RN: Restore Deprecated Event Methods

Summary:
Restore deprecated event listener removal methods in order to minimize breaking changes for the next release. The methods will work, but they will not report a warning via `console.error`.

Changelog:
[General][Added] - `EventEmitter.removeListener` now emits a deprecation notice.
[General][Added] - Restored `AppState.removeEventListener` with a deprecation notice.
[General][Added] - Restored `Keyboard.removeEventListener` with a deprecation notice.
[General][Added] - Restored `Linking.removeEventListener` with a deprecation notice.

Reviewed By: nadiia, kacieb

Differential Revision: D26589441

fbshipit-source-id: 7d89982a182cf2163136e157d4c1beee91c30393

Author: yungsters

Libraries/AppState/AppState.js

@@ -123,6 +123,39 @@ class AppState {
     }
     throw new Error('Trying to subscribe to unknown event: ' + type);
   }
+
+  /**
+   * @deprecated Use `remove` on the EventSubscription from `addEventListener`.
+   */
+  removeEventListener<K: $Keys<AppStateEventDefinitions>>(
+    type: K,
+    listener: (...$ElementType<AppStateEventDefinitions, K>) => mixed,
+  ): void {
+    const emitter = this._emitter;
+    if (emitter == null) {
+      throw new Error('Cannot use AppState when `isAvailable` is false.');
+    }
+    // NOTE: This will report a deprecation notice via `console.error`.
+    switch (type) {
+      case 'change':
+        // $FlowIssue[invalid-tuple-arity] Flow cannot refine handler based on the event type
+        // $FlowIssue[incompatible-call]
+        emitter.removeListener('appStateDidChange', listener);
+        return;
+      case 'memoryWarning':
+        // $FlowIssue[invalid-tuple-arity] Flow cannot refine handler based on the event type
+        // $FlowIssue[incompatible-call]
+        emitter.removeListener('memoryWarning', listener);
+        return;
+      case 'blur':
+      case 'focus':
+        // $FlowIssue[invalid-tuple-arity] Flow cannot refine handler based on the event type
+        // $FlowIssue[incompatible-call]
+        emitter.addListener('appStateFocusChange', listener);
+        return;
+    }
+    throw new Error('Trying to unsubscribe from unknown event: ' + type);
+  }
 }
 
 module.exports = (new AppState(): AppState);

Libraries/Components/Keyboard/Keyboard.js

@@ -137,6 +137,17 @@ class Keyboard {
     return this._emitter.addListener(eventType, listener);
   }
 
+  /**
+   * @deprecated Use `remove` on the EventSubscription from `addEventListener`.
+   */
+  removeEventListener<K: $Keys<KeyboardEventDefinitions>>(
+    eventType: K,
+    listener: (...$ElementType<KeyboardEventDefinitions, K>) => mixed,
+  ): void {
+    // NOTE: This will report a deprecation notice via `console.error`.
+    this._emitter.removeListener(eventType, listener);
+  }
+
   /**
    * Removes all listeners for a specific event type.
    *

Libraries/EventEmitter/NativeEventEmitter.js

@@ -74,6 +74,19 @@ export default class NativeEventEmitter<TEventToArgsMap: {...}>
     };
   }
 
+  /**
+   * @deprecated Use `remove` on the EventSubscription from `addListener`.
+   */
+  removeListener<TEvent: $Keys<TEventToArgsMap>>(
+    eventType: TEvent,
+    listener: (...args: $ElementType<TEventToArgsMap, TEvent>) => mixed,
+  ): void {
+    this._nativeModule?.removeListeners(1);
+    // NOTE: This will report a deprecation notice via `console.error`.
+    // $FlowFixMe[prop-missing] - `removeListener` exists but is deprecated.
+    RCTDeviceEventEmitter.removeListener(eventType, listener);
+  }
+
   emit<TEvent: $Keys<TEventToArgsMap>>(
     eventType: TEvent,
     ...args: $ElementType<TEventToArgsMap, TEvent>

Libraries/Linking/Linking.js

@@ -46,6 +46,17 @@ class Linking extends NativeEventEmitter<LinkingEventDefinitions> {
     return this.addListener(eventType, listener);
   }
 
+  /**
+   * @deprecated Use `remove` on the EventSubscription from `addEventListener`.
+   */
+  removeEventListener<K: $Keys<LinkingEventDefinitions>>(
+    eventType: K,
+    listener: (...$ElementType<LinkingEventDefinitions, K>) => mixed,
+  ): void {
+    // NOTE: This will report a deprecation notice via `console.error`.
+    this.removeListener(eventType, listener);
+  }
+
   /**
    * Try to open the given `url` with any of the installed apps.
    *

Libraries/vendor/emitter/_EventEmitter.js

@@ -97,8 +97,7 @@ class EventEmitter<EventDefinitions: {...}>
   }
 
   /**
-   * Removes a specific subscription. Called by the `remove()` method of the
-   * subscription itself to ensure any necessary cleanup is performed.
+   * @deprecated Use `remove` on the EventSubscription from `addListener`.
    */
   removeSubscription<K: $Keys<EventDefinitions>>(
     subscription: EmitterSubscription<EventDefinitions, K>,
@@ -160,23 +159,18 @@ class EventEmitter<EventDefinitions: {...}>
   }
 
   /**
-   * Removes the given listener for event of specific type.
-   *
-   * @param {string} eventType - Name of the event to emit
-   * @param {function} listener - Function to invoke when the specified event is
-   *   emitted
-   *
-   * @example
-   *   emitter.removeListener('someEvent', function(message) {
-   *     console.log(message);
-   *   }); // removes the listener if already registered
-   *
+   * @deprecated Use `remove` on the EventSubscription from `addListener`.
    */
   removeListener<K: $Keys<EventDefinitions>>(
     eventType: K,
     // FIXME: listeners should return void instead of mixed to prevent issues
     listener: (...$ElementType<EventDefinitions, K>) => mixed,
   ): void {
+    console.error(
+      `EventEmitter.removeListener('${eventType}', ...): Method has been ` +
+        'deprecated. Please instead use `remove()` on the subscription ' +
+        'returned by `EventEmitter.addListener`.',
+    );
     const subscriptions = this._subscriber.getSubscriptionsForType(eventType);
     if (subscriptions) {
       for (let i = 0, l = subscriptions.length; i < l; i++) {