Added tests for Scope, stricter .eslintrc, and contributors.

.babelrc

@@ -5,6 +5,7 @@
 		"es6.classes",
 		"es6.constants",
 		"es6.destructuring",
+		"es6.modules",
 		"es6.parameters",
 		"es6.properties.shorthand",
 		"es6.spread",

.eslintrc

@@ -1,15 +1,19 @@
 {
 	"rules": {
-		"indent": [ 2, "tab", { "SwitchCase": 1}],
+		"indent": [ 2, "tab", { "SwitchCase": 1 } ],
 		"quotes": [ 2, "single" ],
 		"linebreak-style": [ 2, "unix" ],
 		"semi": [ 2, "always" ],
+    "space-after-keywords": [ 2, "always" ],
+    "space-before-blocks": [ 2, "always" ],
+    "space-before-function-paren": [ 2, "always" ],
 		"no-mixed-spaces-and-tabs": [ 2, "smart-tabs" ],
 		"no-cond-assign": [ 0 ]
 	},
 	"env": {
 		"es6": true,
 		"browser": true,
+		"mocha": true,
 		"node": true
 	},
 	"extends": "eslint:recommended",

package.json

@@ -26,12 +26,16 @@
     "optimizer"
   ],
   "author": "Rich Harris",
+  "contributors": [
+    "Oskar Segersvärd <victorystick@gmail.com>"
+  ],
   "license": "MIT",
   "bugs": {
     "url": "https://github.com/rich-harris/rollup/issues"
   },
   "homepage": "https://github.com/rich-harris/rollup",
   "devDependencies": {
+    "babel": "^5.8.21",
     "babel-core": "^5.5.8",
     "console-group": "^0.1.2",
     "eslint": "^1.1.0",

src/Scope.js

@@ -1,43 +1,54 @@
-import { blank } from './utils/object';
+import { blank, keys } from './utils/object';
 
-class Identifier {
-	constructor ( name ) {
-		this.originalName = this.name = name;
-	}
+// A minimal `Identifier` implementation. Anything that has an `originalName`,
+// and a mutable `name` property can be used as an `Identifier`.
+function Identifier ( name ) {
+	this.originalName = this.name = name;
 }
 
-class Reference {
-	constructor ( scope, index ) {
-		this.scope = scope;
-		this.index = index;
-	}
+// A reference to an `Identifier`.
+function Reference ( scope, index ) {
+	this.scope = scope;
+	this.index = index;
+}
 
-	deref () {
-		return this.scope.ids[ this.index ];
-	}
+// Dereferences a `Reference`.
+function dereference ( ref ) {
+	return ref.scope.ids[ ref.index ];
 }
 
 function isntReference ( id ) {
 	return !( id instanceof Reference );
 }
 
-// Prefix the argument with _.
+// Prefix the argument with '_'.
 function underscorePrefix ( x ) {
 	return '_' + x;
 }
 
+// A Scope is a mapping from name to identifiers.
 export default class Scope {
 	constructor () {
 		this.ids = [];
-		this.names = {};
+		this.names = blank();
+
+		this.used = blank();
 	}
 
+	// Binds the `name` to the given reference `ref`.
 	bind ( name, ref ) {
+		if ( isntReference( ref ) ) {
+			throw new TypeError( `` );
+		}
+
 		this.ids[ this.index( name ) ] = ref;
 	}
 
+	// Deconflict all names within the scope,
+	// using the given renaming function.
+	// If no function is supplied, the name is simply prefixed with '_'.
 	deconflict ( rename = underscorePrefix ) {
-		const names = blank();
+		const names = this.used;
 
 		this.ids.filter( isntReference ).forEach( id => {
 			let name = id.name;
@@ -45,34 +56,61 @@ export default class Scope {
 			while ( name in names && names[ name ] !== id ) {
 				name = rename( name );
 			}
+			names[ name ] = id;
 
 			id.name = name;
 		});
 	}
 
-	define ( name, id ) {
-		this.ids[ this.index( name ) ] = id || new Identifier( name );
+	// Defines `name` in the scope. `name` must be a `string` or an `Identifier`.
+	define ( name ) {
+		if ( typeof name === 'string' ) {
+			this.ids[ this.index( name ) ] = new Identifier( name );
+		} else {
+			this.ids[ this.index( name.name ) ] = name;
+		}
 	}
 
