Bug 1736843: recreate the sessions dirs when clear_all_caches deletes them

when calling clear_all_caches(true), the dataroot/sessions
directories will be deleted
we recreate them again at that moment instead of
waiting until the Session checks

behatnotneeded

Change-Id: I1ea2318cda4743d4908f5cb51990b02aa385a1ea

htdocs/auth/session.php

@@ -123,25 +123,51 @@ class Session {
                 // Attempt to create session directories
                 if (!is_dir("$sessionpath/0")) {
                     // Create three levels of directories, named 0-9, a-f
-                    $characters = array('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f');
-                    if (version_compare(PHP_VERSION, '7.1.0') >= 0) {
-                        $characters = array_merge($characters, array('g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
-                                                                     'o', 'p', 'q', 'r', 's', 't', 'u', 'v'));
-                    }
-                    foreach ($characters as $c1) {
-                        check_dir_exists("$sessionpath/$c1");
-                        foreach ($characters as $c2) {
-                            check_dir_exists("$sessionpath/$c1/$c2");
+                    Session::create_directory_levels($sessionpath);
+                }
+                break;
+            default:
+                throw new ConfigSanityException(get_string('wrongsessionhandle', 'error', get_config('sessionhandler')));
+        }
+    }
+
+    public static function create_directory_levels($sessionpath) {
+        $status = true;
+
+        if (check_dir_exists($sessionpath)) {
+            // Create three levels of directories, named 0-9, a-f
+            $characters = array('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f');
+            if (version_compare(PHP_VERSION, '7.1.0') >= 0) {
+                $characters = array_merge($characters, array('g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
+                                                             'o', 'p', 'q', 'r', 's', 't', 'u', 'v'));
+            }
+            foreach ($characters as $c1) {
+                if (check_dir_exists("$sessionpath/$c1")) {
+                    foreach ($characters as $c2) {
+                        if (check_dir_exists("$sessionpath/$c1/$c2")) {
                             foreach ($characters as $c3) {
-                                check_dir_exists("$sessionpath/$c1/$c2/$c3");
+                                if (!check_dir_exists("$sessionpath/$c1/$c2/$c3")) {
+                                    $status = false;
+                                    break(3);
+                                }
                             }
                         }
+                        else {
+                            $status = false;
+                            break(2);
+                        }
                     }
                 }
-                break;
-            default:
-                throw new ConfigSanityException(get_string('wrongsessionhandle', 'error', get_config('sessionhandler')));
+                else {
+                    $status = false;
+                    break;
+                }
+            }
+        }
+        else {
+            $status = false;
         }
+        return $status;
     }
 
     /**

htdocs/lib/mahara.php

@@ -5125,9 +5125,8 @@ function clear_all_caches($clearsessiondirs = false) {
 
         if ($clearsessiondirs) {
             $session_dir = get_config('dataroot') . 'sessions';
-            if (check_dir_exists($session_dir) && !rmdirr($session_dir)) {
-                throw new SystemException('Can not remove session directory ' . $session_dir);
-            }
+            rmdirr($session_dir);
+            Session::create_directory_levels($session_dir);
         }
 
         clearstatcache();

htdocs/lib/upgrade.php

@@ -595,43 +595,9 @@ function upgrade_plugin($upgrade) {
 }
 
 function core_postinst() {
-    $status = true;
-
     // Attempt to create session directories
     $sessionpath = get_config('sessionpath');
-    if (check_dir_exists($sessionpath)) {
-        // Create three levels of directories, named 0-9, a-f
-        $characters = array('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f');
-        if (version_compare(PHP_VERSION, '7.1.0') >= 0) {
-            $characters = array_merge($characters, array('g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
-                                                         'o', 'p', 'q', 'r', 's', 't', 'u', 'v'));
-        }
-        foreach ($characters as $c1) {
-            if (check_dir_exists("$sessionpath/$c1")) {
-                foreach ($characters as $c2) {
-                    if (check_dir_exists("$sessionpath/$c1/$c2")) {
-                        foreach ($characters as $c3) {
-                            if (!check_dir_exists("$sessionpath/$c1/$c2/$c3")) {
-                                $status = false;
-                                break(3);
-                            }
-                        }
-                    }
-                    else {
-                        $status = false;
-                        break(2);
-                    }
-                }
-            }
-            else {
-                $status = false;
-                break;
-            }
-        }
-    }
-    else {
-        $status = false;
-    }
+    $status = Session::create_directory_levels($sessionpath);
 
     $now = db_format_timestamp(time());
     // Set default search plugin