Merge pull request #37 from Financial-Times/matth/fix-semaphore

Fix semaphore

src/run-parallel.js

@@ -1,9 +1,9 @@
-const Semaphore = require('async-sema');
+const { Sema } = require('async-sema');
 const logger = require('./logger');
 const EventedQueue = require('./evented-queue');
 
 module.exports = (tasks = [], concurrency = 1, preserveOrder = false) => {
-	const semaphore = new Semaphore(concurrency);
+	const semaphore = new Sema(concurrency);
 	const queue = new EventedQueue();
 
 	logger.info(`Executing up to ${concurrency} tasks at a time`);

test/src/run-parallel.spec.js

@@ -0,0 +1,94 @@
+const subject = require('../../src/run-parallel');
+
+const wait = (ms = 10) => new Promise((resolve) => setTimeout(resolve, ms));
+
+const noop = () => {};
+
+function createTask(name, onStart, onEnd, time = 10, allDependencies = []) {
+	return {
+		apply: () => {
+			onStart();
+			return wait(time).then(onEnd);
+		},
+		pkg: {
+			name,
+			allDependencies
+		}
+	};
+}
+
+describe('src/run-parallel', () => {
+	it('executes each task', async () => {
+		const complete = [];
+
+		const tasks = [
+			createTask('a', noop, () => complete.push('a')),
+			createTask('b', noop, () => complete.push('b')),
+			createTask('c', noop, () => complete.push('c'))
+		];
+
+		await subject(tasks);
+
+		expect(complete.length).toEqual(3);
+	});
+
+	describe('with preserve order option', () => {
+		it('waits for dependent tasks to finish', async () => {
+			const complete = []
+
+			const tasks = [
+				createTask(
+					'a',
+					() => expect(complete.length).toEqual(0),
+					() => complete.push('a'),
+					100
+				),
+				createTask(
+					'b',
+					() => expect(complete.length).toEqual(0),
+					() => complete.push('b'),
+					10
+				),
+				createTask(
+					'c',
+					() => expect(complete).toEqual(expect.arrayContaining(['a', 'b'])),
+					() => complete.push('c'),
+					10,
+					['a', 'b']
+				)
+			];
+
+			await subject(tasks, 10, true);
+		});
+	});
+
+	describe('without preserve order option', () => {
+		it('waits for dependent tasks to finish', async () => {
+			const complete = []
+
+			const tasks = [
+				createTask(
+					'a',
+					() => expect(complete.length).toEqual(0),
+					() => complete.push('a'),
+					100
+				),
+				createTask(
+					'b',
+					() => expect(complete.length).toEqual(0),
+					() => complete.push('b'),
+					10
+				),
+				createTask(
+					'c',
+					() => expect(complete.length).toEqual(0),
+					() => complete.push('c'),
+					10,
+					['a', 'b']
+				)
+			];
+
+			await subject(tasks, 10, false);
+		});
+	});
+});