prevent false positive with namedExports (#36)

src/index.js

@@ -186,7 +186,7 @@ export default function commonjs ( options = {} ) {
 			const sources = Object.keys( required );
 
 			if ( !sources.length && !uses.module && !uses.exports && !uses.global ) {
-				if ( Object.keys( customNamedExports ).length ) {
+				if ( Object.keys( namedExports ).length ) {
 					throw new Error( `Custom named exports were specified for ${id} but it does not appear to be a CommonJS module` );
 				}
 				return null; // not a CommonJS module

test/samples/custom-named-exports-false-positive/main.js

@@ -0,0 +1,2 @@
+import { thing } from './other.js';
+assert.equal( thing, 'yes' );

test/samples/custom-named-exports-false-positive/other.js

@@ -0,0 +1,2 @@
+/* require (https://github.com/rollup/rollup-plugin-commonjs/issues/36) */
+export const thing = 'yes';

test/test.js

@@ -193,6 +193,20 @@ describe( 'rollup-plugin-commonjs', () => {
 		}).then( executeBundle );
 	});
 
+	it( 'ignores false positives with namedExports (#36)', () => {
+		return rollup({
+			entry: 'samples/custom-named-exports-false-positive/main.js',
+			plugins: [
+				npm({ main: true }),
+				commonjs({
+					namedExports: {
+						'irrelevant': [ 'lol' ]
+					}
+				})
+			]
+		}).then( executeBundle );
+	});
+
 	it( 'converts a CommonJS module with custom file extension', () => {
 		return rollup({
 			entry: 'samples/extension/main.coffee',