handle multiple exports of a single binding

src/Bundle.js

@@ -290,35 +290,34 @@ export default class Bundle {
 		//
 		// This doesn't apply if the bundle is exported as ES6!
 		let allBundleExports = blank();
+		let varDeclarations = blank();
 		let varExports = blank();
+		let getterExports = [];
 
-		if ( format !== 'es6' && exportMode === 'named' ) {
-			keys( this.entryModule.exports ).forEach( key => {
-				const exportDeclaration = this.entryModule.exports[ key ];
-
-				const originalDeclaration = this.entryModule.findDeclaration( exportDeclaration.localName );
-
-				if ( originalDeclaration && originalDeclaration.type === 'VariableDeclaration' ) {
-					const canonicalName = this.trace( this.entryModule, exportDeclaration.localName, false );
-
-					allBundleExports[ canonicalName ] = `exports.${key}`;
-					varExports[ key ] = true;
-				}
+		this.orderedModules.forEach( module => {
+			keys( module.varDeclarations ).forEach( name => {
+				varDeclarations[ module.replacements[ name ] || name ] = true;
 			});
+		});
 
-			keys( this.entryModule.reexports ).forEach( key => {
-				const reexportDeclaration = this.entryModule.reexports[ key ];
-
-				if ( reexportDeclaration.module.isExternal ) return;
-				const originalDeclaration = reexportDeclaration.module.findDeclaration( reexportDeclaration.localName );
-
-				if ( originalDeclaration && originalDeclaration.type === 'VariableDeclaration' ) {
-					const canonicalName = this.trace( reexportDeclaration.module, reexportDeclaration.localName, false );
-
-					allBundleExports[ canonicalName ] = `exports.${key}`;
-					varExports[ key ] = true;
-				}
-			});
+		if ( format !== 'es6' && exportMode === 'named' ) {
+			keys( this.entryModule.exports )
+				.concat( keys( this.entryModule.reexports ) )
+				.forEach( name => {
+					const canonicalName = this.traceExport( this.entryModule, name );
+
+					if ( varDeclarations[ canonicalName ] ) {
+						varExports[ name ] = true;
+
+						// if the same binding is exported multiple ways, we need to
+						// use getters to keep all exports in sync
+						if ( allBundleExports[ canonicalName ] ) {
+							getterExports.push({ key: name, value: allBundleExports[ canonicalName ] });
+						} else {
+							allBundleExports[ canonicalName ] = `exports.${name}`;
+						}
+					}
+				});
 		}
 
 		// since we're rewriting variable exports, we want to
@@ -327,7 +326,6 @@ export default class Bundle {
 			.concat( keys( this.entryModule.reexports ) )
 			.filter( key => !varExports[ key ] );
 
-
 		let magicString = new MagicString.Bundle({ separator: '\n\n' });
 
 		this.orderedModules.forEach( module => {
@@ -370,6 +368,16 @@ export default class Bundle {
 
 		magicString.prepend( namespaceBlock );
 
+		if ( getterExports.length ) {
+			// TODO offer ES3-safe (but not spec-compliant) alternative?
+			const indent = magicString.getIndentString();
+			const getterExportsBlock = `Object.defineProperties(exports, {\n` +
+				getterExports.map( ({ key, value }) => indent + `${key}: { get: function () { return ${value}; } }` ).join( ',\n' ) +
+			`\n});`;
+
+			magicString.append( '\n\n' + getterExportsBlock );
+		}
+
 		const finalise = finalisers[ format ];
 
 		if ( !finalise ) {

src/Module.js

@@ -65,6 +65,7 @@ export default class Module {
 		this.replacements = blank();
 
 		this.definitions = blank();
+		this.varDeclarations = blank();
 		this.definitionPromises = blank();
 		this.modifications = blank();
 
@@ -200,6 +201,10 @@ export default class Module {
 				this.definitions[ name ] = statement;
 			});
 
+			keys( statement.declaresVar ).forEach( name => {
+				this.varDeclarations[ name ] = statement;
+			});
+
 			keys( statement.modifies ).forEach( name => {
 				( this.modifications[ name ] || ( this.modifications[ name ] = [] ) ).push( statement );
 			});
@@ -303,33 +308,6 @@ export default class Module {
 			});
 	}
 
