From 7bc88f30c3eadded07dd5b460d1e7cb9342d017c Mon Sep 17 00:00:00 2001
From: Evan You <yyx990803@gmail.com>
Date: Wed, 6 Feb 2019 15:04:24 -0500
Subject: [PATCH] fix: skip microtask fix in Firefix <= 53

fix #9446
---
 src/core/util/env.js                        | 1 +
 src/platforms/web/runtime/modules/events.js | 9 +++++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/core/util/env.js b/src/core/util/env.js
index e89a2fc90..eff1d21dc 100644
--- a/src/core/util/env.js
+++ b/src/core/util/env.js
@@ -15,6 +15,7 @@ export const isAndroid = (UA && UA.indexOf('android') > 0) || (weexPlatform ===
 export const isIOS = (UA && /iphone|ipad|ipod|ios/.test(UA)) || (weexPlatform === 'ios')
 export const isChrome = UA && /chrome\/\d+/.test(UA) && !isEdge
 export const isPhantomJS = UA && /phantomjs/.test(UA)
+export const isFF = UA && UA.match(/firefox\/(\d+)/)
 
 // Firefox has a "watch" function on Object.prototype...
 export const nativeWatch = ({}).watch
diff --git a/src/platforms/web/runtime/modules/events.js b/src/platforms/web/runtime/modules/events.js
index e7a969b64..2721a1fd5 100644
--- a/src/platforms/web/runtime/modules/events.js
+++ b/src/platforms/web/runtime/modules/events.js
@@ -2,7 +2,7 @@
 
 import { isDef, isUndef } from 'shared/util'
 import { updateListeners } from 'core/vdom/helpers/index'
-import { isIE, supportsPassive, isUsingMicroTask } from 'core/util/index'
+import { isIE, isFF, supportsPassive, isUsingMicroTask } from 'core/util/index'
 import { RANGE_TOKEN, CHECKBOX_RADIO_TOKEN } from 'web/compiler/directives/model'
 import { currentFlushTimestamp } from 'core/observer/scheduler'
 
@@ -39,6 +39,11 @@ function createOnceHandler (event, handler, capture) {
   }
 }
 
+// #9446: Firefox <= 53 (in particular, ESR 52) has incorrect Event.timeStamp
+// implementation and does not fire microtasks in between event propagation, so
+// safe to exclude.
+const useMicrotaskFix = isUsingMicroTask && !(isFF && Number(isFF[1]) <= 53)
+
 function add (
   name: string,
   handler: Function,
@@ -51,7 +56,7 @@ function add (
   // the solution is simple: we save the timestamp when a handler is attached,
   // and the handler would only fire if the event passed to it was fired
   // AFTER it was attached.
-  if (isUsingMicroTask) {
+  if (useMicrotaskFix) {
     const attachedTimestamp = currentFlushTimestamp
     const original = handler
     handler = original._wrapper = function (e) {