Ticket #34676: 34676.2.patch

src/js/_enqueues/admin/common.js

@@ -1569 +1569 @@
                  * notice. Make sure it gets moved just the first time.
                  */
                 if ( ! $progressDiv.hasClass( 'update-details-moved' ) ) {
-                        $progressDiv.insertAfter( $updateNotice ).addClass( 'update-details-moved' );
+                        $progressDiv.appendTo( $updateNotice ).addClass( 'update-details-moved' );
                 }
 
                 // Toggle the progress div visibility.

src/wp-admin/css/common.css

@@ -554 +554 @@
         margin-left: 0;
 }
 
+.update-php .update-maintenance-start {
+        margin-top: 30px;
+}
+.update-php .update-maintenance-content {
+        border-left: 2px dashed #aaa;
+        padding: 1px 0 20px 20px;
+        margin: -10px 0;
+}
+.update-php .update-maintenance-end {
+        margin-bottom: 30px;
+}
+
 .no-js .widefat thead .check-column input,
 .no-js .widefat tfoot .check-column input {
         display: none;

src/wp-admin/includes/class-bulk-plugin-upgrader-skin.php

@@ -22 +22 @@
                 parent::add_strings();
                 /* translators: 1: name of plugin being updated, 2: number of updating plugin, 3: total number of plugins being updated */
                 $this->upgrader->strings['skin_before_update_header'] = __( 'Updating Plugin %1$s (%2$d/%3$d)' );
+                $this->upgrader->strings['bulk_download']             = __( 'Downloading plugin installers.' );
         }
 
         /**
-         * @param string $title
+         * Outputs copy before workload output.
+         *
+         * @param string $title Title or string identifier to use.
+         *
+         * @return void
          */
         public function before( $title = '' ) {
-                parent::before( $this->plugin_info['Title'] );
+                $title = ( $title === '' ) ? $this->plugin_info['Title'] : $title;
+                parent::before( $title );
         }
 
         /**
-         * @param string $title
+         * Outputs copy after workload output.
+         *
+         * @param string $title Title or string identifier to use.
+         *
+         * @return void
          */
         public function after( $title = '' ) {
-                parent::after( $this->plugin_info['Title'] );
+                $title = ( $title === '' ) ? $this->plugin_info['Title'] : $title;
+                parent::after( $title );
                 $this->decrement_update_count( 'plugin' );
         }
 
         /**
+         * Outputs copy after bulk actions are all done.
+         *
+         * @return void
          */
         public function bulk_footer() {
                 parent::bulk_footer();

src/wp-admin/includes/class-bulk-theme-upgrader-skin.php

@@ -16 +16 @@
  * @see Bulk_Upgrader_Skin
  */
 class Bulk_Theme_Upgrader_Skin extends Bulk_Upgrader_Skin {
-        public $theme_info = array(); // Theme_Upgrader::bulk_upgrade() will fill this in.
+        /**
+         * Theme information, which will be filled by Theme_Upgrader::bulk_upgrade()
+         * @var array
+         */
+        public $theme_info = array();
 
+        /**
+         * Registers strings that will be used.
+         *
+         * @return void
+         */
         public function add_strings() {
                 parent::add_strings();
                 /* translators: 1: name of theme being updated, 2: number of updating themes, 3: total number of themes being updated */
                 $this->upgrader->strings['skin_before_update_header'] = __( 'Updating Theme %1$s (%2$d/%3$d)' );
+                $this->upgrader->strings['bulk_download']             = __( 'Downloading theme installers.' );
         }
 
         /**
-         * @param string $title
+         * Outputs copy before workload output.
+         *
+         * @param string $title Title or string identifier to use.
+         *
+         * @return void
          */
         public function before( $title = '' ) {
-                parent::before( $this->theme_info->display( 'Name' ) );
+                $title = ( $title === '' ) ? $this->theme_info->display( 'Name' ) : $title;
+                parent::before( $title );
         }
 
         /**
-         * @param string $title
+         * Outputs copy after workload output.
+         *
+         * @param string $title Title or string identifier to use.
+         *
+         * @return void
          */
         public function after( $title = '' ) {
-                parent::after( $this->theme_info->display( 'Name' ) );
+                $title = ( $title === '' ) ? $this->theme_info->display( 'Name' ) : $title;
+                parent::after( $title );
                 $this->decrement_update_count( 'theme' );
         }
 
