[add] NativeEventEmitter export

Export NativeEventEmitter and provide React Native's implementation.

package.json

@@ -63,7 +63,9 @@
   ],
   "lint-staged": {
     "packages/react-native-web/src/index.js": [
-      "node ./scripts/babel/createModuleMap.js"
+      "node ./scripts/babel/createModuleMap.js",
+      "prettier --write ./packages/babel-plugin-react-native-web/src/moduleMap.js",
+      "git add ./packages/babel-plugin-react-native-web/src/moduleMap.js"
     ],
     "**/*.js": [
       "prettier --write",

packages/babel-plugin-react-native-web/src/moduleMap.js

@@ -27,6 +27,7 @@ module.exports = {
   Linking: true,
   ListView: true,
   Modal: true,
+  NativeEventEmitter: true,
   NativeModules: true,
   NetInfo: true,
   PanResponder: true,

packages/react-native-web/src/exports/NativeEventEmitter/index.js

@@ -0,0 +1,11 @@
+/**
+ * Copyright (c) 2016-present, Nicolas Gallagher.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+import NativeEventEmitter from '../../vendor/react-native/NativeEventEmitter';
+export default NativeEventEmitter;

packages/react-native-web/src/index.js

@@ -23,6 +23,7 @@ import Keyboard from './exports/Keyboard';
 import InteractionManager from './exports/InteractionManager';
 import LayoutAnimation from './exports/LayoutAnimation';
 import Linking from './exports/Linking';
+import NativeEventEmitter from './exports/NativeEventEmitter';
 import NetInfo from './exports/NetInfo';
 import PanResponder from './exports/PanResponder';
 import PixelRatio from './exports/PixelRatio';
@@ -93,6 +94,7 @@ export {
   Keyboard,
   LayoutAnimation,
   Linking,
+  NativeEventEmitter,
   NetInfo,
   PanResponder,
   PixelRatio,
@@ -162,6 +164,7 @@ const ReactNative = {
   Keyboard,
   LayoutAnimation,
   Linking,
+  NativeEventEmitter,
   NetInfo,
   PanResponder,
   PixelRatio,

packages/react-native-web/src/modules/NativeEventEmitter/index.js

@@ -1,22 +0,0 @@
-/**
- * Copyright (c) 2015-present, Facebook, Inc.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- *
- * @noflow
- */
-'use strict';
-
-class NativeEventEmitter {
-  addListener() {}
-  emit() {}
-  listeners() {}
-  once() {}
-  removeAllListeners() {}
-  removeCurrentListener() {}
-  removeListener() {}
-  removeSubscription() {}
-}
-
-export default NativeEventEmitter;

packages/react-native-web/src/vendor/react-native/Animated/NativeAnimatedHelper.js

@@ -11,7 +11,7 @@
 
 import invariant from 'fbjs/lib/invariant';
 import NativeModules from '../../../exports/NativeModules';
-import NativeEventEmitter from '../../../modules/NativeEventEmitter';
+import NativeEventEmitter from '../NativeEventEmitter';
 
 import type {AnimationConfig} from './animations/Animation';
 import type {EventConfig} from './AnimatedEvent';

packages/react-native-web/src/vendor/react-native/NativeEventEmitter/index.js

@@ -0,0 +1,67 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @providesModule NativeEventEmitter
+ * @flow
+ */
+'use strict';
+
+import EventEmitter from '../emitter/EventEmitter';
+import Platform from '../../../exports/Platform';
+
+import invariant from 'fbjs/lib/invariant';
+
+import type EmitterSubscription from '../emitter/EmitterSubscription';
+
+type NativeModule = {
+  +addListener: (eventType: string) => void,
+  +removeListeners: (count: number) => void,
+};
+
+/**
+ * Abstract base class for implementing event-emitting modules. This implements
+ * a subset of the standard EventEmitter node module API.
+ */
+class NativeEventEmitter extends EventEmitter {
+  _nativeModule: ?NativeModule;
+
+  constructor(nativeModule: ?NativeModule) {
+    super();
+    if (Platform.OS === 'ios') {
+      invariant(nativeModule, 'Native module cannot be null.');
+      this._nativeModule = nativeModule;
+    }
+  }
+
+  addListener(
+    eventType: string,
+    listener: Function,
+    context: ?Object,
+  ): EmitterSubscription {
+    if (this._nativeModule != null) {
+      this._nativeModule.addListener(eventType);
+    }
+    return super.addListener(eventType, listener, context);
+  }
+
+  removeAllListeners(eventType: string) {
+    invariant(eventType, 'eventType argument is required.');
+    const count = this.listeners(eventType).length;
+    if (this._nativeModule != null) {
+      this._nativeModule.removeListeners(count);
+    }
+    super.removeAllListeners(eventType);
+  }
+
+  removeSubscription(subscription: EmitterSubscription) {
+    if (this._nativeModule != null) {
+      this._nativeModule.removeListeners(1);
+    }
+    super.removeSubscription(subscription);
+  }
+}
+
+export default NativeEventEmitter;

