handle bare imports (#23)

src/index.js

@@ -143,12 +143,18 @@ export default function commonjs ( options = {} ) {
 
 					if ( !existing ) {
 						name = `require$$${uid++}`;
-						required[ source ] = { source, name };
+						required[ source ] = { source, name, importsDefault: false };
 					} else {
 						name = required[ source ].name;
 					}
 
-					magicString.overwrite( node.start, node.end, name );
+					if ( parent.type !== 'ExpressionStatement' ) {
+						required[ source ].importsDefault = true;
+						magicString.overwrite( node.start, node.end, name );
+					} else {
+						// is a bare import, e.g. `require('foo');`
+						magicString.remove( parent.start, parent.end );
+					}
 				},
 
 				leave ( node ) {
@@ -170,7 +176,10 @@ export default function commonjs ( options = {} ) {
 			const name = getName( id );
 
 			const importBlock = sources.length ?
-				sources.map( source => `import ${required[ source ].name} from '${source}';` ).join( '\n' ) :
+				sources.map( source => {
+					const { name, importsDefault } = required[ source ];
+					return `import ${importsDefault ? `${name} from ` : ``}'${source}';`;
+				}).join( '\n' ) :
 				'';
 
 			const args = `module${uses.exports || uses.global ? ', exports' : ''}${uses.global ? ', global' : ''}`;

test/samples/bare-import/bar.js

@@ -0,0 +1 @@
+Math.bar = 42;

test/samples/bare-import/foo.js

@@ -0,0 +1 @@
+require( './bar.js' );

test/samples/bare-import/main.js

@@ -0,0 +1,3 @@
+import './foo.js';
+
+assert.equal( Math.bar, 42 );

test/test.js

@@ -153,6 +153,13 @@ describe( 'rollup-plugin-commonjs', () => {
 		});
 	});
 
+	it( 'handles bare imports', () => {
+		return rollup({
+			entry: 'samples/bare-import/main.js',
+			plugins: [ commonjs() ]
+		}).then( executeBundle );
+	});
+
 	it( 'does not export __esModule', () => {
 		return rollup({
 			entry: 'samples/__esModule/main.js',