From e85626ea02836d753e97ae3ee3dceeb0d2e0d650 Mon Sep 17 00:00:00 2001
From: Rich-Harris <richard.a.harris@gmail.com>
Date: Sun, 5 Jun 2016 12:10:55 -0400
Subject: [PATCH] options.preferConst to use const instead of var when creating
 statements (#653)

---
 src/Bundle.js                            |  2 ++
 src/Declaration.js                       |  2 +-
 src/Module.js                            |  2 +-
 src/finalisers/cjs.js                    | 10 ++++++----
 src/finalisers/iife.js                   |  2 +-
 src/finalisers/shared/getInteropBlock.js |  2 +-
 src/rollup.js                            |  1 +
 test/form/prefer-const/_config.js        |  7 +++++++
 test/form/prefer-const/_expected/amd.js  | 18 ++++++++++++++++++
 test/form/prefer-const/_expected/cjs.js  | 20 ++++++++++++++++++++
 test/form/prefer-const/_expected/es6.js  | 18 ++++++++++++++++++
 test/form/prefer-const/_expected/iife.js | 19 +++++++++++++++++++
 test/form/prefer-const/_expected/umd.js  | 22 ++++++++++++++++++++++
 test/form/prefer-const/main.js           |  9 +++++++++
 test/form/prefer-const/namespace.js      |  2 ++
 test/test.js                             |  2 +-
 16 files changed, 129 insertions(+), 9 deletions(-)
 create mode 100644 test/form/prefer-const/_config.js
 create mode 100644 test/form/prefer-const/_expected/amd.js
 create mode 100644 test/form/prefer-const/_expected/cjs.js
 create mode 100644 test/form/prefer-const/_expected/es6.js
 create mode 100644 test/form/prefer-const/_expected/iife.js
 create mode 100644 test/form/prefer-const/_expected/umd.js
 create mode 100644 test/form/prefer-const/main.js
 create mode 100644 test/form/prefer-const/namespace.js

diff --git a/src/Bundle.js b/src/Bundle.js
index fb160c0..95c0d10 100644
--- a/src/Bundle.js
+++ b/src/Bundle.js
@@ -73,6 +73,8 @@ export default class Bundle {
 
 		// TODO strictly speaking, this only applies with non-ES6, non-default-only bundles
 		[ 'module', 'exports', '_interopDefault' ].forEach( global => this.assumedGlobals[ global ] = true );
+
+		this.varOrConst = options.preferConst ? 'const' : 'var';
 	}
 
 	build () {
diff --git a/src/Declaration.js b/src/Declaration.js
index 0c8fd1e..a8e192a 100644
--- a/src/Declaration.js
+++ b/src/Declaration.js
@@ -241,7 +241,7 @@ export class SyntheticNamespaceDeclaration {
 			return `${indentString}${name}: ${original.render()}`;
 		});
 
-		return `var ${this.render()} = Object.freeze({\n${members.join( ',\n' )}\n});\n\n`;
+		return `${this.module.bundle.varOrConst} ${this.render()} = Object.freeze({\n${members.join( ',\n' )}\n});\n\n`;
 	}
 
 	render () {
diff --git a/src/Module.js b/src/Module.js
index 4f68ab7..175ecd5 100644
--- a/src/Module.js
+++ b/src/Module.js
@@ -592,7 +592,7 @@ export default class Module {
 					if ( statement.node.declaration.type === 'FunctionExpression' ) {
 						magicString.overwrite( statement.node.start, statement.node.declaration.start + 8, `function ${defaultName}` );
 					} else {
-						magicString.overwrite( statement.node.start, statement.node.declaration.start, `var ${defaultName} = ` );
+						magicString.overwrite( statement.node.start, statement.node.declaration.start, `${this.bundle.varOrConst} ${defaultName} = ` );
 					}
 				}
 
diff --git a/src/finalisers/cjs.js b/src/finalisers/cjs.js
index 07adf72..b921429 100644
--- a/src/finalisers/cjs.js
+++ b/src/finalisers/cjs.js
@@ -9,18 +9,20 @@ export default function cjs ( bundle, magicString, { exportMode }, options ) {
 		intro += `function _interopDefault (ex) { return (ex && (typeof ex === 'object') && 'default' in ex) ? ex['default'] : ex; }\n\n`;
 	}
 