packages/react-native-web/src/vendor/react-native/emitter/EmitterSubscription.js

@@ -0,0 +1,59 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @providesModule EmitterSubscription
+ * @flow
+ */
+'use strict';
+
+import EventSubscription from './EventSubscription';
+
+import type EventEmitter from './EventEmitter';
+import type EventSubscriptionVendor from './EventSubscriptionVendor';
+
+/**
+ * EmitterSubscription represents a subscription with listener and context data.
+ */
+class EmitterSubscription extends EventSubscription {
+
+  emitter: EventEmitter;
+  listener: Function;
+  context: ?Object;
+
+  /**
+   * @param {EventEmitter} emitter - The event emitter that registered this
+   *   subscription
+   * @param {EventSubscriptionVendor} subscriber - The subscriber that controls
+   *   this subscription
+   * @param {function} listener - Function to invoke when the specified event is
+   *   emitted
+   * @param {*} context - Optional context object to use when invoking the
+   *   listener
+   */
+  constructor(
+    emitter: EventEmitter,
+    subscriber: EventSubscriptionVendor,
+    listener: Function,
+    context: ?Object
+  ) {
+    super(subscriber);
+    this.emitter = emitter;
+    this.listener = listener;
+    this.context = context;
+  }
+
+  /**
+   * Removes this subscription from the emitter that registered it.
+   * Note: we're overriding the `remove()` method of EventSubscription here
+   * but deliberately not calling `super.remove()` as the responsibility
+   * for removing the subscription lies with the EventEmitter.
+   */
+  remove() {
+    this.emitter.removeSubscription(this);
+  }
+}
+
+export default EmitterSubscription;

