MDL-48266 backup: Validate backup_auto_storage config

admin/settings/courses.php

@@ -221,7 +221,7 @@ if ($hassiteconfig or has_any_capability($capabilities, $systemcontext)) {
         2 => new lang_string('storagecourseandexternal', 'backup')
     );
     $temp->add(new admin_setting_configselect('backup/backup_auto_storage', new lang_string('automatedstorage', 'backup'), new lang_string('automatedstoragehelp', 'backup'), 0, $storageoptions));
-    $temp->add(new admin_setting_configdirectory('backup/backup_auto_destination', new lang_string('saveto'), new lang_string('backupsavetohelp'), ''));
+    $temp->add(new admin_setting_special_backup_auto_destination());
     $keepoptoins = array(
         0 => new lang_string('all'), 1 => '1',
         2 => '2',

lang/en/moodle.php

@@ -177,6 +177,7 @@ $string['backupdatenew'] = '  {$a->TAG} is now {$a->weekday}, {$a->mday} {$
 $string['backupdateold'] = '{$a->TAG} was {$a->weekday}, {$a->mday} {$a->month} {$a->year}';
 $string['backupdaterecordtype'] = '<br />{$a->recordtype} - {$a->recordname}<br />';
 $string['backupdetails'] = 'Backup details';
+$string['backuperrorinvaliddestination'] = 'The backup destination folder does not exist or is not writable.';
 $string['backupexecuteathelp'] = 'Choose what time automated backups should run at.';
 $string['backupfailed'] = 'Some of your courses weren\'t saved!!';
 $string['backupfilename'] = 'backup';
@@ -194,7 +195,7 @@ $string['backupnonisowarning'] = 'Warning: this backup is from a non-Unicode ver
 $string['backupnotyetrun'] = 'Automated backup pending';
 $string['backuporiginalname'] = 'Backup name';
 $string['backuproleassignments'] = 'Backup role assignments for these roles';
-$string['backupsavetohelp'] = 'Full path to the directory where you want to save the backup files<br />(leave blank to save in its course default dir)';
+$string['backupsavetohelp'] = 'Full path to the directory where you want to save the backup files';
 $string['backupsitefileshelp'] = 'If enabled then site files used in courses will be included in automated backups';
 $string['backuptakealook'] = 'Please take a look at your backup logs in:
   {$a}';

lib/adminlib.php

@@ -4390,6 +4390,44 @@ class admin_setting_special_backupdays extends admin_setting_configmulticheckbox
     }
 }
 
+/**
+ * Special setting for backup auto destination.
+ *
+ * @package    core
+ * @subpackage admin
+ * @copyright  2014 Frédéric Massart - FMCorz.net
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class admin_setting_special_backup_auto_destination extends admin_setting_configdirectory {
+
+    /**
+     * Calls parent::__construct with specific arguments.
+     */
+    public function __construct() {
+        parent::__construct('backup/backup_auto_destination', new lang_string('saveto'), new lang_string('backupsavetohelp'), '');
+    }
+
+    /**
+     * Check if the directory must be set, depending on backup/backup_auto_storage.
+     *
+     * Note: backup/backup_auto_storage must be specified BEFORE this setting otherwise
+     * there will be conflicts if this validation happens before the other one.
+     *
+     * @param string $data Form data.
+     * @return string Empty when no errors.
+     */
+    public function write_setting($data) {
+        $storage = (int) get_config('backup', 'backup_auto_storage');
+        if ($storage !== 0) {
+            if (empty($data) || !file_exists($data) || !is_dir($data) || !is_writable($data) ) {
+                // The directory must exist and be writable.
+                return get_string('backuperrorinvaliddestination');
+            }
+        }
+        return parent::write_setting($data);
+    }
+}
+
 
 /**
  * Special debug setting