feat(commonjs): inject __esModule marker into ES namespaces

Author: lukastaegert

packages/commonjs/src/helpers.js

@@ -37,11 +37,11 @@ export function getDefaultExportFromCjs (x) {
 
 export function createCommonjsModule(fn, basedir, module) {
 	return module = {
-	  path: basedir,
-	  exports: {},
-	  require: function (path, base) {
-      return commonjsRequire(path, (base === undefined || base === null) ? module.path : base);
-    }
+		path: basedir,
+		exports: {},
+		require: function (path, base) {
+			return commonjsRequire(path, (base === undefined || base === null) ? module.path : base);
+		}
 	}, fn(module, module.exports), module.exports;
 }
 
@@ -52,6 +52,20 @@ export function getDefaultExportFromNamespaceIfPresent (n) {
 export function getDefaultExportFromNamespaceIfNotNamed (n) {
 	return n && Object.prototype.hasOwnProperty.call(n, 'default') && Object.keys(n).length === 1 ? n['default'] : n;
 }
+
+export function getAugmentedNamespace(n) {
+	var a = Object.defineProperty({}, '__esModule', {value: true});
+	Object.keys(n).forEach(function (k) {
+		var d = Object.getOwnPropertyDescriptor(n, k);
+		Object.defineProperty(a, k, d.get ? d : {
+			enumerable: true,
+			get: function () {
+				return n[k];
+			}
+		});
+	});
+	return a;
+}
 `;
 
 const HELPER_NON_DYNAMIC = `

packages/commonjs/src/index.js

@@ -189,11 +189,14 @@ export default function commonjs(options = {}) {
 
     transform(code, id) {
       const extName = extname(id);
-      if (extName !== '.cjs' && id !== DYNAMIC_PACKAGES_ID && !id.startsWith(DYNAMIC_JSON_PREFIX)) {
-        if (!filter(id) || !extensions.includes(extName)) {
-          setIsCjsPromise(id, null);
-          return null;
-        }
+      if (
+        extName !== '.cjs' &&
+        id !== DYNAMIC_PACKAGES_ID &&
+        !id.startsWith(DYNAMIC_JSON_PREFIX) &&
+        (!filter(id) || !extensions.includes(extName))
+      ) {
+        setIsCjsPromise(id, null);
+        return null;
       }
 
       let transformed;

packages/commonjs/src/proxies.js

@@ -59,7 +59,9 @@ export async function getStaticRequireProxy(
       !esModulesWithDefaultExport.has(id) ||
       (esModulesWithNamedExports.has(id) && requireReturnsDefault === 'auto'))
   ) {
-    return `import * as ${name} from ${JSON.stringify(id)}; export default ${name};`;
+    return `import {getAugmentedNamespace} from "${HELPERS_ID}"; import * as ${name} from ${JSON.stringify(
+      id
+    )}; export default /*@__PURE__*/getAugmentedNamespace(${name});`;
   }
   return `export {default} from ${JSON.stringify(id)};`;
 }

packages/commonjs/test/fixtures/function/import-esm-with-interop/_config.js

@@ -0,0 +1,3 @@
+module.exports = {
+  description: 'adds the __esModule property when requiring an ES module and support live-bindings'
+};

packages/commonjs/test/fixtures/function/import-esm-with-interop/lib.js

@@ -0,0 +1,9 @@
+/* eslint-disable import/no-mutable-exports */
+let foo = 'foo';
+let bar = 'bar';
+export { foo as default, bar };
+
+export function update(newFoo, newBar) {
+  foo = newFoo;
+  bar = newBar;
+}

packages/commonjs/test/fixtures/function/import-esm-with-interop/main.js

@@ -0,0 +1,15 @@
+/* eslint-disable */
+var lib = require('./lib.js');
+
+function _interopDefault(e) {
+  return e && e.__esModule ? e : { default: e };
+}
+
+var lib__default = /*#__PURE__*/_interopDefault(lib);
+t.is(lib__default['default'], 'foo')
+t.is(lib.bar, 'bar')
+
+lib.update('newFoo', 'newBar');
+t.is(lib__default['default'], 'newFoo')
+t.is(lib.bar, 'newBar')
+