support default exports from bundle

src/Bundle.js

@@ -1,4 +1,4 @@
-import { resolve } from 'path';
+import { basename, extname, resolve } from 'path';
 import { readFile } from 'sander';
 import MagicString from 'magic-string';
 import { keys, has } from './utils/object';
@@ -10,9 +10,13 @@ import replaceIdentifiers from './utils/replaceIdentifiers';
 import makeLegalIdentifier from './utils/makeLegalIdentifier';
 import { defaultResolver } from './utils/resolvePath';
 
+function badExports ( option, keys ) {
+	throw new Error( `'${option}' was specified for options.exports, but entry module has following exports: ${keys.join(', ')}` );
+}
+
 export default class Bundle {
 	constructor ( options ) {
-		this.base = options.base || process.cwd();
+		this.base = resolve( options.base || process.cwd() );
 		this.entryPath = resolve( this.base, options.entry ).replace( /\.js$/, '' ) + '.js';
 		this.resolvePath = options.resolvePath || defaultResolver;
 
@@ -20,6 +24,7 @@ export default class Bundle {
 		this.modulePromises = {};
 		this.statements = [];
 		this.externalModules = [];
+		this.defaultExportName = null;
 	}
 
 	fetchModule ( importee, importer ) {
@@ -72,11 +77,29 @@ export default class Bundle {
 							// Exclude imports
 							if ( /^Import/.test( node.type ) ) return;
 
-							if ( node.type === 'ExportNamedDeclaration' ) {
+							// Exclude default exports that proxy a name
+							// e.g. `export default foo`
+							if ( node.type === 'ExportDefaultDeclaration' && /Declaration$/.test( node.declaration.type ) ) return;
+
 							// Exclude specifier exports
-								if ( node.specifiers.length ) return;
+							// e.g. `export { foo }`
+							if ( node.type === 'ExportNamedDeclaration' && node.specifiers.length ) return;
+
+							// Include everything else...
+
+							if ( node.type === 'ExportDefaultDeclaration' ) {
+								// TODO generic 'get deconflicted name' mechanism
+								let defaultExportName = makeLegalIdentifier( basename( this.entryPath ).slice( 0, -extname( this.entryPath ).length ) );
+								while ( this.entryModule.ast._scope.contains( defaultExportName ) ) {
+									defaultExportName = `_${defaultExportName}`;
+								}
+
+								this.defaultExportName = defaultExportName;
+								node._source.overwrite( node.start, node.declaration.start, `var ${defaultExportName} = ` );
+							}
 
-								// Remove the `export` from everything else
+							if ( node.type === 'ExportNamedDeclaration' ) {
+								// Remove the `export`
 								node._source.remove( node.start, node.declaration.start );
 							}
 
@@ -136,6 +159,9 @@ export default class Bundle {
 	generate ( options = {} ) {
 		let magicString = new MagicString.Bundle({ separator: '' });
 
+		// Determine export mode - 'default', 'named', 'none'
+		let exportMode = this.getExportMode( options.exports );
+
 		// Apply new names and add to the output bundle
 		this.statements.forEach( statement => {
 			let replacements = {};
@@ -162,7 +188,7 @@ export default class Bundle {
 			throw new Error( `You must specify an output type - valid options are ${keys( finalisers ).join( ', ' )}` );
 		}
 
-		magicString = finalise( this, magicString, options );
+		magicString = finalise( this, magicString, exportMode, options );
 
 		return {
 			code: magicString.toString(),
@@ -173,4 +199,32 @@ export default class Bundle {
 			})
 		};
 	}
+
+	getExportMode ( exportMode ) {
+		const exportKeys = keys( this.entryModule.exports );
+
+		if ( exportMode === 'default' ) {
+			if ( exportKeys.length !== 1 || exportKeys[0] !== 'default' ) {
+				badExports( 'default', exportKeys );
+			}
+		} else if ( exportMode === 'none' && exportKeys.length ) {
+			badExports( 'none', exportKeys );
+		}
+
+		if ( !exportMode || exportMode === 'auto' ) {
+			if ( exportKeys.length === 0 ) {
+				exportMode = 'none';
+			} else if ( exportKeys.length === 1 && exportKeys[0] === 'default' ) {
+				exportMode = 'default';
+			} else {
+				exportMode = 'named';
+			}
+		}
+
+		if ( !/(?:default|named|none)/.test( exportMode ) ) {
+			throw new Error( `options.exports must be 'default', 'named', 'none', 'auto', or left unspecified (defaults to 'auto')` );
+		}
+
+		return exportMode;
+	}
 }

src/finalisers/amd.js

@@ -1,3 +1,3 @@
-export default function amd ( bundle, magicString, options ) {
+export default function amd ( bundle, magicString, exportMode, options ) {
 	throw new Error( 'TODO' );
 }

src/finalisers/cjs.js

@@ -1,6 +1,6 @@
 import { keys } from '../utils/object';
 
-export default function cjs ( bundle, magicString ) {
+export default function cjs ( bundle, magicString, exportMode ) {
 	let intro = `'use strict';\n\n`;
 
 	// TODO handle ambiguous default imports
@@ -24,8 +24,11 @@ export default function cjs ( bundle, magicString ) {
 
 	magicString.prepend( intro );
 
-	// TODO handle default exports
-	const exportBlock = keys( bundle.entryModule.exports )
+	let exportBlock;
+	if ( exportMode === 'default' && bundle.entryModule.exports.default ) {
+		exportBlock = `module.exports = ${bundle.defaultExportName};`;
+	} else if ( exportMode === 'named' ) {
+		exportBlock = keys( bundle.entryModule.exports )
 			.map( key => {
 				const specifier = bundle.entryModule.exports[ key ];
 				const name = bundle.entryModule.getCanonicalName( specifier.localName );
@@ -33,6 +36,7 @@ export default function cjs ( bundle, magicString ) {
 				return `exports.${key} = ${name};`;
 			})
 			.join( '\n' );
+	}
 
 	if ( exportBlock ) {
 		magicString.append( '\n\n' + exportBlock );

src/finalisers/es6.js

@@ -1,3 +1,3 @@
-export default function es6 ( bundle, magicString, options ) {
+export default function es6 ( bundle, magicString, exportMode, options ) {
 	throw new Error( 'TODO' );
 }

src/finalisers/umd.js

@@ -1,4 +1,4 @@
-export default function umd ( bundle, magicString, options ) {
+export default function umd ( bundle, magicString, exportMode, options ) {
 	const indentStr = magicString.getIndentString();
 
 	const intro =

test/samples/export-default-expression/_config.js

@@ -0,0 +1,8 @@
+var assert = require( 'assert' );
+
+module.exports = {
+	description: 'exports a default value as module.exports',
+	exports: function ( exports ) {
+		assert.equal( exports, 42 );
+	}
+};

test/samples/export-default-expression/main.js

@@ -0,0 +1 @@
+export default 42;

test/test.js

@@ -30,12 +30,14 @@ describe( 'rollup', function () {
 					});
 
 					try {
-						var fn = new Function( 'require', 'exports', 'assert', result.code );
-						var exports = {};
-						fn( require, exports, assert );
+						var fn = new Function( 'require', 'module', 'exports', 'assert', result.code );
+						var module = {
+							exports: {}
+						};
+						fn( require, module, module.exports, assert );
 
 						if ( config.exports ) {
-							config.exports( exports, assert );
+							config.exports( module.exports, assert );
 						}
 					} catch ( err ) {
 						console.log( result.code );