From 80685d52b8ef1e239329c137a45b567b0b65ef76 Mon Sep 17 00:00:00 2001
From: Xin Chen <xch@meta.com>
Date: Mon, 21 Aug 2023 13:25:31 -0700
Subject: [PATCH] Add systrace for event type when calling
 RCTDeviceEventEmitter (#39085)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/39085

Adding arguments in systrace for event emitter event types. This is helpful to understand why sometimes JS render is triggered from native side.

Changelog:
[Internal] - Add event type information from native to js event emitter calls

Reviewed By: rshest

Differential Revision: D48448904

fbshipit-source-id: cbb4b86e781384d56205fec23931cd773e4a58a8
---
 .../EventEmitter/RCTDeviceEventEmitter.js     | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/packages/react-native/Libraries/EventEmitter/RCTDeviceEventEmitter.js b/packages/react-native/Libraries/EventEmitter/RCTDeviceEventEmitter.js
index 25698329188..d53df915597 100644
--- a/packages/react-native/Libraries/EventEmitter/RCTDeviceEventEmitter.js
+++ b/packages/react-native/Libraries/EventEmitter/RCTDeviceEventEmitter.js
@@ -10,6 +10,7 @@
 
 import type {IEventEmitter} from '../vendor/emitter/EventEmitter';
 
+import {beginEvent, endEvent} from '../Performance/Systrace';
 import EventEmitter from '../vendor/emitter/EventEmitter';
 
 // FIXME: use typed events
@@ -21,12 +22,22 @@ type RCTDeviceEventDefinitions = $FlowFixMe;
  *
  * NativeModules that emit events should instead subclass `NativeEventEmitter`.
  */
-const RCTDeviceEventEmitter: IEventEmitter<RCTDeviceEventDefinitions> =
-  new EventEmitter();
+class RCTDeviceEventEmitter extends EventEmitter<RCTDeviceEventDefinitions> {
+  // Add systrace to RCTDeviceEventEmitter.emit method for debugging
+  emit<TEvent: $Keys<RCTDeviceEventDefinitions>>(
+    eventType: TEvent,
+    ...args: RCTDeviceEventDefinitions[TEvent]
+  ): void {
+    beginEvent(() => `RCTDeviceEventEmitter.emit#${eventType}`);
+    super.emit(eventType, ...args);
+    endEvent();
+  }
+}
+const instance = new RCTDeviceEventEmitter();
 
 Object.defineProperty(global, '__rctDeviceEventEmitter', {
   configurable: true,
-  value: RCTDeviceEventEmitter,
+  value: instance,
 });
 
-export default (RCTDeviceEventEmitter: IEventEmitter<RCTDeviceEventDefinitions>);
+export default (instance: IEventEmitter<RCTDeviceEventDefinitions>);