From 7ab17e5ef30d9b2fc4d639972855bb8f2074ef7a Mon Sep 17 00:00:00 2001
From: Nick Lockwood <nicklockwood@fb.com>
Date: Wed, 2 Dec 2015 09:05:39 -0800
Subject: [PATCH] Fix for long press state transition error in Touchable.js

Summary:
public

This diff fixes an occasional JS exception thrown by Touchable.js when it attempts to transitions to the RESPONDER_ACTIVE_LONG_PRESS_IN state from the RESPONDER_INACTIVE_PRESS_IN state.

Although I wasn't able to reproduce the error while testing, I was able to identify the likely cause: the LONG_PRESS_DETECTED state transition is triggered by a timer that is started on touch-down. This timer should be cancelled if the gesture is interrupted, however I identified a code path where the state can be changed to RESPONDER_INACTIVE_PRESS_IN without the longPressDelayTimeout being cancelled.

To fix this, I've added some logic to cancel the timer in that case. I've also added a test for the error scenario that will display a redbox in __DEV__ mode, but will fail gracefully in production mode.

Reviewed By: jingc

Differential Revision: D2709750

fb-gh-sync-id: aeea1a31de5e92eb394c2ea177f556b131d50790
---
 Libraries/Components/Touchable/Touchable.js | 24 ++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/Libraries/Components/Touchable/Touchable.js b/Libraries/Components/Touchable/Touchable.js
index 0a2f554c4..0493311c5 100644
--- a/Libraries/Components/Touchable/Touchable.js
+++ b/Libraries/Components/Touchable/Touchable.js
@@ -456,6 +456,11 @@ var TouchableMixin = {
           pressExpandBottom;
     if (isTouchWithinActive) {
       this._receiveSignal(Signals.ENTER_PRESS_RECT, e);
+      var curState = this.state.touchable.touchState;
+      if (curState === States.RESPONDER_INACTIVE_PRESS_IN) {
+        // fix for t7967420
+        this._cancelLongPressDelayTimeout();
+      }
     } else {
       this._cancelLongPressDelayTimeout();
       this._receiveSignal(Signals.LEAVE_PRESS_RECT, e);
@@ -564,7 +569,20 @@ var TouchableMixin = {
 
   _handleLongDelay: function(e) {
     this.longPressDelayTimeout = null;
-    this._receiveSignal(Signals.LONG_PRESS_DETECTED, e);
+    var curState = this.state.touchable.touchState;
+    if (curState !== States.RESPONDER_ACTIVE_PRESS_IN &&
+        curState !== States.RESPONDER_ACTIVE_LONG_PRESS_IN) {
+      if (__DEV__) {
+        throw new Error(
+          'Attempted to transition from state `' + curState + '` to `' +
+          States.RESPONDER_ACTIVE_LONG_PRESS_IN + '`, which is not supported. ' +
+          'This is most likely due to `Touchable.longPressDelayTimeout` not ' +
+          'being cancelled.'
+        );  
+      } 
+    } else {
+      this._receiveSignal(Signals.LONG_PRESS_DETECTED, e);
+    }
   },
 
   /**
@@ -577,13 +595,13 @@ var TouchableMixin = {
    */
   _receiveSignal: function(signal, e) {
     var curState = this.state.touchable.touchState;
-    if (!(Transitions[curState] && Transitions[curState][signal])) {
+    var nextState = Transitions[curState] && Transitions[curState][signal];
+    if (!nextState) {
       throw new Error(
         'Unrecognized signal `' + signal + '` or state `' + curState +
         '` for Touchable responder `' + this.state.touchable.responderID + '`'
       );
     }
-    var nextState = Transitions[curState][signal];
     if (nextState === States.ERROR) {
       throw new Error(
         'Touchable cannot transition from `' + curState + '` to `' + signal +