optimize ns["foo"] (#841)

src/ast/nodes/MemberExpression.js

@@ -1,14 +1,24 @@
-import isReference from 'is-reference';
 import relativeId from '../../utils/relativeId.js';
 import Node from '../Node.js';
 import { UNKNOWN } from '../values.js';
 
+const validProp = /^[a-zA-Z_$][a-zA-Z_$0-9]*$/;
+
 class Keypath {
 	constructor ( node ) {
 		this.parts = [];
 
 		while ( node.type === 'MemberExpression' ) {
-			this.parts.unshift( node.property );
+			const prop = node.property;
+
+			if ( node.computed  ) {
+				if ( prop.type !== 'Literal' || typeof prop.value !== 'string' || !validProp.test( prop.value ) ) {
+					this.computed = true;
+					return;
+				}
+			}
+
+			this.parts.unshift( prop );
 			node = node.object;
 		}
 
@@ -21,21 +31,21 @@ export default class MemberExpression extends Node {
 		// if this resolves to a namespaced declaration, prepare
 		// to replace it
 		// TODO this code is a bit inefficient
-		if ( isReference( this ) ) { // TODO optimise namespace access like `foo['bar']` as well
-			const keypath = new Keypath( this );
+		const keypath = new Keypath( this );
 
+		if ( !keypath.computed ) {
 			let declaration = scope.findDeclaration( keypath.root.name );
 
 			while ( declaration.isNamespace && keypath.parts.length ) {
 				const exporterId = declaration.module.id;
 
 				const part = keypath.parts[0];
-				declaration = declaration.module.traceExport( part.name );
+				declaration = declaration.module.traceExport( part.name || part.value );
 
 				if ( !declaration ) {
 					this.module.warn({
 						code: 'MISSING_EXPORT',
-						message: `'${part.name}' is not exported by '${relativeId( exporterId )}'`,
+						message: `'${part.name || part.value}' is not exported by '${relativeId( exporterId )}'`,
 						url: `https://github.com/rollup/rollup/wiki/Troubleshooting#name-is-not-exported-by-module`
 					}, part.start );
 					this.replacement = 'undefined';

test/form/namespace-optimization-computed-string/_config.js

@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'it does dynamic lookup optimization of internal namespaces for string-literal keys'
+};

test/form/namespace-optimization-computed-string/_expected/amd.js

@@ -0,0 +1,7 @@
+define(function () { 'use strict';
+
+	function a () {}
+
+	a();
+
+});

test/form/namespace-optimization-computed-string/_expected/cjs.js

@@ -0,0 +1,5 @@
+'use strict';
+
+function a () {}
+
+a();

test/form/namespace-optimization-computed-string/_expected/es.js

@@ -0,0 +1,3 @@
+function a () {}
+
+a();

test/form/namespace-optimization-computed-string/_expected/iife.js

@@ -0,0 +1,8 @@
+(function () {
+	'use strict';
+
+	function a () {}
+
+	a();
+
+}());

test/form/namespace-optimization-computed-string/_expected/umd.js

@@ -0,0 +1,11 @@
+(function (global, factory) {
+	typeof exports === 'object' && typeof module !== 'undefined' ? factory() :
+	typeof define === 'function' && define.amd ? define(factory) :
+	(factory());
+}(this, (function () { 'use strict';
+
+	function a () {}
+
+	a();
+
+})));

test/form/namespace-optimization-computed-string/bar.js

@@ -0,0 +1,3 @@
+import * as quux from './quux.js';
+
+export { quux };

test/form/namespace-optimization-computed-string/foo.js

@@ -0,0 +1,3 @@
+import * as bar from './bar.js';
+
+export { bar };

test/form/namespace-optimization-computed-string/main.js

@@ -0,0 +1,3 @@
+import * as foo from './foo.js';
+
+foo['bar']['quux']['a']();

test/form/namespace-optimization-computed-string/quux.js

@@ -0,0 +1 @@
+export function a () {}