packages/react-native-web/src/vendor/react-native/emitter/EventEmitter.js

@@ -0,0 +1,218 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @providesModule EventEmitter
+ * @noflow
+ * @typecheck
+ */
+'use strict';
+
+import EmitterSubscription from './EmitterSubscription';
+import EventSubscriptionVendor from './EventSubscriptionVendor';
+
+import emptyFunction from 'fbjs/lib/emptyFunction';
+import invariant from 'fbjs/lib/invariant';
+
+/**
+ * @class EventEmitter
+ * @description
+ * An EventEmitter is responsible for managing a set of listeners and publishing
+ * events to them when it is told that such events happened. In addition to the
+ * data for the given event it also sends a event control object which allows
+ * the listeners/handlers to prevent the default behavior of the given event.
+ *
+ * The emitter is designed to be generic enough to support all the different
+ * contexts in which one might want to emit events. It is a simple multicast
+ * mechanism on top of which extra functionality can be composed. For example, a
+ * more advanced emitter may use an EventHolder and EventFactory.
+ */
+class EventEmitter {
+
+  _subscriber: EventSubscriptionVendor;
+  _currentSubscription: ?EmitterSubscription;
+
+  /**
+   * @constructor
+   *
+   * @param {EventSubscriptionVendor} subscriber - Optional subscriber instance
+   *   to use. If omitted, a new subscriber will be created for the emitter.
+   */
+  constructor(subscriber: ?EventSubscriptionVendor) {
+    this._subscriber = subscriber || new EventSubscriptionVendor();
+  }
+
+  /**
+   * Adds a listener to be invoked when events of the specified type are
+   * emitted. An optional calling context may be provided. The data arguments
+   * emitted will be passed to the listener function.
+   *
+   * TODO: Annotate the listener arg's type. This is tricky because listeners
+   *       can be invoked with varargs.
+   *
+   * @param {string} eventType - Name of the event to listen to
+   * @param {function} listener - Function to invoke when the specified event is
+   *   emitted
+   * @param {*} context - Optional context object to use when invoking the
+   *   listener
+   */
+  addListener(
+    eventType: string, listener: Function, context: ?Object): EmitterSubscription {
+
+    return (this._subscriber.addSubscription(
+      eventType,
+      new EmitterSubscription(this, this._subscriber, listener, context)
+    ) : any);
+  }
+
+  /**
+   * Similar to addListener, except that the listener is removed after it is
+   * invoked once.
+   *
+   * @param {string} eventType - Name of the event to listen to
+   * @param {function} listener - Function to invoke only once when the
+   *   specified event is emitted
+   * @param {*} context - Optional context object to use when invoking the
+   *   listener
+   */
+  once(eventType: string, listener: Function, context: ?Object): EmitterSubscription {
+    return this.addListener(eventType, (...args) => {
+      this.removeCurrentListener();
+      listener.apply(context, args);
+    });
+  }
+
+  /**
+   * Removes all of the registered listeners, including those registered as
+   * listener maps.
+   *
+   * @param {?string} eventType - Optional name of the event whose registered
+   *   listeners to remove
+   */
+  removeAllListeners(eventType: ?string) {
+    this._subscriber.removeAllSubscriptions(eventType);
+  }
+
+  /**
+   * Provides an API that can be called during an eventing cycle to remove the
+   * last listener that was invoked. This allows a developer to provide an event
+   * object that can remove the listener (or listener map) during the
+   * invocation.
+   *
+   * If it is called when not inside of an emitting cycle it will throw.
+   *
+   * @throws {Error} When called not during an eventing cycle
+   *
+   * @example
+   *   var subscription = emitter.addListenerMap({
+   *     someEvent: function(data, event) {
+   *       console.log(data);
+   *       emitter.removeCurrentListener();
+   *     }
+   *   });
+   *
+   *   emitter.emit('someEvent', 'abc'); // logs 'abc'
+   *   emitter.emit('someEvent', 'def'); // does not log anything
+   */
+  removeCurrentListener() {
+    invariant(
+      !!this._currentSubscription,
+      'Not in an emitting cycle; there is no current subscription'
+    );
+    this.removeSubscription(this._currentSubscription);
+  }
+
+  /**
+   * Removes a specific subscription. Called by the `remove()` method of the
+   * subscription itself to ensure any necessary cleanup is performed.
+   */
+  removeSubscription(subscription: EmitterSubscription) {
+    invariant(
+      subscription.emitter === this,
+      'Subscription does not belong to this emitter.'
+    );
+    this._subscriber.removeSubscription(subscription);
+  }
+
+  /**
+   * Returns an array of listeners that are currently registered for the given
+   * event.
+   *
+   * @param {string} eventType - Name of the event to query
+   * @returns {array}
+   */
+  listeners(eventType: string): [EmitterSubscription] {
+    const subscriptions: ?[EmitterSubscription] = (this._subscriber.getSubscriptionsForType(eventType): any);
+    return subscriptions
+      ? subscriptions.filter(emptyFunction.thatReturnsTrue).map(
+          function(subscription) {
+            return subscription.listener;
+          })
+      : [];
+  }
+
+  /**
+   * Emits an event of the given type with the given data. All handlers of that
+   * particular type will be notified.
+   *
+   * @param {string} eventType - Name of the event to emit
+   * @param {...*} Arbitrary arguments to be passed to each registered listener
+   *
+   * @example
+   *   emitter.addListener('someEvent', function(message) {
+   *     console.log(message);
+   *   });
+   *
+   *   emitter.emit('someEvent', 'abc'); // logs 'abc'
+   */
+  emit(eventType: string) {
+    const subscriptions: ?[EmitterSubscription] = (this._subscriber.getSubscriptionsForType(eventType): any);
+    if (subscriptions) {
+      for (let i = 0, l = subscriptions.length; i < l; i++) {
+        const subscription = subscriptions[i];
+
+        // The subscription may have been removed during this event loop.
+        if (subscription) {
+          this._currentSubscription = subscription;
+          subscription.listener.apply(
+            subscription.context,
+            Array.prototype.slice.call(arguments, 1)
+          );
+        }
+      }
+      this._currentSubscription = null;
+    }
+  }
+
+  /**
+   * 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
+   *
+   */
+  removeListener(eventType: String, listener) {
+    const subscriptions: ?[EmitterSubscription] = (this._subscriber.getSubscriptionsForType(eventType): any);
+    if (subscriptions) {
+      for (let i = 0, l = subscriptions.length; i < l; i++) {
+        const subscription = subscriptions[i];
+
+        // The subscription may have been removed during this event loop.
+        // its listener matches the listener in method parameters
+        if (subscription && subscription.listener === listener) {
+          subscription.remove();
+        }
+      }
+    }
+  }
+}
+
+export default EventEmitter;

packages/react-native-web/src/vendor/react-native/emitter/EventEmitterWithHolding.js