         /**
+         * Outputs copy after bulk actions are all done.
+         *
+         * @return void
          */
         public function bulk_footer() {
                 parent::bulk_footer();

new file src/wp-admin/includes/class-bulk-upgrade-element-base.php

@@ +1 @@
+<?php
+
+/**
+ * Abstract base class for Bulk Upgrade Elements
+ *
+ * @since x.x
+ */
+abstract class WP_Bulk_Upgrade_Element_Base {
+        /**
+         * Is this element already up-to-date
+         *
+         * @var bool
+         */
+        protected $up_to_date = false;
+        /**
+         * Has the package been downloaded
+         *
+         * @var bool
+         */
+        protected $downloaded = false;
+        /**
+         * Was the package unpacked properly
+         *
+         * @var bool
+         */
+        protected $unpacked = false;
+        /**
+         * Has the package been installed
+         *
+         * @var bool
+         */
+        protected $installed = false;
+
+        /**
+         * The verification status of a download
+
+         * @var bool|WP_Error
+         */
+        protected $download_verification_result = false;
+
+        /**
+         * Identifier for this element (source)
+         *
+         * @var mixed
+         */
+        protected $name;
+        /**
+         * Upgrader to use
+         *
+         * @var WP_Upgrader
+         */
+        protected $upgrader;
+
+        /**
+         * Options of current element, used throughout the process
+         *
+         * @var array
+         */
+        protected $options;
+        /**
+         * Info about the current element, used by the upgrader
+         *
+         * @var mixed
+         */
+        protected $info;
+        /**
+         * Name of the download
+         *
+         * @var string
+         */
+        protected $download;
+        /**
+         * Working dir for the unpacked package
+         *
+         * @var string
+         */
+        protected $working_dir;
+
+        /**
+         * Final result of installation (via upgrader)
+         *
+         * @var mixed
+         */
+        protected $result;
+
+        /**
+         * WP_Bulk_Upgrader_Element constructor.
+         *
+         * @param WP_Upgrader $upgrader
+         * @param mixed       $name
+         *
+         * @since x.x
+         * @access public
+         */
+        public function __construct( $name, WP_Upgrader $upgrader ) {
+                $this->name     = $name;
+                $this->upgrader = $upgrader;
+        }
+
+        /**
+         * Retrievs the original identifier data.
+         *
+         * @return mixed
+         *
+         * @since x.x
+         * @access public
+         */
+        public function get_name() {
+                return $this->name;
+        }
+
+        /**
+         * Retrieves the cummulated result of the upgrade.
+         *
+         * @return bool
+         *
+         * @since x.x
+         * @access public
+         */
+        public function get_result() {
+                return isset( $this->result ) ? $this->result : $this->installed;
+        }
+
+        /**
+         * Retrieves the result index for the current result.
+         *
+         * @return bool|int
+         *
+         * @since x.x
+         * @access public
+         */
+        public function get_result_index() {
+                return false;
+        }
+
+        /**
+         * Determines if it is active in the system.
+         *
+         * @return boolean
+         *
+         * @since x.x
+         * @access public
+         */
+        abstract public function is_active();
+
+        /**
+         * Determines if it is downloaded correctly.
+         *
+         * @return bool
+         *
+         * @since x.x
+         * @access public
+         */
+        public function is_downloaded() {
+                return $this->downloaded;
+        }
+
+        /**
+         * Determines if it is unpacked succesfully.
+         *
+         * @return bool
+         *
+         * @since x.x
+         * @access public
+         */
+        public function is_unpacked() {
+                return $this->unpacked;
+        }
+
+        /**
+         * Determines if it is installed succesfully.
+         *
+         * @return bool
+         *
+         * @since x.x
+         * @access public
+         */
+        public function is_installed() {
+                return $this->installed;
+        }
+
+        /**
+         * Determines if it is already up-to-date.
+         *
+         * @return bool
+         *
+         * @since x.x
+         * @access public
+         */
+        public function is_up_to_date() {
+                return $this->up_to_date;
+        }
+
+        /**
+         * Retrieves element info.
+         *
+         * @return mixed
+         *
+         * @since x.x
+         * @access public
+         */
+        public function get_info() {
+                return $this->info;
+        }
+
+        /**
+         * Applies defaults and filter to options.
+         *
+         * @param array $options Options to use.
+         * @retun void
+         *
+         * @since x.x
