From c24332383b1bf0f1bd67dcb9a487ee0b4d81d167 Mon Sep 17 00:00:00 2001
From: Ashod Nakashian <ashod.nakashian@collabora.co.uk>
Date: Sat, 3 Oct 2020 14:59:13 -0400
Subject: [PATCH] Handle server unavailability better

This prevents xml parsing errors when the server
is not avialable. In a follow-up patch we will
throw a 'server unavailable' error to better
communicate the issue.
---
 classes/collabora.php | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/classes/collabora.php b/classes/collabora.php
index 278fd6f..032b996 100644
--- a/classes/collabora.php
+++ b/classes/collabora.php
@@ -287,6 +287,11 @@ private function get_discovery_xml() {
             $url = rtrim($baseurl, '/').'/hosting/discovery';
             $curl = new \curl();
             $xml = $curl->get($url);
+            if ($curl->get_errno()) {
+                // $xml possibly contains some error message, which isn't a valid xml.
+                return ''; // TODO: throw exception to avoid causing secondary errors.
+            }
+
             $cache->set($baseurl, $xml);
         }
         return $xml;
@@ -299,8 +304,12 @@ private function get_discovery_xml() {
      * @return string
      */
     private function get_url_from_mimetype($discoveryxml, $mimetype) {
-        $xml = new \SimpleXMLElement($discoveryxml);
-        $app = $xml->xpath("//app[@name='{$mimetype}']");
+        $app = null;
+        if ($discoveryxml) {
+            $xml = new \SimpleXMLElement($discoveryxml);
+            $app = $xml->xpath("//app[@name='{$mimetype}']");
+        }
+
         if (!$app) {
             throw new \moodle_exception('unsupportedtype', 'mod_collabora', '', $mimetype);
         }