@@ -0,0 +1,163 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @providesModule EventEmitterWithHolding
+ * @flow
+ */
+'use strict';
+
+import type EmitterSubscription from './EmitterSubscription';
+import type EventEmitter from './EventEmitter';
+import type EventHolder from './EventHolder';
+
+/**
+ * @class EventEmitterWithHolding
+ * @description
+ * An EventEmitterWithHolding decorates an event emitter and enables one to
+ * "hold" or cache events and then have a handler register later to actually
+ * handle them.
+ *
+ * This is separated into its own decorator so that only those who want to use
+ * the holding functionality have to and others can just use an emitter. Since
+ * it implements the emitter interface it can also be combined with anything
+ * that uses an emitter.
+ */
+class EventEmitterWithHolding {
+
+  _emitter: EventEmitter;
+  _eventHolder: EventHolder;
+  _currentEventToken: ?Object;
+  _emittingHeldEvents: boolean;
+
+  /**
+   * @constructor
+   * @param {object} emitter - The object responsible for emitting the actual
+   *   events.
+   * @param {object} holder - The event holder that is responsible for holding
+   *   and then emitting held events.
+   */
+  constructor(emitter: EventEmitter, holder: EventHolder) {
+    this._emitter = emitter;
+    this._eventHolder = holder;
+    this._currentEventToken = null;
+    this._emittingHeldEvents = false;
+  }
+
+  /**
+   * @see EventEmitter#addListener
+   */
+  addListener(eventType: string, listener: Function, context: ?Object) {
+    return this._emitter.addListener(eventType, listener, context);
+  }
+
+  /**
+   * @see EventEmitter#once
+   */
+  once(eventType: string, listener: Function, context: ?Object) {
+    return this._emitter.once(eventType, listener, context);
+  }
+
+  /**
+   * Adds a listener to be invoked when events of the specified type are
+   * emitted. An optional calling context may be provided. The data arguments
+   * emitted will be passed to the listener function. In addition to subscribing
+   * to all subsequent events, this method will also handle any events that have
+   * already been emitted, held, and not released.
+   *
+   * @param {string} eventType - Name of the event to listen to
+   * @param {function} listener - Function to invoke when the specified event is
+   *   emitted
+   * @param {*} context - Optional context object to use when invoking the
+   *   listener
+   *
+   * @example
+   *   emitter.emitAndHold('someEvent', 'abc');
+   *
+   *   emitter.addRetroactiveListener('someEvent', function(message) {
+   *     console.log(message);
+   *   }); // logs 'abc'
+   */
+  addRetroactiveListener(
+    eventType: string, listener: Function, context: ?Object): EmitterSubscription {
+    const subscription = this._emitter.addListener(eventType, listener, context);
+
+    this._emittingHeldEvents = true;
+    this._eventHolder.emitToListener(eventType, listener, context);
+    this._emittingHeldEvents = false;
+
+    return subscription;
+  }
+
+  /**
+   * @see EventEmitter#removeAllListeners
+   */
+  removeAllListeners(eventType: string) {
+    this._emitter.removeAllListeners(eventType);
+  }
+
+  /**
+   * @see EventEmitter#removeCurrentListener
+   */
+  removeCurrentListener() {
+    this._emitter.removeCurrentListener();
+  }
+
+  /**
+   * @see EventEmitter#listeners
+   */
+  listeners(eventType: string) /* TODO: Annotate return type here */ {
+    return this._emitter.listeners(eventType);
+  }
+
+  /**
+   * @see EventEmitter#emit
+   */
+  emit(eventType: string, ...args: any) {
+    this._emitter.emit(eventType, ...args);
+  }
+
+  /**
+   * Emits an event of the given type with the given data, and holds that event
+   * in order to be able to dispatch it to a later subscriber when they say they
+   * want to handle held events.
+   *
+   * @param {string} eventType - Name of the event to emit
+   * @param {...*} Arbitrary arguments to be passed to each registered listener
+   *
+   * @example
+   *   emitter.emitAndHold('someEvent', 'abc');
+   *
+   *   emitter.addRetroactiveListener('someEvent', function(message) {
+   *     console.log(message);
+   *   }); // logs 'abc'
+   */
+  emitAndHold(eventType: string, ...args: any) {
+    this._currentEventToken = this._eventHolder.holdEvent(eventType, ...args);
+    this._emitter.emit(eventType, ...args);
+    this._currentEventToken = null;
+  }
+
+  /**
+   * @see EventHolder#releaseCurrentEvent
+   */
+  releaseCurrentEvent() {
+    if (this._currentEventToken) {
+      this._eventHolder.releaseEvent(this._currentEventToken);
+    } else if (this._emittingHeldEvents) {
+      this._eventHolder.releaseCurrentEvent();
+    }
+  }
+
+  /**
+   * @see EventHolder#releaseEventType
+   * @param {string} eventType
+   */
+  releaseHeldEventType(eventType: string) {
+    this._eventHolder.releaseEventType(eventType);
+  }
+}
+
+export default EventEmitterWithHolding;