+         * @access protected
+         */
+        protected function set_options( $options ) {
+                $defaults = array(
+                        'package'                     => '',
+                        // Please always pass this.
+                        'destination'                 => '',
+                        // And this
+                        'clear_destination'           => false,
+                        'abort_if_destination_exists' => true,
+                        // Abort if the Destination directory exists, Pass clear_destination as false please
+                        'clear_working'               => true,
+                        'is_multi'                    => false,
+                        'hook_extra'                  => array()
+                        // Pass any extra $hook_extra args here, this will be passed to any hooked filters.
+                );
+
+                $options = wp_parse_args( $options, $defaults );
+
+                /** This filter is documented in wp-admin/includes/class-wp-upgrader.php */
+                $this->options = apply_filters( 'upgrader_package_options', $options );
+        }
+
+        /**
+         * Download this element.
+         *
+         * @return bool|string|WP_Error
+         *
+         * @since x.x
+         * @access public
+         */
+        public function download() {
+                if ( $this->is_up_to_date() ) {
+                        return false;
+                }
+
+                // Connect to the Filesystem first.
+                $result = $this->upgrader->fs_connect( array( WP_CONTENT_DIR, $this->options['destination'] ) );
+                // Mainly for non-connected filesystem.
+                if ( ! $result || is_wp_error( $result ) ) {
+                        return $result;
+                }
+
+                $this->download_verification_result = true;
+
+                /*
+                 * Download the package (Note, This just returns the filename
+                 * of the file if the package is a local file)
+                 */
+                $result = $this->upgrader->download_package( $this->options['package'], true );
+
+                if ( ! is_wp_error( $result ) ) {
+                        $this->downloaded = true;
+                        $this->download   = $result;
+                } else {
+                        $filename = $result->get_error_data( 'softfail-filename' );
+                        if ( $filename ) {
+                                $this->download_verification_result = $result;
+
+                                $result = $filename;
+
+                                $this->downloaded = true;
+                                $this->download   = $result;
+                        }
+                }
+
+                return $result;
+        }
+
+        /**
+         * Unpacks this element.
+         *
+         * @return bool|string|WP_Error
+         *
+         * @since x.x
+         * @access public
+         */
+        public function unpack() {
+                if ( ! $this->is_downloaded() ) {
+                        return false;
+                }
+
+                // Do not delete a "local" file
+                $delete_package = ( $this->download !== $this->options['package'] );
+
+                // Unzips the file into a temporary directory.
+                $result = $this->upgrader->unpack_package( $this->download, $delete_package );
+                if ( ! is_wp_error( $result ) ) {
+                        $this->unpacked    = true;
+                        $this->working_dir = $result;
+                }
+
+                return $result;
+        }
+
+        /**
+         * Installs this element.
+         *
+         * @return array|bool|WP_Error
+         *
+         * @since x.x
+         * @access public
+         */
+        public function install() {
+                if ( ! $this->is_unpacked() ) {
+                        return false;
+                }
+
+                // With the given options, this installs it to the destination directory.
+                $result = $this->upgrader->install_package( array(
+                        'source'                      => $this->working_dir,
+                        'destination'                 => $this->options['destination'],
+                        'clear_destination'           => $this->options['clear_destination'],
+                        'abort_if_destination_exists' => $this->options['abort_if_destination_exists'],
+                        'clear_working'               => $this->options['clear_working'],
+                        'hook_extra'                  => $this->options['hook_extra']
+                ) );
+
+                $this->result = $this->upgrader->result;
+
+                return $result;
+        }
+
+        /**
+         * Retrieves the verification result status.
+         *
+         * @return bool|WP_Error
+         *
+         * @since  x.x
+         * @access public
+         */
+        public function get_verification_result() {
+                return $this->download_verification_result;
+        }
+}

