Make multiArgs option apply on rejections too (#35)

index.js

@@ -11,16 +11,21 @@ const processFn = (fn, opts) => function () {
 
 	return new P((resolve, reject) => {
 		args.push(function (err, result) {
-			if (err) {
-				reject(err);
-			} else if (opts.multiArgs) {
+			if (opts.multiArgs) {
 				const results = new Array(arguments.length - 1);
 
 				for (let i = 1; i < arguments.length; i++) {
 					results[i - 1] = arguments[i];
 				}
 
-				resolve(results);
+				if (err) {
+					results.unshift(err);
+					reject(results);
+				} else {
+					resolve(results);
+				}
+			} else if (err) {
+				reject(err);
 			} else {
 				resolve(result);
 			}

test.js

@@ -4,6 +4,7 @@ import pinkiePromise from 'pinkie-promise';
 import fn from './';
 
 const fixture = cb => setImmediate(() => cb(null, 'unicorn'));
+const fixture1 = cb => setImmediate(() => cb('error', 'unicorn', 'rainbow'));
 const fixture2 = (x, cb) => setImmediate(() => cb(null, x));
 const fixture3 = cb => setImmediate(() => cb(null, 'unicorn', 'rainbow'));
 const fixture4 = cb => setImmediate(() => {
@@ -30,6 +31,10 @@ test('main', async t => {
 	t.is(await fn(fixture)(), 'unicorn');
 });
 
+test('error', async t => {
+	t.is(await fn(fixture1)().catch(err => err), 'error');
+});
+
 test('pass argument', async t => {
 	t.is(await fn(fixture2)('rainbow'), 'rainbow');
 });
@@ -42,6 +47,10 @@ test('multiArgs option', async t => {
 	t.deepEqual(await fn(fixture3, {multiArgs: true})(), ['unicorn', 'rainbow']);
 });
 
+test('multiArgs option — rejection', async t => {
+	t.deepEqual(await fn(fixture1, {multiArgs: true})().catch(err => err), ['error', 'unicorn', 'rainbow']);
+});
+
 test('wrap core method', async t => {
 	t.is(JSON.parse(await fn(fs.readFile)('package.json')).name, 'pify');
 });