packages/react-native-web/src/vendor/react-native/emitter/EventHolder.js

@@ -0,0 +1,119 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @providesModule EventHolder
+ * @flow
+ */
+'use strict';
+
+import invariant from 'fbjs/lib/invariant';
+
+class EventHolder {
+
+  _heldEvents: Object;
+  _currentEventKey: ?Object;
+
+  constructor() {
+    this._heldEvents = {};
+    this._currentEventKey = null;
+  }
+
+  /**
+   * Holds a given event for processing later.
+   *
+   * TODO: Annotate return type better. The structural type of the return here
+   *       is pretty obvious.
+   *
+   * @param {string} eventType - Name of the event to hold and later emit
+   * @param {...*} Arbitrary arguments to be passed to each registered listener
+   * @return {object} Token that can be used to release the held event
+   *
+   * @example
+   *
+   *   holder.holdEvent({someEvent: 'abc'});
+   *
+   *   holder.emitToHandler({
+   *     someEvent: function(data, event) {
+   *       console.log(data);
+   *     }
+   *   }); //logs 'abc'
+   *
+   */
+  holdEvent(eventType: string, ...args: any) {
+    this._heldEvents[eventType] = this._heldEvents[eventType] || [];
+    const eventsOfType = this._heldEvents[eventType];
+    const key = {
+      eventType: eventType,
+      index: eventsOfType.length
+    };
+    eventsOfType.push(args);
+    return key;
+  }
+
+  /**
+   * Emits the held events of the specified type to the given listener.
+   *
+   * @param {?string} eventType - Optional name of the events to replay
+   * @param {function} listener - The listener to which to dispatch the event
+   * @param {?object} context - Optional context object to use when invoking
+   *   the listener
+   */
+  emitToListener(eventType: ?string , listener: Function, context: ?Object) {
+    const eventsOfType = this._heldEvents[eventType];
+    if (!eventsOfType) {
+      return;
+    }
+    const origEventKey = this._currentEventKey;
+    eventsOfType.forEach((/*?array*/ eventHeld, /*number*/ index) => {
+      if (!eventHeld) {
+        return;
+      }
+      this._currentEventKey = {
+        eventType: eventType,
+        index: index
+      };
+      listener.apply(context, eventHeld);
+    });
+    this._currentEventKey = origEventKey;
+  }
+
+  /**
+   * Provides an API that can be called during an eventing cycle to release
+   * the last event that was invoked, so that it is no longer "held".
+   *
+   * If it is called when not inside of an emitting cycle it will throw.
+   *
+   * @throws {Error} When called not during an eventing cycle
+   */
+  releaseCurrentEvent() {
+    invariant(
+      this._currentEventKey !== null,
+      'Not in an emitting cycle; there is no current event'
+    );
+    this._currentEventKey && this.releaseEvent(this._currentEventKey);
+  }
+
+  /**
+   * Releases the event corresponding to the handle that was returned when the
+   * event was first held.
+   *
+   * @param {object} token - The token returned from holdEvent
+   */
+  releaseEvent(token: Object) {
+    delete this._heldEvents[token.eventType][token.index];
+  }
+
+  /**
+   * Releases all events of a certain type.
+   *
+   * @param {string} type
+   */
+  releaseEventType(type: string) {
+    this._heldEvents[type] = [];
+  }
+}
+
+export default EventHolder;

