Add stopOnError option (#16)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

index.d.ts

@@ -6,6 +6,13 @@ declare namespace pMap {
 		@default Infinity
 		*/
 		concurrency?: number;
+
+		/**
+		When set to `false`, instead of stopping when a promise rejects, it will wait for all the promises to settle and then reject with an [aggregated error](https://github.com/sindresorhus/aggregate-error) containing all the errors from the rejected promises.
+
+		@default true
+		*/
+		stopOnError?: boolean;
 	}
 
 	/**

index.js

@@ -1,21 +1,24 @@
 'use strict';
+const AggregateError = require('aggregate-error');
 
 const pMap = (iterable, mapper, options) => new Promise((resolve, reject) => {
 	options = Object.assign({
-		concurrency: Infinity
+		concurrency: Infinity,
+		stopOnError: true
 	}, options);
 
 	if (typeof mapper !== 'function') {
 		throw new TypeError('Mapper function is required');
 	}
 
-	const {concurrency} = options;
+	const {concurrency, stopOnError} = options;
 
 	if (!(typeof concurrency === 'number' && concurrency >= 1)) {
 		throw new TypeError(`Expected \`concurrency\` to be a number from 1 and up, got \`${concurrency}\` (${typeof concurrency})`);
 	}
 
 	const ret = [];
+	const errors = [];
 	const iterator = iterable[Symbol.iterator]();
 	let isRejected = false;
 	let isIterableDone = false;
@@ -35,7 +38,11 @@ const pMap = (iterable, mapper, options) => new Promise((resolve, reject) => {
 			isIterableDone = true;
 
 			if (resolvingCount === 0) {
-				resolve(ret);
+				if (!stopOnError && errors.length !== 0) {
+					reject(new AggregateError(errors));
+				} else {
+					resolve(ret);
+				}
 			}
 
 			return;
@@ -52,8 +59,14 @@ const pMap = (iterable, mapper, options) => new Promise((resolve, reject) => {
 					next();
 				},
 				error => {
-					isRejected = true;
-					reject(error);
+					if (stopOnError) {
+						isRejected = true;
+						reject(error);
+					} else {
+						errors.push(error);
+						resolvingCount--;
+						next();
+					}
 				}
 			);
 	};

index.test-d.ts

@@ -21,6 +21,7 @@ expectType<Mapper<string, string | number>>(multiResultTypeMapper);
 
 expectType<Options>({});
 expectType<Options>({concurrency: 0});
+expectType<Options>({stopOnError: false});
 
 expectType<Promise<string[]>>(pMap(sites, asyncMapper));
 expectType<Promise<string[]>>(pMap(sites, asyncMapper, {concurrency: 2}));

package.json

@@ -37,6 +37,9 @@
 		"parallel",
 		"bluebird"
 	],
+	"dependencies": {
+		"aggregate-error": "^2.0.0"
+	},
 	"devDependencies": {
 		"ava": "^1.4.1",
 		"delay": "^4.1.0",

readme.md

@@ -68,6 +68,13 @@ Minimum: `1`
 
 Number of concurrently pending promises returned by `mapper`.
 
+##### stopOnError
+
+Type: `boolean`<br>
+Default: `true`
+
+When set to `false`, instead of stopping when a promise rejects, it will wait for all the promises to settle and then reject with an [aggregated error](https://github.com/sindresorhus/aggregate-error) containing all the errors from the rejected promises.
+
 
 ## Related
 

test.js

@@ -3,6 +3,7 @@ import delay from 'delay';
 import inRange from 'in-range';
 import timeSpan from 'time-span';
 import randomInt from 'random-int';
+import AggregateError from 'aggregate-error';
 import pMap from '.';
 
 const input = [
@@ -11,6 +12,20 @@ const input = [
 	[30, 100]
 ];
 
+const errorInput1 = [
+	[20, 200],
+	[30, 100],
+	Promise.reject(new Error('foo')),
+	Promise.reject(new Error('bar'))
+];
+
+const errorInput2 = [
+	[20, 200],
+	Promise.reject(new Error('bar')),
+	[30, 100],
+	Promise.reject(new Error('foo'))
+];
+
 const mapper = ([value, ms]) => delay(ms, {value});
 
 test('main', async t => {
@@ -69,3 +84,14 @@ test('enforce number in options.concurrency', async t => {
 	await t.notThrowsAsync(pMap([], () => {}, {concurrency: 10}));
 	await t.notThrowsAsync(pMap([], () => {}, {concurrency: Infinity}));
 });
+
+test('immediately rejects when stopOnError is true', async t => {
+	await t.throwsAsync(pMap(errorInput1, mapper, {concurrency: 1}), 'foo');
+	await t.throwsAsync(pMap(errorInput2, mapper, {concurrency: 1}), 'bar');
+});
+
+test('aggregate errors when stopOnError is false', async t => {
+	await t.notThrowsAsync(pMap(input, mapper, {concurrency: 1, stopOnError: false}));
+	await t.throwsAsync(pMap(errorInput1, mapper, {concurrency: 1, stopOnError: false}), {instanceOf: AggregateError, message: /foo(.|\n)*bar/});
+	await t.throwsAsync(pMap(errorInput2, mapper, {concurrency: 1, stopOnError: false}), {instanceOf: AggregateError, message: /bar(.|\n)*foo/});
+});