From d38c3dfc8eaed71eadec85748e253da96cdda90f Mon Sep 17 00:00:00 2001
From: Andrew Nicols <andrew@nicols.co.uk>
Date: Thu, 24 Aug 2023 23:13:35 +0800
Subject: [PATCH] MDL-77917 communication_matrix: Topic must not be null

The Matrix space/room topic must always be a string. We should normalise
this on the way out of the API.
---
 communication/provider/matrix/classes/matrix_rooms.php |  6 +++---
 .../provider/matrix/tests/matrix_rooms_test.php        | 10 ++++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/communication/provider/matrix/classes/matrix_rooms.php b/communication/provider/matrix/classes/matrix_rooms.php
index 2a00f55128d..157351cd352 100644
--- a/communication/provider/matrix/classes/matrix_rooms.php
+++ b/communication/provider/matrix/classes/matrix_rooms.php
@@ -136,9 +136,9 @@ class matrix_rooms {
     /**
      * Get the matrix room topic.
      *
-     * @return string|null
+     * @return string
      */
-    public function get_topic(): ?string {
-        return $this->record->topic;
+    public function get_topic(): string {
+        return $this->record->topic ?? '';
     }
 }
diff --git a/communication/provider/matrix/tests/matrix_rooms_test.php b/communication/provider/matrix/tests/matrix_rooms_test.php
index f7f43c57bf1..7f9788252ba 100644
--- a/communication/provider/matrix/tests/matrix_rooms_test.php
+++ b/communication/provider/matrix/tests/matrix_rooms_test.php
@@ -49,6 +49,16 @@ class matrix_rooms_test extends \advanced_testcase {
     public function test_create_room_record(): void {
         $this->resetAfterTest();
 
+        $room = matrix_rooms::create_room_record(
+            processorid: 10000,
+            topic: null,
+        );
+        $this->assertInstanceOf(matrix_rooms::class, $room);
+        $this->assertEquals(10000, $room->get_processor_id());
+        $this->assertNotNull('', $room->get_topic());
+        $this->assertEquals('', $room->get_topic());
+        $this->assertNull($room->get_room_id());
+
         $room = matrix_rooms::create_room_record(
             processorid: 12345,
             topic: 'The topic of this room is thusly',