packages/react-native-web/src/vendor/react-native/emitter/EventSubscription.js

@@ -0,0 +1,40 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @providesModule EventSubscription
+ * @flow
+ */
+'use strict';
+
+import type EventSubscriptionVendor from './EventSubscriptionVendor';
+
+/**
+ * EventSubscription represents a subscription to a particular event. It can
+ * remove its own subscription.
+ */
+class EventSubscription {
+
+  eventType: string;
+  key: number;
+  subscriber: EventSubscriptionVendor;
+
+  /**
+   * @param {EventSubscriptionVendor} subscriber the subscriber that controls
+   *   this subscription.
+   */
+  constructor(subscriber: EventSubscriptionVendor) {
+    this.subscriber = subscriber;
+  }
+
+  /**
+   * Removes this subscription from the subscriber that controls it.
+   */
+  remove() {
+    this.subscriber.removeSubscription(this);
+  }
+}
+
+export default EventSubscription;

packages/react-native-web/src/vendor/react-native/emitter/EventSubscriptionVendor.js

@@ -0,0 +1,98 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @providesModule EventSubscriptionVendor
+ * @flow
+ */
+'use strict';
+
+import invariant from 'fbjs/lib/invariant';
+
+import type EventSubscription from './EventSubscription';
+
+/**
+ * EventSubscriptionVendor stores a set of EventSubscriptions that are
+ * subscribed to a particular event type.
+ */
+class EventSubscriptionVendor {
+
+  _subscriptionsForType: Object;
+  _currentSubscription: ?EventSubscription;
+
+  constructor() {
+    this._subscriptionsForType = {};
+    this._currentSubscription = null;
+  }
+
+  /**
+   * Adds a subscription keyed by an event type.
+   *
+   * @param {string} eventType
+   * @param {EventSubscription} subscription
+   */
+  addSubscription(
+    eventType: string, subscription: EventSubscription): EventSubscription {
+    invariant(
+      subscription.subscriber === this,
+      'The subscriber of the subscription is incorrectly set.');
+    if (!this._subscriptionsForType[eventType]) {
+      this._subscriptionsForType[eventType] = [];
+    }
+    const key = this._subscriptionsForType[eventType].length;
+    this._subscriptionsForType[eventType].push(subscription);
+    subscription.eventType = eventType;
+    subscription.key = key;
+    return subscription;
+  }
+
+  /**
+   * Removes a bulk set of the subscriptions.
+   *
+   * @param {?string} eventType - Optional name of the event type whose
+   *   registered supscriptions to remove, if null remove all subscriptions.
+   */
+  removeAllSubscriptions(eventType: ?string) {
+    if (eventType === undefined) {
+      this._subscriptionsForType = {};
+    } else {
+      delete this._subscriptionsForType[eventType];
+    }
+  }
+
+  /**
+   * Removes a specific subscription. Instead of calling this function, call
+   * `subscription.remove()` directly.
+   *
+   * @param {object} subscription
+   */
+  removeSubscription(subscription: Object) {
+    const eventType = subscription.eventType;
+    const key = subscription.key;
+
+    const subscriptionsForType = this._subscriptionsForType[eventType];
+    if (subscriptionsForType) {
+      delete subscriptionsForType[key];
+    }
+  }
+
+  /**
+   * Returns the array of subscriptions that are currently registered for the
+   * given event type.
+   *
+   * Note: This array can be potentially sparse as subscriptions are deleted
+   * from it when they are removed.
+   *
+   * TODO: This returns a nullable array. wat?
+   *
+   * @param {string} eventType
+   * @returns {?array}
+   */
+  getSubscriptionsForType(eventType: string): ?[EventSubscription] {
+   return this._subscriptionsForType[eventType];
+  }
+}
+
+export default EventSubscriptionVendor;

