From c14ce14e3cb80b2d4cb4efea163635e88424b53f Mon Sep 17 00:00:00 2001
From: Tim Lock <tim@netspot.com.au>
Date: Mon, 19 Sep 2016 10:14:07 +0930
Subject: [PATCH] MDL-55979 quiz: Fix error moving question from last page

When moving the last question from the last page to the last slot of the previous page would show the error in the error
log but move successfully.
---
 mod/quiz/classes/structure.php    |  3 ++-
 mod/quiz/tests/structure_test.php | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/mod/quiz/classes/structure.php b/mod/quiz/classes/structure.php
index ba7f3a337fa..aae5c245ac4 100644
--- a/mod/quiz/classes/structure.php
+++ b/mod/quiz/classes/structure.php
@@ -715,7 +715,8 @@ class structure {
         }
 
         $followingslotnumber = $moveafterslotnumber + 1;
-        if ($followingslotnumber == $movingslotnumber) {
+        // Prevent checking against non-existance slot when already at the last slot.
+        if ($followingslotnumber == $movingslotnumber && !$this->is_last_slot_in_quiz($followingslotnumber)) {
             $followingslotnumber += 1;
         }
 
diff --git a/mod/quiz/tests/structure_test.php b/mod/quiz/tests/structure_test.php
index dd13daad623..9874635ee70 100644
--- a/mod/quiz/tests/structure_test.php
+++ b/mod/quiz/tests/structure_test.php
@@ -315,6 +315,24 @@ class mod_quiz_structure_testcase extends advanced_testcase {
             ), $structure);
     }
 
+    public function test_move_last_slot_to_previous_page_emptying_the_last_page() {
+        $quizobj = $this->create_test_quiz(array(
+                array('TF1', 1, 'truefalse'),
+                array('TF2', 2, 'truefalse'),
+            ));
+        $structure = \mod_quiz\structure::create_for_quiz($quizobj);
+
+        $idtomove = $structure->get_question_in_slot(2)->slotid;
+        $idmoveafter = $structure->get_question_in_slot(1)->slotid;
+        $structure->move_slot($idtomove, $idmoveafter, '1');
+
+        $structure = \mod_quiz\structure::create_for_quiz($quizobj);
+        $this->assert_quiz_layout(array(
+                array('TF1', 1, 'truefalse'),
+                array('TF2', 1, 'truefalse'),
+            ), $structure);
+    }
+
     public function test_end_of_one_section_to_start_of_next() {
         $quizobj = $this->create_test_quiz(array(
                 array('TF1', 1, 'truefalse'),