From 08344a8c4b7dbe4bdc8e00b1e1dcbdc7c259c01d Mon Sep 17 00:00:00 2001
From: Paul Holden <paulh@moodle.com>
Date: Tue, 22 Aug 2023 09:03:57 +0100
Subject: [PATCH] MDL-79073 question: detect missing context when deleting
 question.

---
 lib/questionlib.php            |  3 ++-
 lib/tests/questionlib_test.php | 27 +++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/lib/questionlib.php b/lib/questionlib.php
index 762b7d30081..736e359a6e6 100644
--- a/lib/questionlib.php
+++ b/lib/questionlib.php
@@ -352,11 +352,12 @@ function question_delete_question($questionid): void {
                    qv.version,
                    qbe.id as entryid,
                    qc.id as categoryid,
-                   qc.contextid as contextid
+                   ctx.id as contextid
               FROM {question} q
               LEFT JOIN {question_versions} qv ON qv.questionid = q.id
               LEFT JOIN {question_bank_entries} qbe ON qbe.id = qv.questionbankentryid
               LEFT JOIN {question_categories} qc ON qc.id = qbe.questioncategoryid
+              LEFT JOIN {context} ctx ON ctx.id = qc.contextid
              WHERE q.id = ?';
     $questiondata = $DB->get_record_sql($sql, [$question->id]);
 
diff --git a/lib/tests/questionlib_test.php b/lib/tests/questionlib_test.php
index 1b93d96d59d..0c0bebc91d2 100644
--- a/lib/tests/questionlib_test.php
+++ b/lib/tests/questionlib_test.php
@@ -322,6 +322,33 @@ class questionlib_test extends \advanced_testcase {
         $this->assertFalse($DB->record_exists('question', ['id' => $q1->id]));
     }
 
+    /**
+     * Test deleting a broken question whose category refers to a missing context
+     */
+    public function test_question_delete_question_missing_context() {
+        global $DB;
+
+        $coursecategory = $this->getDataGenerator()->create_category();
+        $context = $coursecategory->get_context();
+
+        /** @var \core_question_generator $generator */
+        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');
+        $questioncategory = $generator->create_question_category(['contextid' => $context->id]);
+        $question = $generator->create_question('shortanswer', null, ['category' => $questioncategory->id]);
+
+        // Now delete the context, to simulate what happens in old sites where
+        // referential integrity has failed.
+        $DB->delete_records('context', ['id' => $context->id]);
+
+        question_delete_question($question->id);
+
+        $this->assertDebuggingCalled('Deleting question ' . $question->id .
+            ' which is no longer linked to a context. Assuming system context ' .
+            'to avoid errors, but this may mean that some data like ' .
+            'files, tags, are not cleaned up.');
+        $this->assertFalse($DB->record_exists('question', ['id' => $question->id]));
+    }
+
     /**
      * This function tests the question_category_delete_safe function.
      */