-	findDeclaration ( localName ) {
-		const importDeclaration = this.imports[ localName ];
-
-		// name was defined by another module
-		if ( importDeclaration ) {
-			const module = importDeclaration.module;
-
-			if ( module.isExternal ) return null;
-			if ( importDeclaration.name === '*' ) return null;
-			if ( importDeclaration.name === 'default' ) return null;
-
-			const exportDeclaration = module.exports[ importDeclaration.name ];
-			return module.findDeclaration( exportDeclaration.localName );
-		}
-
-		// name was defined by this module, if any
-		let i = this.statements.length;
-		while ( i-- ) {
-			const declaration = this.statements[i].scope.declarations[ localName ];
-			if ( declaration ) {
-				return declaration;
-			}
-		}
-
-		return null;
-	}
-
 	mark ( name ) {
 		// shortcut cycles
 		if ( this.definitionPromises[ name ] ) {

src/Statement.js

@@ -18,6 +18,7 @@ export default class Statement {
 
 		this.scope = new Scope();
 		this.defines = blank();
+		this.declaresVar = blank();
 		this.modifies = blank();
 		this.dependsOn = blank();
 		this.stronglyDependsOn = blank();
@@ -43,7 +44,7 @@ export default class Statement {
 					case 'FunctionDeclaration':
 					case 'ArrowFunctionExpression':
 						if ( node.type === 'FunctionDeclaration' ) {
-							scope.addDeclaration( node.id.name, node );
+							scope.addDeclaration( node.id.name, node, false );
 						}
 
 						newScope = new Scope({
@@ -55,7 +56,7 @@ export default class Statement {
 						// named function expressions - the name is considered
 						// part of the function's scope
 						if ( node.type === 'FunctionExpression' && node.id ) {
-							newScope.addDeclaration( node.id.name, node );
+							newScope.addDeclaration( node.id.name, node, false );
 						}
 
 						break;
@@ -81,12 +82,12 @@ export default class Statement {
 
 					case 'VariableDeclaration':
 						node.declarations.forEach( declarator => {
-							scope.addDeclaration( declarator.id.name, node );
+							scope.addDeclaration( declarator.id.name, node, true );
 						});
 						break;
 
 					case 'ClassDeclaration':
-						scope.addDeclaration( node.id.name, node );
+						scope.addDeclaration( node.id.name, node, false );
 						break;
 				}
 
@@ -142,6 +143,10 @@ export default class Statement {
 		keys( scope.declarations ).forEach( name => {
 			this.defines[ name ] = true;
 		});
+
+		keys( scope.varDeclarations ).forEach( name => {
+			this.declaresVar[ name ] = true;
+		});
 	}
 
 	checkForReads ( scope, node, parent, strong ) {

src/ast/Scope.js

@@ -12,6 +12,7 @@ export default class Scope {
 		this.parent = options.parent;
 		this.depth = this.parent ? this.parent.depth + 1 : 0;
 		this.declarations = blank();
+		this.varDeclarations = blank();
 		this.isBlockScope = !!options.block;
 
 		if ( options.params ) {
@@ -21,25 +22,16 @@ export default class Scope {
 		}
 	}
 
-	// add ( name, isBlockDeclaration ) {
-	// 	if ( !isBlockDeclaration && this.isBlockScope ) {
-	// 		// it's a `var` or function declaration, and this
-	// 		// is a block scope, so we need to go up
-	// 		this.parent.add( name, isBlockDeclaration );
-	// 	} else {
-	// 		this.names.push( name );
-	// 	}
-	// }
-
-	addDeclaration ( name, declaration ) {
+	addDeclaration ( name, declaration, isVar ) {
 		const isBlockDeclaration = declaration.type === 'VariableDeclaration' && blockDeclarations[ declaration.kind ];
 
 		if ( !isBlockDeclaration && this.isBlockScope ) {
 			// it's a `var` or function declaration, and this
 			// is a block scope, so we need to go up
-			this.parent.addDeclaration( name, declaration );
+			this.parent.addDeclaration( name, declaration, isVar );
 		} else {
 			this.declarations[ name ] = declaration;
+			if ( isVar ) this.varDeclarations[ name ] = true;
 		}
 	}
 

test/function/export-two-ways/_config.js

@@ -0,0 +1,10 @@
+var assert = require( 'assert' );
+
+module.exports = {
+	description: 'exports the same binding more than one way',
+	exports: function ( exports ) {
+		assert.equal( exports.a, 2 );
+		assert.equal( exports.b, 2 );
+		assert.equal( exports.c, 2 );
+	}
+};

test/function/export-two-ways/foo.js

@@ -0,0 +1,2 @@
+export var foo = 1;
+foo = 2;

test/function/export-two-ways/main.js

@@ -0,0 +1,5 @@
+import { foo } from './foo';
+
+export { foo as a };
+export { foo as b };
+export { foo as c };