Align EventEmitter definitions with TypeScript (#49206)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/49206

Changelog: [Internal]

Reviewed By: huntie

Differential Revision: D68953500

fbshipit-source-id: 0e936e8423f8792db34d6b44b1620dde5bd13a47

packages/react-native/Libraries/EventEmitter/NativeEventEmitter.js

@@ -26,6 +26,9 @@ interface NativeModule {
 
 export type {EventSubscription};
 
+// $FlowFixMe[unclear-type] unclear type of events
+type UnsafeObject = Object;
+
 /**
  * `NativeEventEmitter` is intended for use by Native Modules to emit events to
  * JavaScript listeners. If a `NativeModule` is supplied to the constructor, it
@@ -36,8 +39,11 @@ export type {EventSubscription};
  * This means event names must be globally unique, and it means that call sites
  * can theoretically listen to `RCTDeviceEventEmitter` (although discouraged).
  */
-export default class NativeEventEmitter<TEventToArgsMap: {...}>
-  implements IEventEmitter<TEventToArgsMap>
+export default class NativeEventEmitter<
+  TEventToArgsMap: $ReadOnly<
+    Record<string, $ReadOnlyArray<UnsafeObject>>,
+  > = $ReadOnly<Record<string, $ReadOnlyArray<UnsafeObject>>>,
+> implements IEventEmitter<TEventToArgsMap>
 {
   _nativeModule: ?NativeModule;
 

packages/react-native/Libraries/EventEmitter/__mocks__/NativeEventEmitter.js

@@ -18,8 +18,9 @@ import RCTDeviceEventEmitter from '../RCTDeviceEventEmitter';
 /**
  * Mock `NativeEventEmitter` to ignore Native Modules.
  */
-export default class NativeEventEmitter<TEventToArgsMap: {...}>
-  implements IEventEmitter<TEventToArgsMap>
+export default class NativeEventEmitter<
+  TEventToArgsMap: $ReadOnly<Record<string, $ReadOnlyArray<mixed>>>,
+> implements IEventEmitter<TEventToArgsMap>
 {
   addListener<TEvent: $Keys<TEventToArgsMap>>(
     eventType: TEvent,

packages/react-native/Libraries/__tests__/__snapshots__/public-api-test.js.snap

@@ -4198,8 +4198,12 @@ exports[`public API should not change unintentionally Libraries/EventEmitter/Nat
   removeListeners(count: number): void;
 }
 export type { EventSubscription };
-declare export default class NativeEventEmitter<TEventToArgsMap: { ... }>
-  implements IEventEmitter<TEventToArgsMap>
+type UnsafeObject = Object;
+declare export default class NativeEventEmitter<
+  TEventToArgsMap: $ReadOnly<
+    Record<string, $ReadOnlyArray<UnsafeObject>>,
+  > = $ReadOnly<Record<string, $ReadOnlyArray<UnsafeObject>>>,
+> implements IEventEmitter<TEventToArgsMap>
 {
   constructor(nativeModule: ?NativeModule): void;
   addListener<TEvent: $Keys<TEventToArgsMap>>(
@@ -8801,10 +8805,13 @@ exports[`public API should not change unintentionally Libraries/vendor/core/Erro
 `;
 
 exports[`public API should not change unintentionally Libraries/vendor/emitter/EventEmitter.js 1`] = `
-"export interface EventSubscription {
+"type UnsafeObject = Object;
+export interface EventSubscription {
   remove(): void;
 }
-export interface IEventEmitter<TEventToArgsMap: { ... }> {
+export interface IEventEmitter<
+  TEventToArgsMap: $ReadOnly<Record<string, $ReadOnlyArray<UnsafeObject>>>,
+> {
   addListener<TEvent: $Keys<TEventToArgsMap>>(
     eventType: TEvent,
     listener: (...args: TEventToArgsMap[TEvent]) => mixed,
@@ -8817,8 +8824,11 @@ export interface IEventEmitter<TEventToArgsMap: { ... }> {
   removeAllListeners<TEvent: $Keys<TEventToArgsMap>>(eventType?: ?TEvent): void;
   listenerCount<TEvent: $Keys<TEventToArgsMap>>(eventType: TEvent): number;
 }
-declare export default class EventEmitter<TEventToArgsMap: { ... }>
-  implements IEventEmitter<TEventToArgsMap>
+declare export default class EventEmitter<
+  TEventToArgsMap: $ReadOnly<
+    Record<string, $ReadOnlyArray<UnsafeObject>>,
+  > = $ReadOnly<Record<string, $ReadOnlyArray<UnsafeObject>>>,
+> implements IEventEmitter<TEventToArgsMap>
 {
   addListener<TEvent: $Keys<TEventToArgsMap>>(
     eventType: TEvent,

