From 4f4746541e6b538feb6739d1374b3241520b9868 Mon Sep 17 00:00:00 2001
From: Nico Jansen <jansennico@gmail.com>
Date: Mon, 17 Feb 2020 17:16:23 +0100
Subject: [PATCH] fix(client): prevent race condition in clear context

---
 client/karma.js | 59 +++++++++++++++++++++++++++++++------------------
 1 file changed, 38 insertions(+), 21 deletions(-)

diff --git a/client/karma.js b/client/karma.js
index edefcdb14..988824908 100644
--- a/client/karma.js
+++ b/client/karma.js
@@ -1,3 +1,4 @@
+// @ts-check
 var stringify = require('../common/stringify')
 var constant = require('./constants')
 var util = require('../common/util')
@@ -89,8 +90,8 @@ function Karma (socket, iframe, opener, navigator, location, document) {
           childWindow.close()
         }
         childWindow = opener(url)
-      // run context on parent element (client_with_context)
-      // using window.__karma__.scriptUrls to get the html element strings and load them dynamically
+        // run context on parent element (client_with_context)
+        // using window.__karma__.scriptUrls to get the html element strings and load them dynamically
       } else if (url !== 'about:blank') {
         var loadScript = function (idx) {
           if (idx < window.__karma__.scriptUrls.length) {
@@ -120,14 +121,25 @@ function Karma (socket, iframe, opener, navigator, location, document) {
         }
         loadScript(0)
       }
-    // run in iframe
+      // run in iframe
     } else {
       iframe.src = policy.createURL(url)
     }
   }
 
+  this.scheduleExecution = function (execution) {
+    if (reloadingContext) {
+      this.scheduledExecution = execution
+    } else {
+      execution()
+    }
+  }
+
   this.onbeforeunload = function () {
-    if (!reloadingContext) {
+    if (reloadingContext) {
+      self.scheduledExecution && self.scheduledExecution()
+      self.scheduledExecution = undefined
+    } else {
       // TODO(vojta): show what test (with explanation about jasmine.UPDATE_INTERVAL)
       self.error('Some of your tests did a full page reload!')
     }
@@ -259,24 +271,29 @@ function Karma (socket, iframe, opener, navigator, location, document) {
   }
 
   socket.on('execute', function (cfg) {
-    // reset startEmitted and reload the iframe
-    startEmitted = false
-    self.config = cfg
-    // if not clearing context, reloadingContext always true to prevent beforeUnload error
-    reloadingContext = !self.config.clearContext
-    navigateContextTo(constant.CONTEXT_URL)
-
-    if (self.config.clientDisplayNone) {
-      [].forEach.call(document.querySelectorAll('#banner, #browsers'), function (el) {
-        el.style.display = 'none'
-      })
-    }
+    // clearing context can be in progress, make sure to schedule execution after it.
+    // See https://github.com/karma-runner/karma/issues/3424
+    self.scheduleExecution(() => {
+      // reset startEmitted and reload the iframe
+      startEmitted = false
+      self.config = cfg
+
+      // if not clearing context, reloadingContext always true to prevent beforeUnload error
+      reloadingContext = !self.config.clearContext
+      navigateContextTo(constant.CONTEXT_URL)
+
+      if (self.config.clientDisplayNone) {
+        [].forEach.call(document.querySelectorAll('#banner, #browsers'), function (el) {
+          el.style.display = 'none'
+        })
+      }
 
-    // clear the console before run
-    // works only on FF (Safari, Chrome do not allow to clear console from js source)
-    if (window.console && window.console.clear) {
-      window.console.clear()
-    }
+      // clear the console before run
+      // works only on FF (Safari, Chrome do not allow to clear console from js source)
+      if (window.console && window.console.clear) {
+        window.console.clear()
+      }
+    })
   })
   socket.on('stop', function () {
     this.complete()