+		output: {
+			library: {
+				type: "system"
+			}
+		},
+		externals: {
+			"library-esm": path.resolve(testPath, "../0-create-library/system-esm.js")
+		},
+		plugins: [
+			new webpack.DefinePlugin({
+				NAME: JSON.stringify("systemjs with external from ES module format")
+			})
+		]
+	}
+];