put Object.freeze fallback behind legacy option

src/Bundle.js

@@ -95,6 +95,7 @@ export default class Bundle {
 		this.onwarn = options.onwarn || makeOnwarn();
 
 		this.varOrConst = options.preferConst ? 'const' : 'var';
+		this.legacy = options.legacy;
 		this.acornOptions = options.acorn || {};
 
 		this.dependentExpressions = [];
@@ -370,7 +371,7 @@ export default class Bundle {
 		timeStart( 'render modules' );
 
 		this.orderedModules.forEach( module => {
-			const source = module.render( format === 'es' );
+			const source = module.render( format === 'es', this.legacy );
 
 			if ( source.toString().length ) {
 				magicString.addSource( source );

src/Declaration.js

@@ -75,7 +75,7 @@ export class SyntheticNamespaceDeclaration {
 		return this.name;
 	}
 
-	renderBlock ( es, indentString ) {
+	renderBlock ( es, legacy, indentString ) {
 		const members = keys( this.originals ).map( name => {
 			const original = this.originals[ name ];
 
@@ -86,7 +86,8 @@ export class SyntheticNamespaceDeclaration {
 			return `${indentString}${name}: ${original.getName( es )}`;
 		});
 
-		return `${this.module.bundle.varOrConst} ${this.getName( es )} = (Object.freeze || Object)({\n${members.join( ',\n' )}\n});\n\n`;
+		const callee = legacy ? `(Object.freeze || Object)` : `Object.freeze`;
+		return `${this.module.bundle.varOrConst} ${this.getName( es )} = ${callee}({\n${members.join( ',\n' )}\n});\n\n`;
 	}
 }
 

src/Module.js

@@ -309,7 +309,7 @@ export default class Module {
 		return this.declarations['*'];
 	}
 
-	render ( es ) {
+	render ( es, legacy ) {
 		const magicString = this.magicString.clone();
 
 		for ( const node of this.ast.body ) {
@@ -317,7 +317,7 @@ export default class Module {
 		}
 
 		if ( this.namespace().needsNamespaceBlock ) {
-			magicString.append( '\n\n' + this.namespace().renderBlock( es, '\t' ) ); // TODO use correct indentation
+			magicString.append( '\n\n' + this.namespace().renderBlock( es, legacy, '\t' ) ); // TODO use correct indentation
 		}
 
 		return magicString.trim();

src/rollup.js

@@ -24,6 +24,7 @@ const ALLOWED_KEYS = [
 	'indent',
 	'interop',
 	'intro',
+	'legacy',
 	'moduleContext',
 	'moduleId',
 	'moduleName',

test/form/legacy/_config.js

@@ -0,0 +1,6 @@
+module.exports = {
+	description: 'supports environments without Object.freeze',
+	options: {
+		legacy: true
+	}
+};

test/form/legacy/_expected/amd.js

@@ -0,0 +1,13 @@
+define(function () { 'use strict';
+
+	const foo = 42;
+
+
+	var namespace = (Object.freeze || Object)({
+		foo: foo
+	});
+
+	const x = 'foo';
+	assert.equal( namespace[x], 42 );
+
+});

test/form/legacy/_expected/cjs.js

@@ -0,0 +1,11 @@
+'use strict';
+
+const foo = 42;
+
+
+var namespace = (Object.freeze || Object)({
+	foo: foo
+});
+
+const x = 'foo';
+assert.equal( namespace[x], 42 );

test/form/legacy/_expected/es.js

@@ -0,0 +1,9 @@
+const foo = 42;
+
+
+var namespace = (Object.freeze || Object)({
+	foo: foo
+});
+
+const x = 'foo';
+assert.equal( namespace[x], 42 );

test/form/legacy/_expected/iife.js

@@ -0,0 +1,14 @@
+(function () {
+	'use strict';
+
+	const foo = 42;
+
+
+	var namespace = (Object.freeze || Object)({
+		foo: foo
+	});
+
+	const x = 'foo';
+	assert.equal( namespace[x], 42 );
+
+}());

test/form/legacy/_expected/umd.js

@@ -0,0 +1,17 @@
+(function (global, factory) {
+	typeof exports === 'object' && typeof module !== 'undefined' ? factory() :
+	typeof define === 'function' && define.amd ? define(factory) :
+	(factory());
+}(this, (function () { 'use strict';
+
+	const foo = 42;
+
+
+	var namespace = (Object.freeze || Object)({
+		foo: foo
+	});
+
+	const x = 'foo';
+	assert.equal( namespace[x], 42 );
+
+})));

test/form/legacy/main.js

@@ -0,0 +1,4 @@
+import * as namespace from './namespace.js';
+
+const x = 'foo';
+assert.equal( namespace[x], 42 );

test/form/legacy/namespace.js

@@ -0,0 +1 @@
+export const foo = 42;

test/form/prefer-const/_expected/amd.js

@@ -4,7 +4,7 @@ define(['external', 'other', 'another'], function (external, other, another) { '
 	const b = 2;
 
 
-	const namespace = (Object.freeze || Object)({
+	const namespace = Object.freeze({
 		a: a,
 		b: b
 	});

test/form/prefer-const/_expected/cjs.js

@@ -8,7 +8,7 @@ const a = 1;
 const b = 2;
 
 
-const namespace = (Object.freeze || Object)({
+const namespace = Object.freeze({
 	a: a,
 	b: b
 });

test/form/prefer-const/_expected/es.js

@@ -6,7 +6,7 @@ const a = 1;
 const b = 2;
 
 
-const namespace = (Object.freeze || Object)({
+const namespace = Object.freeze({
 	a: a,
 	b: b
 });

test/form/prefer-const/_expected/iife.js

@@ -5,7 +5,7 @@ const myBundle = (function (external,other,another) {
 	const b = 2;
 
 
-	const namespace = (Object.freeze || Object)({
+	const namespace = Object.freeze({
 		a: a,
 		b: b
 	});

test/form/prefer-const/_expected/umd.js

@@ -8,7 +8,7 @@
 	const b = 2;
 
 
-	const namespace = (Object.freeze || Object)({
+	const namespace = Object.freeze({
 		a: a,
 		b: b
 	});

test/test.js

@@ -90,7 +90,7 @@ describe( 'rollup', function () {
 			return rollup.rollup({ entry: 'x', plUgins: [] }).then( () => {
 				throw new Error( 'Missing expected error' );
 			}, err => {
-				assert.equal( err.message, 'Unexpected key \'plUgins\' found, expected one of: acorn, banner, cache, context, dest, entry, exports, external, footer, format, globals, indent, interop, intro, moduleContext, moduleId, moduleName, noConflict, onwarn, outro, paths, plugins, preferConst, sourceMap, sourceMapFile, targets, treeshake, useStrict' );
+				assert.equal( err.message, 'Unexpected key \'plUgins\' found, expected one of: acorn, banner, cache, context, dest, entry, exports, external, footer, format, globals, indent, interop, intro, legacy, moduleContext, moduleId, moduleName, noConflict, onwarn, outro, paths, plugins, preferConst, sourceMap, sourceMapFile, targets, treeshake, useStrict' );
 			});
 		});