+	// !! private, don't use !!
+	//
+	// Lookup the `ids` index of `name`.
 	index ( name ) {
 		if ( !( name in this.names ) ) {
-			return this.names[ name ] = 1 + this.ids.push();
+			// The `undefined` value of this push is a placeholder
+			// that should be overwritten by the caller.
+			return this.names[ name ] = this.ids.push();
 		}
 
 		return this.names[ name ];
 	}
 
+	// Lookup the identifier referred to by `name`.
 	lookup ( name ) {
 		let id = this.ids[ this.names[ name ] ];
 
 		while ( id instanceof Reference ) {
-			id = id.deref();
+			id = dereference( id );
 		}
 
 		return id;
 	}
 
+	// Get a reference to the identifier `name` in this scope.
 	reference ( name ) {
 		return new Reference( this, this.names[ name ] );
 	}
+
+	// Return the names currently in use in the scope.
+	// Names aren't considered used until they're deconflicted.
+	usedNames () {
+		return keys( this.used ).sort();
+	}
+
+	// Create and return a virtual scope, bound to
+	// the actual scope of this Scope.
+	virtual () {
+		const scope = new Scope();
+		scope.ids = this.ids;
+		return scope;
+	}
 }

test/testScope.js

@@ -0,0 +1,74 @@
+require('babel/register');
+var assert = require( 'assert' );
+
+var Scope = require( '../src/Scope' );
+
+describe( 'Scope', function () {
+	it( 'can define and bind names', function () {
+		const scope = new Scope();
+
+		// If I define 'a'...
+		scope.define( 'a' );
+
+		// ... and bind 'b' to a reference to 'a'...
+		scope.bind( 'b', scope.reference( 'a' ) );
+
+		// ... lookups for 'a' and 'b' should both
+		// resolve to the same identifier.
+		assert.equal( scope.lookup( 'b' ), scope.lookup( 'a' ) );
+	});
+
+	describe( 'virtual scope:', function () {
+		var real, a, b;
+
+		beforeEach(function () {
+			real = new Scope();
+			a = real.virtual();
+			b = real.virtual();
+		});
+
+		it( 'is created within another scope', function () {
+			// The actual ids are the same.
+			assert.equal( real.ids, a.ids );
+			assert.equal( real.ids, b.ids );
+		});
+
+		it( 'lookups different identifiers', function () {
+			// If I define 'a' in both scopes...
+			a.define( 'a' );
+			b.define( 'a' );
+
+			// ... the name 'a' should lookup different identifiers.
+			assert.notEqual( a.lookup( 'a' ), b.lookup( 'b' ) );
+		});
+
+		it( 'can deconflict names', function () {
+			a.define( 'a' );
+			b.define( 'a' );
+
+			// Deconflicting the actual scope should make all identifiers unique.
+			real.deconflict();
+
+			assert.deepEqual( real.usedNames(), [ '_a', 'a' ] );
+		});
+
+		it( 'deconflicts with a custom function, if provided', function () {
+			for (var i = 0; i < 26; i++) {
+				// Create 26 scopes, all of which define 'a'.
+				real.virtual().define( 'a' );
+			}
+
+			// Custom deconfliction function which ignores the current name.
+			var num = 10;
+			real.deconflict( function () {
+				return (num++).toString(36);
+			});
+
+			assert.deepEqual( real.usedNames(), 'abcdefghijklmnopqrstuvwxyz'.split('') );
+
+			// Deconflicting twice has no additional effect.
+			real.deconflict();
+			assert.deepEqual( real.usedNames(), 'abcdefghijklmnopqrstuvwxyz'.split('') );
+		});
+	});
+});