default exports are not bound. fixes #15

src/Bundle.js

@@ -238,6 +238,13 @@ export default class Bundle {
 		let previousIndex = -1;
 		let previousMargin = 0;
 
+		// within a module, statements should preserve their original order
+		// TODO is this foolproof?
+		this.statements.sort( ( a, b ) => {
+			if ( a.module !== b.module ) return -1; // no change
+			return a.index - b.index;
+		});
+
 		this.statements.forEach( statement => {
 			// skip `export { foo, bar, baz }`
 			if ( statement.node.type === 'ExportNamedDeclaration' && statement.node.specifiers.length ) {

src/Module.js

@@ -99,13 +99,16 @@ export default class Module {
 			if ( node.type === 'ExportDefaultDeclaration' ) {
 				const isDeclaration = /Declaration$/.test( node.declaration.type );
 				const declaredName = isDeclaration && node.declaration.id.name;
+				const identifier = node.declaration.type === 'Identifier' && node.declaration.name;
 
 				this.exports.default = {
 					statement,
 					name: 'default',
 					localName: declaredName || 'default',
 					declaredName,
-					isDeclaration
+					identifier,
+					isDeclaration,
+					isModified: false // in case of `export default foo; foo = somethingElse`
 				};
 			}
 
@@ -207,6 +210,16 @@ export default class Module {
 	}
 
 	getCanonicalName ( localName ) {
+		// Special case
+		if ( localName === 'default' && this.exports.default && this.exports.default.isModified ) {
+			let canonicalName = makeLegalIdentifier( this.path.replace( this.bundle.base + '/', '' ).replace( /\.js$/, '' ) );
+			while ( this.definitions[ canonicalName ] ) {
+				canonicalName = `_${canonicalName}`;
+			}
+
+			return canonicalName;
+		}
+
 		if ( this.suggestedNames[ localName ] ) {
 			localName = this.suggestedNames[ localName ];
 		}
@@ -358,7 +371,7 @@ export default class Module {
 				if ( !statement.node.specifiers.length ) {
 					return this.bundle.fetchModule( statement.node.source.value, this.path )
 						.then( module => {
-							statement.module = module; // TODO what is this for? what does it do? why not _module?
+							statement.module = module;
 							return module.expandAllStatements();
 						})
 						.then( statements => {

src/Statement.js

@@ -176,6 +176,17 @@ export default class Statement {
 				return;
 			}
 
+			// special case = `export default foo; foo += 1;` - we'll
+			// need to assign a new variable so that the exported
+			// value is not updated by the second statement
+			if ( this.module.exports.default && this.module.exports.default.identifier === node.name ) {
+				// but only if this is a) inside a function body or
+				// b) after the export declaration
+				if ( !!scope.parent || node.start > this.module.exports.default.statement.node.start ) {
+					this.module.exports.default.isModified = true;
+				}
+			}
+
 			this.modifies[ node.name ] = true;
 		};
 

test/function/default-export-is-not-bound/_config.js

@@ -1,6 +1,5 @@
 module.exports = {
-	description: 'does not bind default exports',
-	skip: true
+	description: 'does not bind default exports'
 };
 
 // test copied from https://github.com/esnext/es6-module-transpiler/tree/master/test/examples/export-default

test/function/default-export-is-not-bound/main.js

@@ -1,6 +1,6 @@
 import value from './foo';
 import { change } from './foo';
 
-assert.equal(value, 42);
+assert.equal( value, 42 );
 change();
 assert.equal( value, 42, 'default export should not be bound' );