packages/react-native/Libraries/vendor/emitter/EventEmitter.js

@@ -8,11 +8,16 @@
  * @format
  */
 
+// $FlowFixMe[unclear-type] unclear type of events
+type UnsafeObject = Object;
+
 export interface EventSubscription {
   remove(): void;
 }
 
-export interface IEventEmitter<TEventToArgsMap: {...}> {
+export interface IEventEmitter<
+  TEventToArgsMap: $ReadOnly<Record<string, $ReadOnlyArray<UnsafeObject>>>,
+> {
   addListener<TEvent: $Keys<TEventToArgsMap>>(
     eventType: TEvent,
     listener: (...args: TEventToArgsMap[TEvent]) => mixed,
@@ -35,7 +40,9 @@ interface Registration<TArgs> {
   +remove: () => void;
 }
 
-type Registry<TEventToArgsMap: {...}> = {
+type Registry<
+  TEventToArgsMap: $ReadOnly<Record<string, $ReadOnlyArray<UnsafeObject>>>,
+> = {
   [K in keyof TEventToArgsMap]: Set<Registration<TEventToArgsMap[K]>>,
 };
 
@@ -59,8 +66,11 @@ type Registry<TEventToArgsMap: {...}> = {
  *   emitter.emit('error', new Error('Resource not found'));
  *
  */
-export default class EventEmitter<TEventToArgsMap: {...}>
-  implements IEventEmitter<TEventToArgsMap>
+export default class EventEmitter<
+  TEventToArgsMap: $ReadOnly<
+    Record<string, $ReadOnlyArray<UnsafeObject>>,
+  > = $ReadOnly<Record<string, $ReadOnlyArray<UnsafeObject>>>,
+> implements IEventEmitter<TEventToArgsMap>
 {
   // $FlowFixMe[incompatible-type]
   #registry: Registry<TEventToArgsMap> = {};
@@ -81,7 +91,7 @@ export default class EventEmitter<TEventToArgsMap: {...}>
     }
     const registrations = allocate<
       TEventToArgsMap,
-      TEvent,
+      $Keys<TEventToArgsMap>,
       TEventToArgsMap[TEvent],
     >(this.#registry, eventType);
     const registration: Registration<TEventToArgsMap[TEvent]> = {
@@ -136,20 +146,22 @@ export default class EventEmitter<TEventToArgsMap: {...}>
    * Returns the number of registered listeners for the supplied event.
    */
   listenerCount<TEvent: $Keys<TEventToArgsMap>>(eventType: TEvent): number {
-    const registrations: ?Set<Registration<mixed>> = this.#registry[eventType];
+    const registrations: ?Set<Registration<TEventToArgsMap[TEvent]>> =
+      this.#registry[eventType];
     return registrations == null ? 0 : registrations.size;
   }
 }
 
 function allocate<
-  TEventToArgsMap: {...},
+  TEventToArgsMap: $ReadOnly<Record<string, $ReadOnlyArray<UnsafeObject>>>,
   TEvent: $Keys<TEventToArgsMap>,
   TEventArgs: TEventToArgsMap[TEvent],
 >(
   registry: Registry<TEventToArgsMap>,
   eventType: TEvent,
-): Set<Registration<TEventArgs>> {
-  let registrations: ?Set<Registration<TEventArgs>> = registry[eventType];
+): Set<Registration<TEventToArgsMap[TEvent]>> {
+  let registrations: ?Set<Registration<TEventToArgsMap[TEvent]>> =
+    registry[eventType];
   if (registrations == null) {
     registrations = new Set();
     registry[eventType] = registrations;

scripts/build/build-types/buildTypes.js

@@ -33,6 +33,7 @@ const ENTRY_POINTS = [
   'packages/react-native/Libraries/Settings/Settings.js',
   'packages/react-native/Libraries/Performance/Systrace.js',
   'packages/react-native/Libraries/LogBox/LogBox.js',
+  'packages/react-native/Libraries/vendor/emitter/EventEmitter.js',
 ];
 
 /**