From 6a4b60bef8f62e69d22772a35e3d4dfd33f15a04 Mon Sep 17 00:00:00 2001
From: Dave Brudner <32269552+dbrudner@users.noreply.github.com>
Date: Fri, 20 Mar 2020 10:55:48 -0500
Subject: [PATCH] Component emitter event (#43125)

* component-emitter: adding Event generic

* component-emitter: adding tests for Event generic
---
 .../component-emitter-tests.ts                | 27 +++++++++++++++++++
 types/component-emitter/index.d.ts            | 14 +++++-----
 2 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/types/component-emitter/component-emitter-tests.ts b/types/component-emitter/component-emitter-tests.ts
index 3d2ed7252a..fc4faefef1 100644
--- a/types/component-emitter/component-emitter-tests.ts
+++ b/types/component-emitter/component-emitter-tests.ts
@@ -50,3 +50,30 @@ emitter.listeners('some-recurring-event')
 emitter.hasListeners('some-recurring-event')
 
 emitter.emit('some-event').emit("I can use chaining!")
+
+let recurlyEmitter: Emitter<'change' | 'field:submit'> = new Emitter();
+
+recurlyEmitter.on('change', handleSomeRecurringEvent);
+// $ExpectError
+recurlyEmitter.on('some-recurring-event', handleSomeRecurringEvent);
+
+recurlyEmitter.once('field:submit', (event_data: any) => {console.log('handle some-single-shot-event')})
+// $ExpectError
+recurlyEmitter.once('some-single-shot-event', (event_data: any) => {console.log('handle some-single-shot-event')})
+
+recurlyEmitter.off()
+recurlyEmitter.off('change')
+// $ExpectError
+recurlyEmitter.off('some-recurring-event')
+
+recurlyEmitter.emit('field:submit', event_data)
+// $ExpectError
+recurlyEmitter.emit('some-recurring-event', event_data)
+
+recurlyEmitter.listeners('change')
+// $ExpectError
+recurlyEmitter.listeners('some-recurring-event')
+
+recurlyEmitter.hasListeners("field:submit");
+// $ExpectError
+recurlyEmitter.hasListeners('some-recurring-event')
diff --git a/types/component-emitter/index.d.ts b/types/component-emitter/index.d.ts
index 16332270e1..0b089914f2 100644
--- a/types/component-emitter/index.d.ts
+++ b/types/component-emitter/index.d.ts
@@ -5,13 +5,13 @@
 
 // TypeScript Version: 2.2
 
-interface Emitter {
-    on(event: string, listener: Function): Emitter;
-    once(event: string, listener: Function): Emitter;
-    off(event?: string, listener?: Function): Emitter;
-    emit(event: string, ...args: any[]): Emitter;
-    listeners(event: string): Function[];
-    hasListeners(event: string): boolean;
+interface Emitter<Event = string> {
+    on(event: Event, listener: Function): Emitter;
+    once(event: Event, listener: Function): Emitter;
+    off(event?: Event, listener?: Function): Emitter;
+    emit(event: Event, ...args: any[]): Emitter;
+    listeners(event: Event): Function[];
+    hasListeners(event: Event): boolean;
 }
 
 declare const Emitter: {