packages/react-native-web/src/vendor/react-native/emitter/EventValidator.js

@@ -0,0 +1,137 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @providesModule EventValidator
+ * @flow
+ */
+'use strict';
+
+const __DEV__ = process.env.NODE_ENV !== 'production';
+
+/**
+ * EventValidator is designed to validate event types to make it easier to catch
+ * common mistakes. It accepts a map of all of the different types of events
+ * that the emitter can emit. Then, if a user attempts to emit an event that is
+ * not one of those specified types the emitter will throw an error. Also, it
+ * provides a relatively simple matcher so that if it thinks that you likely
+ * mistyped the event name it will suggest what you might have meant to type in
+ * the error message.
+ */
+const EventValidator = {
+  /**
+   * @param {Object} emitter - The object responsible for emitting the actual
+   *                             events
+   * @param {Object} types - The collection of valid types that will be used to
+   *                         check for errors
+   * @return {Object} A new emitter with event type validation
+   * @example
+   *   const types = {someEvent: true, anotherEvent: true};
+   *   const emitter = EventValidator.addValidation(emitter, types);
+   */
+  addValidation: function(emitter: Object, types: Object) {
+    const eventTypes = Object.keys(types);
+    const emitterWithValidation = Object.create(emitter);
+
+    Object.assign(emitterWithValidation, {
+      emit: function emit(type, a, b, c, d, e, _) {
+        assertAllowsEventType(type, eventTypes);
+        return emitter.emit.call(this, type, a, b, c, d, e, _);
+      }
+    });
+
+    return emitterWithValidation;
+  }
+};
+
+function assertAllowsEventType(type, allowedTypes) {
+  if (allowedTypes.indexOf(type) === -1) {
+    throw new TypeError(errorMessageFor(type, allowedTypes));
+  }
+}
+
+function errorMessageFor(type, allowedTypes) {
+  let message = 'Unknown event type "' + type + '". ';
+  if (__DEV__) {
+    message += recommendationFor(type, allowedTypes);
+  }
+  message += 'Known event types: ' + allowedTypes.join(', ') + '.';
+  return message;
+}
+
+// Allow for good error messages
+if (__DEV__) {
+  var recommendationFor = function (type, allowedTypes) {
+    const closestTypeRecommendation = closestTypeFor(type, allowedTypes);
+    if (isCloseEnough(closestTypeRecommendation, type)) {
+      return 'Did you mean "' + closestTypeRecommendation.type + '"? ';
+    } else {
+      return '';
+    }
+  };
+
+  var closestTypeFor = function (type, allowedTypes) {
+    const typeRecommendations = allowedTypes.map(
+      typeRecommendationFor.bind(this, type)
+    );
+    return typeRecommendations.sort(recommendationSort)[0];
+  };
+
+  var typeRecommendationFor = function (type, recommendedType) {
+    return {
+      type: recommendedType,
+      distance: damerauLevenshteinDistance(type, recommendedType)
+    };
+  };
+
+  var recommendationSort = function (recommendationA, recommendationB) {
+    if (recommendationA.distance < recommendationB.distance) {
+      return -1;
+    } else if (recommendationA.distance > recommendationB.distance) {
+      return 1;
+    } else {
+      return 0;
+    }
+  };
+
+  var isCloseEnough = function (closestType, actualType) {
+    return (closestType.distance / actualType.length) < 0.334;
+  };
+
+  var damerauLevenshteinDistance = function (a, b) {
+    let i, j;
+    const d = [];
+
+    for (i = 0; i <= a.length; i++) {
+      d[i] = [i];
+    }
+
+    for (j = 1; j <= b.length; j++) {
+      d[0][j] = j;
+    }
+
+    for (i = 1; i <= a.length; i++) {
+      for (j = 1; j <= b.length; j++) {
+        const cost = a.charAt(i - 1) === b.charAt(j - 1) ? 0 : 1;
+
+        d[i][j] = Math.min(
+          d[i - 1][j] + 1,
+          d[i][j - 1] + 1,
+          d[i - 1][j - 1] + cost
+        );
+
+        if (i > 1 && j > 1 &&
+            a.charAt(i - 1) === b.charAt(j - 2) &&
+            a.charAt(i - 2) === b.charAt(j - 1)) {
+          d[i][j] = Math.min(d[i][j], d[i - 2][j - 2] + cost);
+        }
+      }
+    }
+
+    return d[a.length][b.length];
+  };
+}
+
+export default EventValidator;