new file src/wp-admin/includes/class-bulk-upgrade-repository-element-base.php

@@ +1 @@
+<?php
+
+/**
+ * Abstract base class for Bulk Upgrade Elements that are formatted as Plugin/Theme
+ *
+ * @since x.x
+ */
+abstract class WP_Bulk_Upgrade_Repository_Element_Base extends WP_Bulk_Upgrade_Element_Base {
+        /**
+         * Cache for current element type information.
+         *
+         * @var object
+         */
+        protected static $current;
+
+        /**
+         * Current element response information from repository.
+         *
+         * @var object
+         */
+        protected $response;
+
+        /**
+         * Retrieves the result index for the current item.
+         *
+         * @return mixed
+         *
+         * @since  x.x
+         * @access public
+         */
+        public function get_result_index() {
+                return $this->name;
+        }
+
+        /**
+         * Retrieves the current item.
+         *
+         * @return mixed
+         *
+         * @since x.x
+         * @access protected
+         */
+        abstract protected function get_current();
+
+        /**
+         * Retrieves plugin repository response.
+         *
+         * @return bool|object Response from the respository as stdClass
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function get_response() {
+                $current = $this->get_current();
+
+                if ( is_object( $current ) && is_array( $current->response ) ) {
+                        return $this->response = isset( $current->response[ $this->name ] ) ? $current->response[ $this->name ] : false;
+                }
+
+                return false;
+        }
+}

