Merge branch 'MDL-77912' of https://github.com/timhunt/moodle

question/type/multichoice/questiontype.php

@@ -244,6 +244,13 @@ public function get_random_guess_score($questiondata) {
             return null;
         }
 
+        if (empty($questiondata->options->answers)) {
+            // A multi-choice question with no choices is senseless,
+            // but, seemingly, it can happen (presumably as a side-effect of bugs).
+            // Therefore, ensure it does not lead to errors here.
+            return null;
+        }
+
         // Single choice questions - average choice fraction.
         $totalfraction = 0;
         foreach ($questiondata->options->answers as $answer) {

question/type/multichoice/tests/question_type_test.php

@@ -31,9 +31,10 @@
 /**
  * Unit tests for the multiple choice question definition class.
  *
- * @package    qtype_multichoice
- * @copyright  2009 The Open University
- * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ * @package   qtype_multichoice
+ * @copyright 2009 The Open University
+ * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ * @covers    \qtype_multichoice
  */
 class question_type_test extends \advanced_testcase {
     protected $qtype;
@@ -72,6 +73,12 @@ public function test_get_random_guess_score() {
         $this->assertEquals(0.5, $this->qtype->get_random_guess_score($q));
     }
 
+    public function test_get_random_guess_score_broken_question() {
+        $q = $this->get_test_question_data();
+        $q->options->answers = [];
+        $this->assertNull($this->qtype->get_random_guess_score($q));
+    }
+
     public function test_get_random_guess_score_multi() {
         $q = $this->get_test_question_data();
         $q->options->single = false;