MDL-59688 enrol: Show removed users

When users are automatically removed from the bulk action selection (due to a non-matching enrolment method)
we should show a warning to make it obvious.

lang/en/enrol.php

@@ -139,6 +139,7 @@
 $string['uninstallmigrating'] = 'Migrating "{$a}" enrolments';
 $string['unknowajaxaction'] = 'Unknown action requested';
 $string['unlimitedduration'] = 'Unlimited';
+$string['userremovedfromselectiona'] = 'User "{$a}" was removed from the selection.';
 $string['usersearch'] = 'Search ';
 $string['withselectedusers'] = 'With selected users';
 $string['extremovedaction'] = 'External unenrol action';

user/action_redir.php

@@ -114,6 +114,18 @@
 
     $users = $manager->get_users_enrolments($userids);
 
+    $removed = array_diff($userids, array_keys($users));
+    if (!empty($removed)) {
+        // This manager does not filter by enrolment method - so we can get the removed users details.
+        $removedmanager = new course_enrolment_manager($PAGE, $course);
+        $removedusers = $removedmanager->get_users_enrolments($removed);
+
+        foreach ($removedusers as $removeduser) {
+            $msg = get_string('userremovedfromselectiona', 'enrol', fullname($removeduser));
+            \core\notification::warning($msg);
+        }
+    }
+
     // We may have users from any kind of enrolment, we need to filter for the enrolment plugin matching the bulk action.
     $matchesplugin = function($user) use ($plugin) {
         foreach ($user->enrolments as $enrolment) {
@@ -123,12 +135,14 @@
         }
         return false;
     };
-    $users = array_filter($users, $matchesplugin);
+    $filteredusers = array_filter($users, $matchesplugin);
 
-    if (empty($users)) {
+    if (empty($filteredusers)) {
         redirect($returnurl, get_string('noselectedusers', 'bulkusers'));
     }
 
+    $users = $filteredusers;
+
     // Get the form for the bulk operation.
     $mform = $operation->get_form($PAGE->url, array('users' => $users));
     // If the mform is false then attempt an immediate process. This may be an immediate action that