new file src/wp-admin/includes/class-bulk-upgrader-base.php

@@ +1 @@
+<?php
+
+/**
+ * Abstract base class for Bulk Upgrades
+ *
+ * @since x.x
+ */
+abstract class WP_Bulk_Upgrader_Base {
+        /**
+         * Upgrader to use.
+         *
+         * @var WP_Upgrader
+         */
+        protected $upgrader;
+
+        /**
+         * Elements to upgrade.
+         *
+         * @var WP_Bulk_Upgrade_Element_Base[]
+         */
+        protected $elements = array();
+
+        /**
+         * WP_Bulk_Upgrader_Composite constructor.
+         *
+         * @param WP_Upgrader $upgrader     Upgrader to report back to
+         * @param array       $elements     List of elements to be bulked.
+         * @param string      $elementClass Class name to wrap elements in. Extended of WP_Bulk_Upgrader_Element.
+         *
+         * @since  x.x
+         * @access public
+         */
+        public function __construct( WP_Upgrader $upgrader, array $elements, $elementClass ) {
+                if ( ! is_string( $elementClass ) ) {
+                        throw new InvalidArgumentException( 'Expected element class to be string, got ' . gettype( $elementClass ) );
+                }
+
+                if ( ! class_exists( $elementClass ) ) {
+                        throw new InvalidArgumentException( sprintf( 'Element class "%s" does not exist.', $elementClass ) );
+                }
+
+                $this->upgrader = $upgrader;
+
+                if ( array() !== $elements ) {
+                        foreach ( $elements as $element ) {
+                                $this->elements[] = new $elementClass( $element, $upgrader );
+                        }
+                }
+
+                $this->upgrader->update_count   = count( $this->elements );
+                $this->upgrader->update_current = 0;
+        }
+
+        /**
+         * Runs the bulk upgrade.
+         *
+         * @return array List of results.
+         *
+         * @since x.x
+         * @access public
+         */
+        public function run() {
+                $this->upgrader->clean_upgrade_folder();
+
+                $this->check_up_to_date( $this->elements );
+
+                // Get all elements that have an upgrade.
+                $upgradable_elements = $this->get_upgradable_elements( $this->elements );
+
+                // Download and unpack all items with upgrades.
+                $this->prepare_upgrade( $upgradable_elements );
+
+                // On multisite it is hard to determine if a plugin is active on a sub-site or not - assume all are active.
+                if ( is_multisite() ) {
+                        $this->upgrade( $upgradable_elements, true );
+                }
+
+                if ( ! is_multisite() ) {
+                        // Get all non-active elements - these don't need maintenance mode enabled.
+                        $inactive_elements = $this->get_inactive_elements( $upgradable_elements );
+                        if ( $inactive_elements ) {
+                                $this->upgrade( $inactive_elements, false );
+                        }
+
+                        // Get all active elements - these need maintenance mode enabled.
+                        $active_elements = $this->get_active_elements( $upgradable_elements );
+                        if ( $active_elements ) {
+                                $this->upgrade( $active_elements, true );
+                        }
+                }
+
+                $this->upgrader->update_current = false;
+
+                return $this->get_results();
+        }
+
+        /**
+         * Prepare download and unpack before installing.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base[] $elements List of elements to prepare.
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function prepare_upgrade( $elements ) {
+                $skin = $this->get_skin();
+
+                $skin->before( 'bulk_download' );
+                $this->download( $elements );
+                $skin->set_result(true);
+                $skin->after( 'bulk_download' );
+
+                $skin->before( 'bulk_unpack' );
+                $this->unpack( $elements );
+                $skin->after( 'bulk_unpack' );
+        }
+
+        /**
+         * Upgrades a list of elements.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base[] $elements         Elements to upgrade.
+         * @param boolean                        $maintenance_mode Enable maintenance mode.
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function upgrade( $elements, $maintenance_mode ) {
+                if ( $maintenance_mode ) {
+                        $this->upgrader->maintenance_mode( true );
+                }
+
+                $this->install( $elements );
+
+                if ( $maintenance_mode ) {
+                        $this->upgrader->maintenance_mode( false );
+                }
+        }
+
+        /**
+         * Downloads all the elements.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base[] $elements
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function download( array $elements ) {
+                /** @var $element WP_Bulk_Upgrade_Element_Base */
+                foreach ( $elements as $element ) {
+                        $this->set_current_element( $element );
+
+                        $result = $element->download();
+                        if ( is_wp_error( $result ) ) {
+                                $this->show_error( $result, $element );
+                                break;
+                        }
+
+                        if ( is_wp_error( $element->get_verification_result() ) ) {
+                                $this->show_warning( $element->get_verification_result(), $element );
+                        }
+                }
+        }
+
+        /**
+         * Unpacks downloaded elements.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base[] $elements Elements to unpack.
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function unpack( array $elements ) {
+                /** @var $element WP_Bulk_Upgrade_Element_Base */
+                foreach ( $elements as $element ) {
+                        $this->set_current_element( $element );
+
+                        $result = $element->unpack();
+                        if ( is_wp_error( $result ) ) {
+                                $this->show_error( $result, $element );
+                        }
+                }
+        }
+
+        /**
+         * Installs elements.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base[] $elements Elements to install.
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function install( array $elements ) {
+                foreach ( $elements as $element ) {
+                        $this->set_current_element( $element );
+
+                        $skin = $this->get_skin();
+                        $skin->before();
+
+                        $result = $element->install();
+
+                        $skin->set_result( $result );
+                        if ( is_wp_error( $result ) ) {
+                                $skin->error( $result );
+                                $skin->feedback( 'process_failed' );
+                        } else {
+                                // Install succeeded.
+                                $skin->feedback( 'process_success' );
+                        }
+                        $skin->after();
+
+                        if ( is_wp_error( $result ) && $this->abort_on_error() ) {
+                                break;
+                        }
+                }
+
