Merge pull request #48 from rollup/gh-43

Fix #43

src/Bundle.js

@@ -418,7 +418,9 @@ export default class Bundle {
 
 				keys( statement.modifies ).forEach( name => {
 					const definingStatement = module.definitions[ name ];
-					const exportDeclaration = module.exports[ name ];
+					const exportDeclaration = module.exports[ name ] || (
+						module.exports.default && module.exports.default.identifier === name && module.exports.default
+					);
 
 					const shouldMark = ( definingStatement && definingStatement.isIncluded ) ||
 					                   ( exportDeclaration && exportDeclaration.isUsed );

src/Module.js

@@ -412,6 +412,7 @@ export default class Module {
 						});
 					}
 
+					exportDeclaration.isUsed = true;
 					return module.mark( exportDeclaration.localName );
 				});
 		}

test/function/top-level-side-effect-on-imported/_config.js

@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'top level function calls are preserved'
+};

test/function/top-level-side-effect-on-imported/lib.js

@@ -0,0 +1,5 @@
+import obj from './obj';
+
+obj.value = 'augmented';
+
+export default obj;

test/function/top-level-side-effect-on-imported/main.js

@@ -0,0 +1,3 @@
+import lib from './lib';
+
+assert.strictEqual(lib.value, 'augmented');

test/function/top-level-side-effect-on-imported/obj.js

@@ -0,0 +1 @@
+export default { value: 'original' };