Chore: Migrate EventDispatcher to TypeScript, add tests (#6673)

packages/lib/EventDispatcher.test.ts

@@ -0,0 +1,137 @@
+import EventDispatcher from './EventDispatcher';
+
+enum TestKey {
+    FooEvent,
+    BarEvent,
+    BazEvent,
+}
+
+describe('EventDispatcher', () => {
+	it('should trigger after adding a listener', () => {
+		const dispatcher = new EventDispatcher<TestKey, void>();
+		let calledCount = 0;
+		dispatcher.on(TestKey.FooEvent, () => {
+			calledCount ++;
+		});
+
+		expect(calledCount).toBe(0);
+		dispatcher.dispatch(TestKey.FooEvent);
+		expect(calledCount).toBe(1);
+	});
+
+	it('should not trigger after removing a listener', () => {
+		const dispatcher = new EventDispatcher<TestKey, void>();
+		let calledCount = 0;
+		const handle = dispatcher.on(TestKey.FooEvent, () => {
+			calledCount ++;
+		});
+
+		handle.remove();
+
+		expect(calledCount).toBe(0);
+		dispatcher.dispatch(TestKey.FooEvent);
+		expect(calledCount).toBe(0);
+	});
+
+	it('adding and removing listeners should not affect other listeners', () => {
+		const dispatcher = new EventDispatcher<TestKey, void>();
+
+		let fooCount = 0;
+		const fooListener = dispatcher.on(TestKey.FooEvent, () => {
+			fooCount ++;
+		});
+
+		let barCount = 0;
+		const barListener1 = dispatcher.on(TestKey.BarEvent, () => {
+			barCount ++;
+		});
+		const barListener2 = dispatcher.on(TestKey.BarEvent, () => {
+			barCount += 3;
+		});
+		const barListener3 = dispatcher.on(TestKey.BarEvent, () => {
+			barCount += 2;
+		});
+
+		dispatcher.dispatch(TestKey.BarEvent);
+		expect(barCount).toBe(6);
+
+		dispatcher.dispatch(TestKey.FooEvent);
+		expect(barCount).toBe(6);
+		expect(fooCount).toBe(1);
+
+		fooListener.remove();
+		barListener2.remove();
+
+		// barListener2 shouldn't be fired
+		dispatcher.dispatch(TestKey.BarEvent);
+		expect(barCount).toBe(9);
+
+		// The BazEvent shouldn't change fooCount or barCount
+		dispatcher.dispatch(TestKey.BazEvent);
+		expect(barCount).toBe(9);
+		expect(fooCount).toBe(1);
+
+		// Removing a listener for the first time should return true (it removed the listener)
+		// and false all subsequent times
+		expect(barListener1.remove()).toBe(true);
+		expect(barListener1.remove()).toBe(false);
+		expect(barListener3.remove()).toBe(true);
+	});
+
+	it('should fire all un-removed listeners if removing a listener in a listener', () => {
+		const dispatcher = new EventDispatcher<TestKey, void>();
+
+		let count = 0;
+		const barListener = () => {
+		};
+		const bazListener = () => {
+			count += 5;
+		};
+		const fooListener = () => {
+			count ++;
+			dispatcher.off(TestKey.FooEvent, barListener);
+		};
+		dispatcher.on(TestKey.FooEvent, barListener);
+		dispatcher.on(TestKey.FooEvent, fooListener);
+		dispatcher.on(TestKey.FooEvent, bazListener);
+
+		// Removing a listener shouldn't cause other listeners to be skipped
+		dispatcher.dispatch(TestKey.FooEvent);
+
+		expect(count).toBe(6);
+	});
+
+	it('should send correct data associated with events', () => {
+		const dispatcher = new EventDispatcher<TestKey, string>();
+
+		let lastResult = '';
+		const resultListener = (result: string) => {
+			lastResult = result;
+		};
+
+		dispatcher.on(TestKey.BarEvent, resultListener);
+
+		dispatcher.dispatch(TestKey.BazEvent, 'Testing...');
+		expect(lastResult).toBe('');
+
+		dispatcher.dispatch(TestKey.BarEvent, 'Test.');
+		dispatcher.off(TestKey.BarEvent, resultListener);
+
+		dispatcher.dispatch(TestKey.BarEvent, 'Testing.');
+		expect(lastResult).toBe('Test.');
+	});
+
+	it('should work if imported using require(...).default', () => {
+		const Dispatcher = require('./EventDispatcher').default;
+		const dispatcher = new Dispatcher();
+
+		let pass = false;
+		dispatcher.on('Evnt', () => {
+			pass = true;
+		});
+
+		expect(pass).toBe(false);
+		dispatcher.dispatch('Evnt');
+		expect(pass).toBe(true);
+	});
+});