+                $this->clear_current_element();
+        }
+
+        /**
+         * Retrieves the elements that have an upgrade available.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base[] $elements List of elements to filter.
+         *
+         * @return array Filtered list of elements with an upgrade.
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function get_upgradable_elements( array $elements ) {
+                return array_filter( $elements, array( $this, 'is_upgradable' ) );
+        }
+
+        /**
+         * Determines if an element has an update.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base $element Element to check.
+         *
+         * @return bool True if an upgrade is available, otherwise False.
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function is_upgradable( WP_Bulk_Upgrade_Element_Base $element ) {
+                return ! $element->is_up_to_date();
+        }
+
+        /**
+         * Retrieves the elements that are not active.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base[] $elements Elements to check.
+         *
+         * @return array Filtered list of elements that are not active.
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function get_inactive_elements( array $elements ) {
+                return array_filter( $elements, array( $this, 'is_inactive') );
+        }
+
+        /**
+         * Determines if an element is active.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base $element Element to check.
+         *
+         * @return bool True if the element is not active, False otherwise.
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function is_inactive( WP_Bulk_Upgrade_Element_Base $element ) {
+                return ! $element->is_active();
+        }
+
+        /**
+         * Retrieves a list of active elements.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base[] $elements Elements to check.
+         *
+         * @return array Filtered list of elements that are active.
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function get_active_elements( array $elements ) {
+                return array_filter( $elements, array( $this, 'is_active' ) );
+        }
+
+        /**
+         * Determines if an element is active.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base $element Element to check.
+         *
+         * @return bool True if the element is active, False otherwise.
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function is_active( WP_Bulk_Upgrade_Element_Base $element ) {
+                return $element->is_active();
+        }
+
+        /**
+         * Set the current element as active on the upgrader
+         *
+         * @param mixed $element
+         *
+         * @return int Current index.
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function set_current_element( $element ) {
+                $index = array_search( $element, $this->elements, true );
+
+                if ( false === $index ) {
+                        $this->upgrader->update_current = false;
+                }
+
+                if ( false !== $index ) {
+                        $this->upgrader->update_current = $index + 1;
+                }
+
+                return $this->upgrader->update_current;
+        }
+
+        /**
+         * Removes the current element.
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function clear_current_element() {
+                $this->upgrader->update_current = false;
+        }
+
+        /**
+         * Checks if any of the elements is already up to date.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base[] $elements Elements to check.
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function check_up_to_date( array $elements ) {
+                /** @var $element WP_Bulk_Upgrade_Element_Base */
+                foreach ( $elements as $element ) {
+                        if ( $element->is_up_to_date() ) {
+                                $this->set_current_element( $element );
+
+                                $this->handle_up_to_date( $element );
+
+                                $skin = $this->get_skin();
+                                $skin->feedback( 'up_to_date' );
+                                $skin->after();
+                        }
+                }
+        }
+
+        /**
+         * Handles what to do when an element is already up to date.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base $element Relevant element.
+         *
+         * @return void
+         *
+         * @since x.x
+         * @access protected
+         */
+        abstract protected function handle_up_to_date( WP_Bulk_Upgrade_Element_Base $element );
+
+        /**
+         * Retrieves the results of the upgrade process.
+         *
+         * @return array List of results.
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function get_results() {
+                $results = array();
+
+                /** @var $element WP_Bulk_Upgrade_Element_Base */
+                foreach ( $this->elements as $element ) {
+                        $index = $element->get_result_index();
+                        if ( false === $index ) {
+                                $results[] = $element->get_result();
+                        } else {
+                                $results[ $index ] = $element->get_result();
+                        }
+                }
+
+                return $results;
+        }
+
+        /**
+         * Passes an error to the skin.
+         *
+         * @param string                       $error
+         * @param WP_Bulk_Upgrade_Element_Base $element
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function show_error( $error, WP_Bulk_Upgrade_Element_Base $element ) {
+                $this->set_current_element( $element );
+
+                $skin = $this->get_skin();
+                if ( $skin ) {
+                        $skin->error( $error );
+                        $skin->after();
+                }
+        }
+
+        /**
+         * Passes a warning to the skin.
+         *
+         * @param WP_Error                     $warning Warning to show.
+         * @param WP_Bulk_Upgrade_Element_Base $element Relevant element.
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function show_warning( WP_Error $warning, WP_Bulk_Upgrade_Element_Base $element ) {
+                $this->set_current_element( $element );
+
+                $skin = $this->get_skin();
+                if ( $skin ) {
+                        foreach ( $warning->get_error_messages() as $message ) {
+                                if ( $warning->get_error_data() && is_string( $warning->get_error_data() ) ) {
+                                        $skin->feedback( $message . ' ' . esc_html( strip_tags( $warning->get_error_data() ) ) );
+                                } else {
+                                        $skin->feedback( $message );
+                                }
+                        }
+                }
+        }
+
+        /**
+         * Determines if we should abort when encountering an error.
+         *
+         * @return bool
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function abort_on_error() {
+                // Prevent credentials auth screen from displaying multiple times.
+                return true;
+        }
+
+        /**
+         * Shorthand retrieval of upgrader skin.
+         *
+         * @return WP_Upgrader_Skin
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function get_skin() {
+                return $this->upgrader->get_skin();
+        }
+}

