feat(commonjs): export properties defined using Object.defineProperty…

…(exports, ..) (#222)

* feat: support Object.defineProperty(exports, ..)

* chore: rename defineProperty -> isDefinePropertyCall

* chore: rename isDefinePropertyCall -> getDefinePropertyCallName

packages/commonjs/src/transform.js

@@ -67,6 +67,25 @@ export function checkEsModule(parse, code, id) {
   return { isEsModule, hasDefaultExport: false, ast };
 }
 
+function getDefinePropertyCallName(node, targetName) {
+  if (node.type !== 'CallExpression') return;
+
+  const {
+    callee: { object, property }
+  } = node;
+
+  if (!object || object.type !== 'Identifier' || object.name !== 'Object') return;
+
+  if (!property || property.type !== 'Identifier' || property.name !== 'defineProperty') return;
+
+  if (node.arguments.length !== 3) return;
+
+  const [target, val] = node.arguments;
+  if (target.type !== 'Identifier' || target.name !== targetName) return;
+  // eslint-disable-next-line consistent-return
+  return val.value;
+}
+
 export function transformCommonjs(
   parse,
   code,
@@ -299,6 +318,9 @@ export function transformCommonjs(
         return;
       }
 
+      const name = getDefinePropertyCallName(node, 'exports');
+      if (name && name === makeLegalIdentifier(name)) namedExports[name] = true;
+
       // if this is `var x = require('x')`, we can do `import x from 'x'`
       if (
         node.type === 'VariableDeclarator' &&

packages/commonjs/test/fixtures/samples/define-property/foo.js

@@ -0,0 +1,6 @@
+Object.defineProperty(exports, "foo", {
+  enumerable: true,
+  get: function get() {
+    return "bar";
+  }
+});

packages/commonjs/test/fixtures/samples/define-property/main.js

@@ -0,0 +1 @@
+export { foo } from "./foo";

packages/commonjs/test/test.js

@@ -407,6 +407,15 @@ test('does not reexport named contents', async (t) => {
   }
 });
 
+test(`exports props defined by 'Object.defineProperty'`, async (t) => {
+  const bundle = await rollup({
+    input: 'fixtures/samples/define-property/main.js',
+    plugins: [commonjs()]
+  });
+  const m = await executeBundle(bundle, t);
+  t.is(m.exports.foo, 'bar');
+});
+
 test('respects other plugins', async (t) => {
   const bundle = await rollup({
     input: 'fixtures/samples/other-transforms/main.js',