packages/react-native-web/src/vendor/react-native/emitter/mixInEventEmitter.js

@@ -0,0 +1,137 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @providesModule mixInEventEmitter
+ * @flow
+ */
+'use strict';
+
+import EventEmitter from './EventEmitter';
+import EventEmitterWithHolding from './EventEmitterWithHolding';
+import EventHolder from './EventHolder';
+import EventValidator from './EventValidator';
+
+import invariant from 'fbjs/lib/invariant';
+/* $FlowFixMe(>=0.54.0 site=react_native_oss) This comment suppresses an error
+ * found when Flow v0.54 was deployed. To see the error delete this comment and
+ * run Flow. */
+import keyOf from 'fbjs/lib/keyOf';
+
+import type EmitterSubscription from './EmitterSubscription';
+
+const __DEV__ = process.env.NODE_ENV !== 'production';
+const TYPES_KEY = keyOf({__types: true});
+
+/**
+ * API to setup an object or constructor to be able to emit data events.
+ *
+ * @example
+ * function Dog() { ...dog stuff... }
+ * mixInEventEmitter(Dog, {bark: true});
+ *
+ * var puppy = new Dog();
+ * puppy.addListener('bark', function (volume) {
+ *   console.log('Puppy', this, 'barked at volume:', volume);
+ * });
+ * puppy.emit('bark', 'quiet');
+ * // Puppy <puppy> barked at volume: quiet
+ *
+ *
+ * // A "singleton" object may also be commissioned:
+ *
+ * var Singleton = {};
+ * mixInEventEmitter(Singleton, {lonely: true});
+ * Singleton.emit('lonely', true);
+ */
+function mixInEventEmitter(cls: Function | Object, types: Object) {
+  invariant(types, 'Must supply set of valid event types');
+
+  // If this is a constructor, write to the prototype, otherwise write to the
+  // singleton object.
+  const target = cls.prototype || cls;
+
+  invariant(!target.__eventEmitter, 'An active emitter is already mixed in');
+
+  const ctor = cls.constructor;
+  if (ctor) {
+    invariant(
+      ctor === Object || ctor === Function,
+      'Mix EventEmitter into a class, not an instance'
+    );
+  }
+
+  // Keep track of the provided types, union the types if they already exist,
+  // which allows for prototype subclasses to provide more types.
+  if (target.hasOwnProperty(TYPES_KEY)) {
+    Object.assign(target.__types, types);
+  } else if (target.__types) {
+    target.__types = Object.assign({}, target.__types, types);
+  } else {
+    target.__types = types;
+  }
+  Object.assign(target, EventEmitterMixin);
+}
+
+const EventEmitterMixin = {
+  emit: function(eventType, a, b, c, d, e, _) {
+    return this.__getEventEmitter().emit(eventType, a, b, c, d, e, _);
+  },
+
+  emitAndHold: function(eventType, a, b, c, d, e, _) {
+    return this.__getEventEmitter().emitAndHold(eventType, a, b, c, d, e, _);
+  },
+
+  addListener: function(eventType, listener, context): EmitterSubscription {
+    return this.__getEventEmitter().addListener(eventType, listener, context);
+  },
+
+  once: function(eventType, listener, context) {
+    return this.__getEventEmitter().once(eventType, listener, context);
+  },
+
+  addRetroactiveListener: function(eventType, listener, context) {
+    return this.__getEventEmitter().addRetroactiveListener(
+      eventType,
+      listener,
+      context
+    );
+  },
+
+  addListenerMap: function(listenerMap, context) {
+    return this.__getEventEmitter().addListenerMap(listenerMap, context);
+  },
+
+  addRetroactiveListenerMap: function(listenerMap, context) {
+    return this.__getEventEmitter().addListenerMap(listenerMap, context);
+  },
+
+  removeAllListeners: function() {
+    this.__getEventEmitter().removeAllListeners();
+  },
+
+  removeCurrentListener: function() {
+    this.__getEventEmitter().removeCurrentListener();
+  },
+
+  releaseHeldEventType: function(eventType) {
+    this.__getEventEmitter().releaseHeldEventType(eventType);
+  },
+
+  __getEventEmitter: function() {
+    if (!this.__eventEmitter) {
+      let emitter = new EventEmitter();
+      if (__DEV__) {
+        emitter = EventValidator.addValidation(emitter, this.__types);
+      }
+
+      const holder = new EventHolder();
+      this.__eventEmitter = new EventEmitterWithHolding(emitter, holder);
+    }
+    return this.__eventEmitter;
+  }
+};
+
+export default mixInEventEmitter;