src/wp-admin/includes/class-bulk-upgrader-skin.php

@@ -16 +16 @@
  * @see WP_Upgrader_Skin
  */
 class Bulk_Upgrader_Skin extends WP_Upgrader_Skin {
+        /**
+         * Are we in an install/upgrade loop.
+         *
+         * @var bool
+         */
         public $in_loop = false;
+
         /**
+         * Did we encounter an error while installing/upgrading.
+         *
          * @var string|false
          */
         public $error = false;
 
         /**
-         * @param array $args
+         * @param array $args Arguments used for this skin.
          */
         public function __construct( $args = array() ) {
                 $defaults = array(
@@ -36 +44 @@
         }
 
         /**
+         * Register the strings that we need.
+         *
+         * @return void
          */
         public function add_strings() {
                 $this->upgrader->strings['skin_upgrade_start'] = __( 'The update process is starting. This process may take a while on some hosts, so please be patient.' );
@@ -46 +57 @@
                 /* translators: %s: Title of an update */
                 $this->upgrader->strings['skin_update_successful'] = __( '%s updated successfully.' );
                 $this->upgrader->strings['skin_upgrade_end']       = __( 'All updates have been completed.' );
+                $this->upgrader->strings['bulk_download']          = __( 'Downloading items.' );
+                $this->upgrader->strings['bulk_unpack']            = __( 'Unpacking downloaded installers.' );
         }
 
         /**
-         * @param string $string
+         * Outputs feedback.
+         *
+         * @param string $string Text to show.
+         *
+         * @return void
          */
         public function feedback( $string ) {
+                $original_string = $string;
+
                 if ( isset( $this->upgrader->strings[ $string ] ) ) {
                         $string = $this->upgrader->strings[ $string ];
                 }
@@ -65 +84 @@
                                 $string = vsprintf( $string, $args );
                         }
                 }
+
                 if ( empty( $string ) ) {
                         return;
                 }
-                if ( $this->in_loop ) {
-                        echo "$string<br />\n";
+
+                if ( $original_string === 'maintenance_start' ) {
+                        printf( '<p class="update-maintenance-start"><strong>%s</strong></p><div class="update-maintenance-content">', $string );
+                } elseif( $original_string === 'maintenance_end' ) {
+                        printf( '</div><p class="update-maintenance-end"><strong>%s</strong></p>', $string );
                 } else {
-                        echo "<p>$string</p>\n";
+                        if ( $this->in_loop ) {
+                                $string = "$string<br/>";
+                        } else {
+                                $string = "<p>$string</p>";
+                        }
+
+                        echo "$string\n";
                 }
+
+                $this->flush_output();
         }
 
         /**
+         * Outputs nothing, this will be displayed within a iframe.
+         *
+         * @return void
          */
         public function header() {
                 // Nothing, This will be displayed within a iframe.
         }
 
         /**
+         * Outputs nothing, this will be displayed within a iframe.
+         *
+         * @return void
          */
         public function footer() {
                 // Nothing, This will be displayed within a iframe.
         }
 
         /**
-         * @param string|WP_Error $error
+         * Showns an error.
+         *
+         * @param string|WP_Error $error Error that will be shown.
          */
         public function error( $error ) {
                 if ( is_string( $error ) && isset( $this->upgrader->strings[ $error ] ) ) {
@@ -110 +149 @@
         }
 
         /**
+         * Shows the bulk header copy.
+         *
+         * @return void
          */
         public function bulk_header() {
                 $this->feedback( 'skin_upgrade_start' );
         }
 
         /**
+         * Shows the bulk footer copy.
+         *
+         * @return void
          */
         public function bulk_footer() {
                 $this->feedback( 'skin_upgrade_end' );
         }
 
