FolderUpdateFilesystemExtension.php

<?php

/**
 * Class FolderUpdateFilesystemExtension fixes issue silverstripe-framework#4993:
 * Renaming Folders over more than two nested levels fails
 */
class FolderUpdateFilesystemExtension extends DataExtension {

    public function onAfterWrite() {
        $this->enhancedUpdateFilesystem();
    }

    public function onBeforeDelete() {
        $this->enhancedUpdateFilesystem();
    }

    public function enhancedUpdateFilesystem(){
        $oldFilename = $this->owner->Filename;

        // update this and only this Folder
        $this->updateFilesystemWithoutRecursion();

        // ALTERNATIVE IMPLEMENTATION USING DB QUERY
        // now check if database and current object differ
        // note: we cannot use isChanged, as this is true
        // even if the change has not been triggered by updateFilesystem
        //$thisFromDB = DataObject::get_by_id('Folder', $this->owner->ID, false);
        //$needsWrite = ($thisFromDB->Filename != $this->owner->Filename)

        $needsWrite = ($oldFilename != $this->owner->Filename);
        if($needsWrite){
            // in this case the filename has changed due to a changed parent
            // we need to write the change to the db, otherwise the children won't see it
            $this->owner->write();
            // no need to proceed as this method has already been called again by the write above
            return;
        }

        // now call the child's enhancedUpdateFilesystem
        if($this->owner->ID && ($children = $this->owner->AllChildren())) {
            foreach($children as $child) {
                if($child instanceof Folder) {
                    $child->enhancedUpdateFilesystem();
                }
            }
        }
    }

    /**
     * Calls File's implementation of updateFilesystem
     * (this is without a recusive update)
     */
    public function updateFilesystemWithoutRecursion(){
        call_user_func(array($this->owner, 'parent::updateFilesystem'));
    }

}