MDL-84750 course: require user be able to view course participants.

course/externallib.php

@@ -4177,22 +4177,28 @@ class core_course_external extends external_api {
      * @param int $groupid Group id from which the users will be obtained
      * @param bool $onlyactive Whether to return only the active enrolled users or all enrolled users in the course.
      * @return array List of users
-     * @throws invalid_parameter_exception
      */
     public static function get_enrolled_users_by_cmid(int $cmid, int $groupid = 0, bool $onlyactive = false) {
-    global $PAGE;
+        global $PAGE;
+
         $warnings = [];
 
-        self::validate_parameters(self::get_enrolled_users_by_cmid_parameters(), [
-                'cmid' => $cmid,
-                'groupid' => $groupid,
-                'onlyactive' => $onlyactive,
+        [
+            'cmid' => $cmid,
+            'groupid' => $groupid,
+            'onlyactive' => $onlyactive,
+        ] = self::validate_parameters(self::get_enrolled_users_by_cmid_parameters(), [
+            'cmid' => $cmid,
+            'groupid' => $groupid,
+            'onlyactive' => $onlyactive,
         ]);
 
         list($course, $cm) = get_course_and_cm_from_cmid($cmid);
         $coursecontext = context_course::instance($course->id);
         self::validate_context($coursecontext);
 
+        course_require_view_participants($coursecontext);
+
         $enrolledusers = get_enrolled_users($coursecontext, '', $groupid, 'u.*', null, 0, 0, $onlyactive);
 
         $users = array_map(function ($user) use ($PAGE) {

course/tests/externallib_test.php

@@ -3742,6 +3742,12 @@ final class externallib_test extends externallib_advanced_testcase {
 
         $this->assertEquals(2, count($users['users']));
         $this->assertEquals($expectedusers, $users);
+
+        // Prohibit the capability for viewing course participants.
+        $this->unassignUserCapability('moodle/course:viewparticipants', null, null, $course1->id);
+        $this->expectException(required_capability_exception::class);
+        $this->expectExceptionMessage('Sorry, but you do not currently have permissions to do that (View participants)');
+        core_course_external::get_enrolled_users_by_cmid($forum1->cmid);
     }
 
     /**