+	const varOrConst = bundle.varOrConst;
+
 	// TODO handle empty imports, once they're supported
 	const importBlock = bundle.externalModules
 		.map( module => {
 			if ( module.declarations.default ) {
 				if (module.exportsNames) {
-					return `var ${module.name} = require('${module.id}');` +
-						`\nvar ${module.name}__default = _interopDefault(${module.name});`;
+					return `${varOrConst} ${module.name} = require('${module.id}');` +
+						`\n${varOrConst} ${module.name}__default = _interopDefault(${module.name});`;
 				} else {
-					return `var ${module.name} = _interopDefault(require('${module.id}'));`;
+					return `${varOrConst} ${module.name} = _interopDefault(require('${module.id}'));`;
 				}
 			} else {
-				return `var ${module.name} = require('${module.id}');`;
+				return `${varOrConst} ${module.name} = require('${module.id}');`;
 			}
 		})
 		.join( '\n' );
diff --git a/src/finalisers/iife.js b/src/finalisers/iife.js
index 1d4dfb2..adb7019 100644
--- a/src/finalisers/iife.js
+++ b/src/finalisers/iife.js
@@ -41,7 +41,7 @@ export default function iife ( bundle, magicString, { exportMode, indentString }
 	let outro = `\n\n}(${dependencies}));`;
 
 	if ( exportMode === 'default' ) {
-		intro = ( isNamespaced ? `this.` : `var ` ) + `${name} = ${intro}`;
+		intro = ( isNamespaced ? `this.` : `${bundle.varOrConst} ` ) + `${name} = ${intro}`;
 	}
 
