MDL-85334 quiz: Adds record snapshots to slot deleted event

Ensures critical question data is preserved when a quiz slot is deleted.
This is especially useful when the slot-related information is no longer
available. It adds snapshots for question and random question references
to the event when present.

public/mod/quiz/classes/event/slot_deleted.php

@@ -32,6 +32,8 @@ namespace mod_quiz\event;
  *
  *      - int quizid: the id of the quiz.
  *      - int slotnumber: the slot number in quiz.
+ *      - int questionreferenceid: (optional) the question reference id for the slot.
+ *      - int questionsetreferenceid: (optional) the question set reference id for the slot (if added via random cat).
  * }
  *
  * @package    mod_quiz
@@ -79,6 +81,10 @@ class slot_deleted extends \core\event\base {
         if (!isset($this->other['slotnumber'])) {
             throw new \coding_exception('The \'slotnumber\' value must be set in other.');
         }
+        // At least one of questionreferenceid or questionsetreferenceid must be set.
+        if (!isset($this->other['questionreferenceid']) && !isset($this->other['questionsetreferenceid'])) {
+            throw new \coding_exception('Either \'questionreferenceid\' or \'questionsetreferenceid\' must be set in other.');
+        }
     }
 
     public static function get_objectid_mapping() {
@@ -88,7 +94,8 @@ class slot_deleted extends \core\event\base {
     public static function get_other_mapping() {
         $othermapped = [];
         $othermapped['quizid'] = ['db' => 'quiz', 'restore' => 'quiz'];
-
+        $othermapped['questionreferenceid'] = ['db' => 'question_references', 'restore' => 'question_references'];
+        $othermapped['questionsetreferenceid'] = ['db' => 'question_set_references', 'restore' => 'question_set_references'];
         return $othermapped;
     }
 }

public/mod/quiz/classes/structure.php

@@ -1096,7 +1096,9 @@ class structure {
 
         $this->refresh_page_numbers_and_update_db();
 
-        $trans->allow_commit();
+        // Safely extract reference IDs if available.
+        $questionreferenceid = $questionreference->id ?? null;
+        $questionsetreferenceid = $questionsetreference->id ?? null;
 
         // Log slot deleted event.
         $event = \mod_quiz\event\slot_deleted::create([
@@ -1105,9 +1107,22 @@ class structure {
             'other' => [
                 'quizid' => $this->get_quizid(),
                 'slotnumber' => $slotnumber,
-            ]
+                'questionreferenceid' => $questionreferenceid,
+                'questionsetreferenceid' => $questionsetreferenceid,
+            ],
         ]);
+        $event->add_record_snapshot('quiz_slots', $slot);
+
+        // Add snapshots for question and random question references when available.
+        if ($questionreference) {
+            $event->add_record_snapshot('question_references', $questionreference);
+        }
+        if ($questionsetreference) {
+            $event->add_record_snapshot('question_set_references', $questionsetreference);
+        }
+
         $event->trigger();
+        $trans->allow_commit();
     }
 
     /**

public/mod/quiz/tests/event/events_test.php

@@ -1190,7 +1190,8 @@ final class events_test extends \advanced_testcase {
             'other' => [
                 'quizid' => $quizobj->get_quizid(),
                 'slotnumber' => 1,
-            ]
+                'questionreferenceid' => 2,
+            ],
         ];
         $event = \mod_quiz\event\slot_deleted::create($params);
 
@@ -1203,9 +1204,30 @@ final class events_test extends \advanced_testcase {
         // Check that the event data is valid.
         $this->assertInstanceOf('\mod_quiz\event\slot_deleted', $event);
         $this->assertEquals(context_module::instance($quizobj->get_cmid()), $event->get_context());
+        $this->assertEquals(2, $event->other['questionreferenceid']);
         $this->assertEventContextNotUsed($event);
     }
 
+    /**
+     * Test validation failure when neither questionreferenceid nor questionsetreferenceid is provided.
+     */
+    public function test_slot_deleted_no_questionreferenceids(): void {
+        $quizobj = $this->prepare_quiz();
+
+        $params = [
+            'objectid' => 1,
+            'context' => \context_module::instance($quizobj->get_cmid()),
+            'other' => [
+                'quizid' => $quizobj->get_quizid(),
+                'slotnumber' => 1,
+            ],
+        ];
+
+        $this->expectException(\coding_exception::class);
+        $this->expectExceptionMessage('Either \'questionreferenceid\' or \'questionsetreferenceid\' must be set in other.');
+        slot_deleted::create($params);
+    }
+
     /**
      * Test the slot mark updated event.
      *

public/mod/quiz/tests/structure_test.php

@@ -653,8 +653,36 @@ final class structure_test extends \advanced_testcase {
         ]);
         $structure = structure::create_for_quiz($quizobj);
 
+        // Set up event monitoring.
+        $sink = $this->redirectEvents();
+
         $structure->remove_slot(2);
 
+        // Get the event.
+        $events = $sink->get_events();
+        $sink->close();
+        $this->assertCount(1, $events);
+        $event = reset($events);
+
+        // Verify it's the right type of event.
+        $this->assertInstanceOf(\mod_quiz\event\slot_deleted::class, $event);
+
+        // Get the quiz_slot snapshot.
+        $slotid = $event->objectid;
+        $quizslotsnapshot = $event->get_record_snapshot('quiz_slots', $slotid);
+        $this->assertNotNull($quizslotsnapshot);
+
+        // Get the snapshot for question_references.
+        $questionreference = $event->other['questionreferenceid'];
+        if ($questionreference) {
+            $qreferencesnapshot = $event->get_record_snapshot('question_references', $questionreference);
+            $this->assertNotNull($qreferencesnapshot);
+        }
+
+        // Should NOT have the snapshot for question_set_references.
+        $questionsetreference = $event->other['questionsetreferenceid'];
+        $this->assertNull($questionsetreference);
+
         $structure = structure::create_for_quiz($quizobj);
         $this->assert_quiz_layout([
                 ['TF1', 1, 'truefalse'],
@@ -684,10 +712,38 @@ final class structure_test extends \advanced_testcase {
                  WHERE qs.quizid = ?
                    AND qsr.component = ?
                    AND qsr.questionarea = ?';
+
         $randomq = $DB->get_record_sql($sql, [$quizobj->get_quizid(), 'mod_quiz', 'slot']);
+        // Set up event monitoring.
+        $sink = $this->redirectEvents();
 
         $structure->remove_slot(2);
 
+        // Get the event.
+        $events = $sink->get_events();
+        $sink->close();
+        $this->assertCount(1, $events);
+        $event = reset($events);
+
+        // Verify it's the right type of event.
+        $this->assertInstanceOf(\mod_quiz\event\slot_deleted::class, $event);
+
+        // Get the quiz_slot snapshot.
+        $slotid = $event->objectid;
+        $quizslotsnapshot = $event->get_record_snapshot('quiz_slots', $slotid);
+        $this->assertNotNull($quizslotsnapshot);
+
+        // Should NOT have the snapshot for question_references.
+        $questionreference = $event->other['questionreferenceid'];
+        $this->assertNull($questionreference);
+
+        // Get the snapshot for question_set_references.
+        $questionsetreference = $event->other['questionsetreferenceid'];
+        if ($questionsetreference) {
+            $qsetreferencesnapshot = $event->get_record_snapshot('question_set_references', $questionsetreference);
+            $this->assertNotNull($qsetreferencesnapshot);
+        }
+
         $structure = structure::create_for_quiz($quizobj);
         $this->assert_quiz_layout([
                 ['TF1', 1, 'truefalse'],