treat reexports differently from exports

src/Bundle.js

@@ -169,7 +169,18 @@ export default class Bundle {
 					if ( declaration.isNamespace ) {
 						declaration.needsNamespaceBlock = true;
 					}
-				} );
+				});
+
+				entryModule.getReexports().forEach( name => {
+					const declaration = entryModule.traceExport( name );
+
+					if ( declaration.isExternal ) {
+						declaration.reexported = declaration.module.reexported = true;
+					} else {
+						declaration.exportName = name;
+						declaration.activate();
+					}
+				});
 
 				// mark statements that should appear in the bundle
 				if ( this.treeshake ) {
@@ -211,7 +222,7 @@ export default class Bundle {
 				this.externalModules.forEach( module => {
 					const unused = Object.keys( module.declarations )
 						.filter( name => name !== '*' )
-						.filter( name => !module.declarations[ name ].activated );
+						.filter( name => !module.declarations[ name ].activated && !module.declarations[ name ].reexported );
 
 					if ( unused.length === 0 ) return;
 
@@ -471,7 +482,7 @@ export default class Bundle {
 				}
 			} );
 
-			if ( !magicString.toString().trim() && this.entryModule.getExports().length === 0 ) {
+			if ( !magicString.toString().trim() && this.entryModule.getExports().length === 0 && this.entryModule.getReexports().length === 0 ) {
 				this.warn( {
 					code: 'EMPTY_BUNDLE',
 					message: 'Generated an empty bundle'

src/Declaration.js

@@ -48,7 +48,7 @@ export class SyntheticNamespaceDeclaration {
 		this.needsNamespaceBlock = false;
 
 		this.originals = blank();
-		module.getExports().forEach( name => {
+		module.getExports().concat( module.getReexports() ).forEach( name => {
 			this.originals[ name ] = module.traceExport( name );
 		});
 	}

src/Module.js

@@ -303,28 +303,28 @@ export default class Module {
 	}
 
 	getExports () {
-		const exports = blank();
+		return keys( this.exports );
+	}
 
-		keys( this.exports ).forEach( name => {
-			exports[ name ] = true;
-		} );
+	getReexports () {
+		const reexports = blank();
 
 		keys( this.reexports ).forEach( name => {
-			exports[ name ] = true;
+			reexports[ name ] = true;
 		} );
 
 		this.exportAllModules.forEach( module => {
 			if ( module.isExternal ) {
-				exports[ `*${module.id}` ] = true;
+				reexports[ `*${module.id}` ] = true;
 				return;
 			}
 
-			module.getExports().forEach( name => {
-				if ( name !== 'default' ) exports[ name ] = true;
+			module.getExports().concat( module.getReexports() ).forEach( name => {
+				if ( name !== 'default' ) reexports[ name ] = true;
 			} );
 		} );
 
-		return keys( exports );
+		return keys( reexports );
 	}
 
 	namespace () {

src/finalisers/cjs.js

@@ -31,7 +31,9 @@ export default function cjs ( bundle, magicString, { exportMode, intro, outro },
 				const activated = Object.keys( module.declarations )
 					.filter( name => module.declarations[ name ].activated );
 
-				return activated.length ?
+				const needsVar = activated.length || module.reexported;
+
+				return needsVar ?
 					`${varOrConst} ${module.name} = require('${module.path}');` :
 					`require('${module.path}');`;
 			}

src/finalisers/es.js

@@ -62,7 +62,7 @@ export default function es ( bundle, magicString, { intro, outro } ) {
 
 	const exportAllDeclarations = [];
 
-	const specifiers = module.getExports()
+	const specifiers = module.getExports().concat( module.getReexports() )
 		.filter( notDefault )
 		.map( name => {
 			const declaration = module.traceExport( name );

src/finalisers/shared/getExportBlock.js

@@ -5,7 +5,7 @@ export default function getExportBlock ( bundle, exportMode, mechanism = 'return
 		return `${mechanism} ${entryModule.traceExport( 'default' ).getName( false )};`;
 	}
 
-	return entryModule.getExports()
+	const exports = entryModule.getExports().concat( entryModule.getReexports() )
 		.map( name => {
 			if ( name[0] === '*' ) {
 				// export all from external
@@ -27,7 +27,9 @@ export default function getExportBlock ( bundle, exportMode, mechanism = 'return
 			if ( lhs === rhs ) return null;
 
 			return `${lhs} = ${rhs};`;
-		})
+		});
+
+	return exports
 		.filter( Boolean )
 		.join( '\n' );
 }