From 2c16a6bb9d5657dfbf921305d7fba0dda4a2840b Mon Sep 17 00:00:00 2001
From: Christopher Chedeau <vjeuxx@gmail.com>
Date: Fri, 2 Sep 2016 15:27:44 -0700
Subject: [PATCH] Convert CallbackQueue to a class (#7647)

It turns out that flow cannot type `this` with a function constructor + prototype overrides. Turning it to a class makes flow happy and has minimal impact on the output.

In open source, we already use the loose version of the class transform and internally we have one that's outputting even less code if you have `@preventMunge` in the header.

See discussion in https://www.facebook.com/groups/2003630259862046/permalink/2098480820376989/
(cherry picked from commit a70acb37d9dc392b395bd921d90d5488542c2402)
---
 .../shared/stack/event/ReactSyntheticEvent.js |  2 +-
 src/renderers/shared/utils/CallbackQueue.js   | 45 ++++++++++---------
 2 files changed, 24 insertions(+), 23 deletions(-)

diff --git a/src/renderers/shared/stack/event/ReactSyntheticEvent.js b/src/renderers/shared/stack/event/ReactSyntheticEvent.js
index 830344d98f..672e137da1 100644
--- a/src/renderers/shared/stack/event/ReactSyntheticEvent.js
+++ b/src/renderers/shared/stack/event/ReactSyntheticEvent.js
@@ -18,4 +18,4 @@ export type DispatchConfig = any;
 
 export class ReactSyntheticEvent extends SyntheticEvent {
   dispatchConfig: DispatchConfig;
-};
+}
diff --git a/src/renderers/shared/utils/CallbackQueue.js b/src/renderers/shared/utils/CallbackQueue.js
index 167403dc80..8f8e53a8c0 100644
--- a/src/renderers/shared/utils/CallbackQueue.js
+++ b/src/renderers/shared/utils/CallbackQueue.js
@@ -27,12 +27,14 @@ var invariant = require('invariant');
  * @implements PooledClass
  * @internal
  */
-function CallbackQueue() {
-  this._callbacks = null;
-  this._contexts = null;
-}
+class CallbackQueue<T> {
+  _callbacks: ?Array<() => void>;
+  _contexts: ?Array<T>;
 
-Object.assign(CallbackQueue.prototype, {
+  constructor() {
+    this._callbacks = null;
+    this._contexts = null;
+  }
 
   /**
    * Enqueues a callback to be invoked when `notifyAll` is invoked.
@@ -41,12 +43,12 @@ Object.assign(CallbackQueue.prototype, {
    * @param {?object} context Context to call `callback` with.
    * @internal
    */
-  enqueue: function(callback, context) {
+  enqueue(callback: () => void, context: T) {
     this._callbacks = this._callbacks || [];
-    this._contexts = this._contexts || [];
     this._callbacks.push(callback);
+    this._contexts = this._contexts || [];
     this._contexts.push(context);
-  },
+  }
 
   /**
    * Invokes all enqueued callbacks and clears the queue. This is invoked after
@@ -54,10 +56,10 @@ Object.assign(CallbackQueue.prototype, {
    *
    * @internal
    */
-  notifyAll: function() {
+  notifyAll() {
     var callbacks = this._callbacks;
     var contexts = this._contexts;
-    if (callbacks) {
+    if (callbacks && contexts) {
       invariant(
         callbacks.length === contexts.length,
         'Mismatched list of contexts in callback queue'
@@ -70,36 +72,35 @@ Object.assign(CallbackQueue.prototype, {
       callbacks.length = 0;
       contexts.length = 0;
     }
-  },
+  }
 
-  checkpoint: function() {
+  checkpoint() {
     return this._callbacks ? this._callbacks.length : 0;
-  },
+  }
 
-  rollback: function(len) {
-    if (this._callbacks) {
+  rollback(len: number) {
+    if (this._callbacks && this._contexts) {
       this._callbacks.length = len;
       this._contexts.length = len;
     }
-  },
+  }
 
   /**
    * Resets the internal queue.
    *
    * @internal
    */
-  reset: function() {
+  reset() {
     this._callbacks = null;
     this._contexts = null;
-  },
+  }
 
   /**
    * `PooledClass` looks for this.
    */
-  destructor: function() {
+  destructor() {
     this.reset();
-  },
-
-});
+  }
+}
 
 module.exports = PooledClass.addPoolingTo(CallbackQueue);