From 1da8d303ef757d2a7bbe2ac5d7dbe6705515db1f Mon Sep 17 00:00:00 2001
From: Ankit Agarwal <ankit@moodle.com>
Date: Tue, 19 Sep 2017 11:27:24 +0530
Subject: [PATCH] MDL-59780 mathjax: Make sure mathjax url doesn't become empty

---
 filter/mathjaxloader/db/upgrade.php | 13 ++++++++++++-
 filter/mathjaxloader/version.php    |  2 +-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/filter/mathjaxloader/db/upgrade.php b/filter/mathjaxloader/db/upgrade.php
index e47f34c467d..29f958cec7d 100644
--- a/filter/mathjaxloader/db/upgrade.php
+++ b/filter/mathjaxloader/db/upgrade.php
@@ -138,7 +138,8 @@ MathJax.Hub.Config({
         // setting. Since it is preferably to always load the secure resource.
 
         $httpurl = get_config('filter_mathjaxloader', 'httpurl');
-        if ($httpurl !== 'http://cdn.mathjax.org/mathjax/2.6-latest/MathJax.js') {
+        if ($httpurl !== 'http://cdn.mathjax.org/mathjax/2.6-latest/MathJax.js' &&
+            $httpurl !== 'http://cdn.mathjax.org/mathjax/2.6.1/MathJax.js') {
             // If the http setting has been changed, we make the admin choose the https setting because
             // it indicates some sort of custom setup. This will be supported by the release notes.
             unset_config('httpsurl', 'filter_mathjaxloader');
@@ -196,5 +197,15 @@ MathJax.Hub.Config({
         upgrade_plugin_savepoint(true, 2016120502, 'filter', 'mathjaxloader');
     }
 
+    if ($oldversion < 2016120503) {
+
+        $httpsurl = get_config('filter_mathjaxloader', 'httpsurl');
+        if (empty($httpsurl)) {
+            // URL is empty, most likely because of bad upgrade path. See MDL-59780.
+            set_config('httpsurl', 'https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js', 'filter_mathjaxloader');
+        }
+        upgrade_plugin_savepoint(true,  2016120503, 'filter', 'mathjaxloader');
+    }
+
     return true;
 }
diff --git a/filter/mathjaxloader/version.php b/filter/mathjaxloader/version.php
index a025359493e..3349371aae1 100644
--- a/filter/mathjaxloader/version.php
+++ b/filter/mathjaxloader/version.php
@@ -24,6 +24,6 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$plugin->version  = 2016120502;
+$plugin->version  = 2016120503;
 $plugin->requires = 2016112900;  // Requires this Moodle version.
 $plugin->component= 'filter_mathjaxloader';