Fix missing methods in Keyboard module

Summary:
They keyboard module is an instance of `NativeEventEmitter` which is an instance of `EventEmitter`. But the exported module only has a small subset of the APIs. This broke existing codebases which are using the methods not exported currently.

The PR just reassigns the variable before exporting so that the actual module is exported instead of the dummy object used for documentation. It also fixes a layout issue in the documentation.
Closes https://github.com/facebook/react-native/pull/10671

Differential Revision: D4110355

fbshipit-source-id: a6757f3ca8c2494970ba221b10a7e6e9a5f2d64d

Libraries/Components/Keyboard/Keyboard.js

@@ -11,20 +11,41 @@
  */
 'use strict';
 
+const invariant = require('fbjs/lib/invariant');
 const NativeEventEmitter = require('NativeEventEmitter');
 const KeyboardObserver = require('NativeModules').KeyboardObserver;
 const dismissKeyboard = require('dismissKeyboard');
 const KeyboardEventEmitter = new NativeEventEmitter(KeyboardObserver);
 
+type KeyboardEventName =
+  | 'keyboardWillShow'
+  | 'keyboardDidShow'
+  | 'keyboardWillHide'
+  | 'keyboardDidHide'
+  | 'keyboardWillChangeFrame'
+  | 'keyboardDidChangeFrame';
+
+type KeyboardEventData = {
+  endCoordinates: {
+    width: number,
+    height: number,
+    screenX: number,
+    screenY: number,
+  },
+};
+
+type KeyboardEventListener = (e: KeyboardEventData) => void;
+
 // The following object exists for documentation purposes
 // Actual work happens in
 // https://github.com/facebook/react-native/blob/master/Libraries/EventEmitter/NativeEventEmitter.js
+
 /**
- * `Keyboard` component to control keyboard events.
+ * `Keyboard` module to control keyboard events.
  *
  * ### Usage
  *
- * The Keyboard component allows you to listen for native events and react to them, as
+ * The Keyboard module allows you to listen for native events and react to them, as
  * well as make changes to the keyboard, like dismissing it.
  *
  *```
@@ -60,16 +81,17 @@ const KeyboardEventEmitter = new NativeEventEmitter(KeyboardObserver);
  * }
  *```
  */
-module.exports = {
 
+let Keyboard = {
   /**
    * The `addListener` function connects a JavaScript function to an identified native
    * keyboard notification event.
    *
    * This function then returns the reference to the listener.
    *
-   * @param {string} nativeEvent The `nativeEvent` is the string that identifies the event you're listening for.  This
+   * @param {string} eventName The `nativeEvent` is the string that identifies the event you're listening for.  This
    *can be any of the following:
+   *
    * - `keyboardWillShow`
    * - `keyboardDidShow`
    * - `keyboardWillHide`
@@ -77,10 +99,20 @@ module.exports = {
    * - `keyboardWillChangeFrame`
    * - `keyboardDidChangeFrame`
    *
-   * @param {function} jsFunction function to be called when the event fires.
+   * @param {function} callback function to be called when the event fires.
    */
-  addListener (nativeEvent: string, jsFunction: Function) {
+  addListener(eventName: KeyboardEventName, callback: KeyboardEventListener) {
-    return KeyboardEventEmitter.addListener(nativeEvent, jsFunction);
+    invariant(false, 'Dummy method used for documentation');
+  },
+
+  /**
+   * Removes a specific listener.
+   *
+   * @param {string} eventName The `nativeEvent` is the string that identifies the event you're listening for.
+   * @param {function} callback function to be called when the event fires.
+   */
+  removeListener(eventName: KeyboardEventName, callback: Function) {
+    invariant(false, 'Dummy method used for documentation');
   },
 
   /**
@@ -88,24 +120,21 @@ module.exports = {
    *
    * @param {string} eventType The native event string listeners are watching which will be removed.
    */
-  removeAllListeners (eventType: string) {
+  removeAllListeners(eventName: KeyboardEventName) {
-    KeyboardEventEmitter.removeAllListeners(eventType);
+    invariant(false, 'Dummy method used for documentation');
-  },
-
-  /**
-   * Removes a specific subscription.
-   *
-   * @param {EmitterSubscription} subscription The subscription emitter to be removed.
-   */
-  removeSubscription (subscription: Object) {
-    KeyboardEventEmitter.removeSubscription(subscription);
   },
 
   /**
    * Dismisses the active keyboard and removes focus.
    */
   dismiss() {
-    dismissKeyboard();
+    invariant(false, 'Dummy method used for documentation');
   }
-
 };
+
+// Throw away the dummy object and reassign it to original module
+Keyboard = KeyboardEventEmitter;
+Keyboard.dismiss = dismissKeyboard;
+
+module.exports = Keyboard;
+