event buffer, nextTick, tests

src/vs/base/common/event.ts

@@ -375,7 +375,7 @@ export function stopwatch<T>(event: Event<T>): Event<number> {
  * // 4
  * ```
  */
-export function buffer<T>(event: Event<T>): Event<T> {
+export function buffer<T>(event: Event<T>, nextTick = false): Event<T> {
 	let buffer: T[] = [];
 	let listener = event(e => {
 		if (buffer) {
@@ -385,6 +385,11 @@ export function buffer<T>(event: Event<T>): Event<T> {
 		}
 	});
 
+	const flush = () => {
+		buffer.forEach(e => emitter.fire(e));
+		buffer = null;
+	};
+
 	const emitter = new Emitter<T>({
 		onFirstListenerAdd() {
 			if (!listener) {
@@ -394,8 +399,11 @@ export function buffer<T>(event: Event<T>): Event<T> {
 
 		onFirstListenerDidAdd() {
 			if (buffer) {
-				buffer.forEach(e => emitter.fire(e));
-				buffer = null;
+				if (nextTick) {
+					setTimeout(flush);
+				} else {
+					flush();
+				}
 			}
 		},
 

src/vs/base/test/common/event.test.ts

@@ -5,7 +5,7 @@
 'use strict';
 
 import * as assert from 'assert';
-import Event, {Emitter, fromEventEmitter, debounceEvent, EventBufferer, once, fromPromise, stopwatch} from 'vs/base/common/event';
+import Event, {Emitter, fromEventEmitter, debounceEvent, EventBufferer, once, fromPromise, stopwatch, buffer} from 'vs/base/common/event';
 import {IDisposable} from 'vs/base/common/lifecycle';
 import {EventEmitter} from 'vs/base/common/eventEmitter';
 import Errors = require('vs/base/common/errors');
@@ -211,7 +211,9 @@ suite('Event',function(){
 	});
 });
 
-suite('EventBufferer', () => {
+suite('Event utils', () => {
+
+	suite('EventBufferer', () => {
 
 		test('should not buffer when not wrapped', () => {
 			const bufferer = new EventBufferer();
@@ -283,9 +285,9 @@ suite('EventBufferer', () => {
 			listener1.dispose();
 			listener2.dispose();
 		});
-});
+	});
 
-suite('fromPromise', () => {
+	suite('fromPromise', () => {
 
 		test('should emit when done', () => {
 			let count = 0;
@@ -329,9 +331,9 @@ suite('fromPromise', () => {
 				});
 			});
 		});
-});
+	});
 
-suite('stopwatch', () => {
+	suite('stopwatch', () => {
 
 		test('should emit', () => {
 			const emitter = new Emitter<void>();
@@ -351,4 +353,55 @@ suite('stopwatch', () => {
 				setTimeout(() => emitter.fire(), 10);
 			});
 		});
+	});
+
+	suite('buffer', () => {
+
+		test('should buffer events', () => {
+			const result = [];
+			const emitter = new Emitter<number>();
+			const event = emitter.event;
+			const bufferedEvent = buffer(event);
+
+			emitter.fire(1);
+			emitter.fire(2);
+			emitter.fire(3);
+			assert.deepEqual(result, []);
+
+			const listener = bufferedEvent(num => result.push(num));
+			assert.deepEqual(result, [1,2,3]);
+
+			emitter.fire(4);
+			assert.deepEqual(result, [1,2,3,4]);
+
+			listener.dispose();
+			emitter.fire(5);
+			assert.deepEqual(result, [1,2,3,4]);
+		});
+
+		test('should buffer events on next tick', () => {
+			const result = [];
+			const emitter = new Emitter<number>();
+			const event = emitter.event;
+			const bufferedEvent = buffer(event, true);
+
+			emitter.fire(1);
+			emitter.fire(2);
+			emitter.fire(3);
+			assert.deepEqual(result, []);
+
+			const listener = bufferedEvent(num => result.push(num));
+			assert.deepEqual(result, []);
+
+			return TPromise.timeout(10).then(() => {
+				emitter.fire(4);
+				assert.deepEqual(result, [1,2,3,4]);
+
+				listener.dispose();
+				emitter.fire(5);
+				assert.deepEqual(result, [1,2,3,4]);
+			});
+		});
+	});
+
 });
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