 	if ( isNamespaced ) {
diff --git a/src/finalisers/shared/getInteropBlock.js b/src/finalisers/shared/getInteropBlock.js
index e0e2617..a747d82 100644
--- a/src/finalisers/shared/getInteropBlock.js
+++ b/src/finalisers/shared/getInteropBlock.js
@@ -3,7 +3,7 @@ export default function getInteropBlock ( bundle ) {
 		.map( module => {
 			return module.declarations.default ?
 				( module.exportsNames ?
-					`var ${module.name}__default = 'default' in ${module.name} ? ${module.name}['default'] : ${module.name};` :
+					`${bundle.varOrConst} ${module.name}__default = 'default' in ${module.name} ? ${module.name}['default'] : ${module.name};` :
 					`${module.name} = 'default' in ${module.name} ? ${module.name}['default'] : ${module.name};` ) :
 				null;
 		})
diff --git a/src/rollup.js b/src/rollup.js
index 490fe72..77a97bd 100644
--- a/src/rollup.js
+++ b/src/rollup.js
@@ -25,6 +25,7 @@ const ALLOWED_KEYS = [
 	'onwarn',
 	'outro',
 	'plugins',
+	'preferConst',
 	'sourceMap',
 	'treeshake',
 	'useStrict'
diff --git a/test/form/prefer-const/_config.js b/test/form/prefer-const/_config.js
new file mode 100644
index 0000000..ebb4828
--- /dev/null
+++ b/test/form/prefer-const/_config.js
@@ -0,0 +1,7 @@
+module.exports = {
+	description: 'uses const instead of var if specified (#653)',
+	options: {
+		preferConst: true,
+		moduleName: 'myBundle'
+	}
+};
diff --git a/test/form/prefer-const/_expected/amd.js b/test/form/prefer-const/_expected/amd.js
new file mode 100644
index 0000000..a89dacd
--- /dev/null
+++ b/test/form/prefer-const/_expected/amd.js
@@ -0,0 +1,18 @@
+define(['external', 'other', 'another'], function (external, other, another) { 'use strict';
+
+	const a = 1;
+	const b = 2;
+
+
+	const namespace = Object.freeze({
+		a: a,
+		b: b
+	});
+
+	console.log( Object.keys( namespace ) );
+
+	const main = 42;
+
+	return main;
+
+});
diff --git a/test/form/prefer-const/_expected/cjs.js b/test/form/prefer-const/_expected/cjs.js
new file mode 100644
index 0000000..5c2e4da
--- /dev/null
+++ b/test/form/prefer-const/_expected/cjs.js
@@ -0,0 +1,20 @@
+'use strict';
+
+const external = require('external');
+const other = require('other');
+const another = require('another');
+
+const a = 1;
+const b = 2;
+
+
+const namespace = Object.freeze({
+	a: a,
+	b: b
+});
+
+console.log( Object.keys( namespace ) );
+
+const main = 42;
+
+module.exports = main;
diff --git a/test/form/prefer-const/_expected/es6.js b/test/form/prefer-const/_expected/es6.js
new file mode 100644
index 0000000..8f5a5c9
--- /dev/null
+++ b/test/form/prefer-const/_expected/es6.js
@@ -0,0 +1,18 @@
+import 'external';
+import 'other';
+import 'another';
+
+const a = 1;
+const b = 2;
+
+
+const namespace = Object.freeze({
+	a: a,
+	b: b
+});
+
+console.log( Object.keys( namespace ) );
+
+const main = 42;
+
+export default main;
diff --git a/test/form/prefer-const/_expected/iife.js b/test/form/prefer-const/_expected/iife.js
new file mode 100644
index 0000000..9c66729
--- /dev/null
+++ b/test/form/prefer-const/_expected/iife.js
@@ -0,0 +1,19 @@
+const myBundle = (function (external,other,another) {
+	'use strict';
+
+	const a = 1;
+	const b = 2;
+
+
+	const namespace = Object.freeze({
+		a: a,
+		b: b
+	});
+
+	console.log( Object.keys( namespace ) );
+
+	const main = 42;
+
+	return main;
+
+}(external,other,another));
diff --git a/test/form/prefer-const/_expected/umd.js b/test/form/prefer-const/_expected/umd.js
new file mode 100644
index 0000000..0c54878
--- /dev/null
+++ b/test/form/prefer-const/_expected/umd.js
@@ -0,0 +1,22 @@
+(function (global, factory) {
+	typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory(require('external'), require('other'), require('another')) :
+	typeof define === 'function' && define.amd ? define(['external', 'other', 'another'], factory) :
+	(global.myBundle = factory(global.external,global.other,global.another));
+}(this, function (external,other,another) { 'use strict';
+
+	const a = 1;
+	const b = 2;
+
+
+	const namespace = Object.freeze({
+		a: a,
+		b: b
+	});
+
+	console.log( Object.keys( namespace ) );
+
+	const main = 42;
+
+	return main;
+
+}));
diff --git a/test/form/prefer-const/main.js b/test/form/prefer-const/main.js
new file mode 100644
index 0000000..e8cc563
--- /dev/null
+++ b/test/form/prefer-const/main.js
@@ -0,0 +1,9 @@
+import external from 'external';
+import a from 'other';
+import { b } from 'other';
+import { another } from 'another';
+import * as namespace from './namespace.js';
+
+console.log( Object.keys( namespace ) );
+
+export default 42;
diff --git a/test/form/prefer-const/namespace.js b/test/form/prefer-const/namespace.js
new file mode 100644
index 0000000..72ab60e
--- /dev/null
+++ b/test/form/prefer-const/namespace.js
@@ -0,0 +1,2 @@
+export const a = 1;
+export const b = 2;
diff --git a/test/test.js b/test/test.js
index 22d4bce..22239fe 100644
--- a/test/test.js
+++ b/test/test.js
@@ -76,7 +76,7 @@ describe( 'rollup', function () {
 			return rollup.rollup({ entry: 'x', plUgins: [] }).then( function () {
 				throw new Error( 'Missing expected error' );
 			}, function ( err ) {
-				assert.equal( err.message, 'Unexpected key \'plUgins\' found, expected one of: banner, dest, entry, exports, external, footer, format, globals, indent, intro, moduleId, moduleName, noConflict, onwarn, outro, plugins, sourceMap, treeshake, useStrict' );
+				assert.equal( err.message, 'Unexpected key \'plUgins\' found, expected one of: banner, dest, entry, exports, external, footer, format, globals, indent, intro, moduleId, moduleName, noConflict, onwarn, outro, plugins, preferConst, sourceMap, treeshake, useStrict' );
 			});
 		});
 	});