MDL-83185 core_courseformat: Refresh cache on group change

* When we add users to a group (or remove them), we should refresh
the course index cache so it stays in sync with what the user
can actually see.

course/format/classes/hook_listener.php

@@ -0,0 +1,55 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+namespace core_courseformat;
+
+use core_group\hook\after_group_membership_added;
+use core_group\hook\after_group_membership_removed;
+
+/**
+ * Hook listener for course format
+ *
+ * @package    core_courseformat
+ * @copyright  2024 Laurent David <[email protected]>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class hook_listener {
+    /**
+     * Add members to group room when a new member is added to the group.
+     *
+     * @param after_group_membership_added $hook The group membership added hook.
+     */
+    public static function add_members_to_group(
+        after_group_membership_added $hook,
+    ): void {
+        $group = $hook->groupinstance;
+        $course = get_course($group->courseid);
+        base::invalidate_all_session_caches_for_course($course);
+    }
+
+    /**
+     * Remove members from the room when a member is removed from group room.
+     *
+     * @param after_group_membership_removed $hook The group membership removed hook.
+     */
+    public static function remove_members_from_group(
+        after_group_membership_removed $hook,
+    ): void {
+        $group = $hook->groupinstance;
+        $course = get_course($group->courseid);
+        base::invalidate_all_session_caches_for_course($course);
+    }
+}

lib/db/hooks.php

@@ -45,6 +45,14 @@ $callbacks = [
         'hook' => \core_group\hook\after_group_membership_removed::class,
         'callback' => \core_communication\hook_listener::class . '::remove_members_from_group_room',
     ],
+    [
+        'hook' => \core_group\hook\after_group_membership_added::class,
+        'callback' => \core_courseformat\hook_listener::class . '::add_members_to_group',
+    ],
+    [
+        'hook' => \core_group\hook\after_group_membership_removed::class,
+        'callback' => \core_courseformat\hook_listener::class . '::remove_members_from_group',
+    ],
     [
         'hook' => \core_course\hook\after_course_created::class,
         'callback' => \core_communication\hook_listener::class . '::create_course_communication',