skip adding es module if already existing

Author: guybedford

src/index.js

@@ -34,6 +34,14 @@ export default function ({ types: t }) {
 
   return {
     visitor: {
+      StringLiteral (path) {
+        if (path.node.value === '__esModule')
+          this.hasEsModule = true;
+      },
+      MemberExpression (path) {
+        if (path.node.property.name === '__esModule')
+          this.hasEsModule = true;
+      },
       Program: {
         enter({ scope }) {
           // "import" existing global variables values as `var foo = $__global["foo"];`
@@ -86,7 +94,7 @@ export default function ({ types: t }) {
 
           const systemGlobal = t.identifier(opts.systemGlobal || "System");
 
-          const factory = (opts.esModule ? buildFactoryEs : buildFactory)({
+          const factory = (opts.esModule && !this.hasEsModule ? buildFactoryEs : buildFactory)({
             SYSTEM_GLOBAL: systemGlobal,
             EXPORT_NAME: exportName,
             GLOBALS: globals || t.nullLiteral(),

test/fixtures/es-module-has/actual.js

@@ -0,0 +1,6 @@
+var foo = function bar() {
+};
+
+Object.defineProperty(foo, '__esModule', {
+  value: true
+});

test/fixtures/es-module-has/expected.js

@@ -0,0 +1,15 @@
+System.registerDynamic([], false, function ($__require, $__exports, $__module) {
+  var _retrieveGlobal = System.registry.get("@@global-helpers").prepareGlobal($__module.id, null, null);
+
+  (function ($__global) {
+    var foo = $__global['foo'];
+    var foo = function bar() {};
+
+    Object.defineProperty(foo, '__esModule', {
+      value: true
+    });
+    $__global['foo'] = foo;
+  })(this);
+
+  return _retrieveGlobal();
+});

test/fixtures/es-module-has/options.js

@@ -0,0 +1,3 @@
+module.exports = {
+  esModule: true
+};