         /**
-         * @param string $title
+         * Shows an header for an element.
+         * side-effect: Flushes the output buffer
+         *
+         * @param string $title Copy or string identifier to use.
+         *
+         * @return void
          */
         public function before( $title = '' ) {
                 $this->in_loop = true;
-                printf( '<h2>' . $this->upgrader->strings['skin_before_update_header'] . ' <span class="spinner waiting-' . $this->upgrader->update_current . '"></span></h2>', $title, $this->upgrader->update_current, $this->upgrader->update_count );
-                echo '<script type="text/javascript">jQuery(\'.waiting-' . esc_js( $this->upgrader->update_current ) . '\').css("display", "inline-block");</script>';
+
+                $format = $this->upgrader->strings['skin_before_update_header'];
+
+                $identifier = $this->upgrader->update_current;
+                if ( isset( $this->upgrader->strings[ $title ] ) ) {
+                        $identifier = $title;
+                        $format = $this->upgrader->strings[ $title ];
+                }
+
+                printf(
+                        '<h2>' . $format . ' <span class="' . esc_attr( 'spinner waiting-' . $identifier ) . '"></span></h2>',
+                        $title,
+                        $this->upgrader->update_current,
+                        $this->upgrader->update_count
+                );
+
+                echo '<script type="text/javascript">jQuery(\'.waiting-' . esc_js( $identifier ) . '\').css("display", "inline-block");</script>';
                 // This progress messages div gets moved via JavaScript when clicking on "Show details.".
-                echo '<div class="update-messages hide-if-js" id="progress-' . esc_attr( $this->upgrader->update_current ) . '"><p>';
+                echo '<div class="update-messages hide-if-js" id="' . esc_attr( 'progress-' . $identifier ) . '"><p>';
                 $this->flush_output();
         }
 
         /**
-         * @param string $title
+         * Shows a footer for an element.
+         * side-effect: Flushes the output buffer
+         *
+         * @param string $title Copy or string identifier to use.
+         *
+         * @return void
          */
         public function after( $title = '' ) {
+                $success_format = $this->upgrader->strings['skin_update_successful'];
+                $error_format = $this->upgrader->strings['skin_update_failed_error'];
+                $failed_format = $this->upgrader->strings['skin_update_failed'];
+
+                $identifier = $this->upgrader->update_current;
+                if ( isset( $this->upgrader->strings[ $title ] ) ) {
+                        $identifier = $title;
+                        $title = $this->upgrader->strings[ $title ];
+
+                        $success_format = '';
+                        $error_format = '%2$s';
+                        $failed_format = '%s';
+                }
+
                 echo '</p></div>';
+
                 if ( $this->error || ! $this->result ) {
                         if ( $this->error ) {
-                                echo '<div class="error"><p>' . sprintf( $this->upgrader->strings['skin_update_failed_error'], $title, '<strong>' . $this->error . '</strong>' ) . '</p></div>';
+                                echo '<div class="error"><p>' . sprintf( $error_format, $title, '<strong>' . $this->error . '</strong>' ) . '</p></div>';
                         } else {
-                                echo '<div class="error"><p>' . sprintf( $this->upgrader->strings['skin_update_failed'], $title ) . '</p></div>';
+                                echo '<div class="error"><p>' . sprintf( $failed_format, $title ) . '</p></div>';
                         }
 
-                        echo '<script type="text/javascript">jQuery(\'#progress-' . esc_js( $this->upgrader->update_current ) . '\').show();</script>';
+                        echo '<script type="text/javascript">jQuery(\'#progress-' . esc_js( $identifier ) . '\').show();</script>';
                 }
+
                 if ( $this->result && ! is_wp_error( $this->result ) ) {
                         if ( ! $this->error ) {
-                                echo '<div class="updated js-update-details" data-update-details="progress-' . esc_attr( $this->upgrader->update_current ) . '">' .
-                                        '<p>' . sprintf( $this->upgrader->strings['skin_update_successful'], $title ) .
+                                echo '<div class="updated js-update-details" data-update-details="' . esc_attr( 'progress-' . $identifier ) . '">' .
+                                        '<p>' . sprintf( $success_format, $title ) .
                                         ' <button type="button" class="hide-if-no-js button-link js-update-details-toggle" aria-expanded="false">' . __( 'Show details.' ) . '</button>' .
                                         '</p></div>';
                         }
@@ -163 +249 @@
         }
 
         /**
+         * Resets the state of this class.
+         *
+         * @return void
          */
         public function reset() {
                 $this->in_loop = false;
@@ -170 +259 @@
         }
 
         /**
+         * Flushes the output buffer.
+         *
+         * @return void
          */
         public function flush_output() {
                 wp_ob_end_flush_all();

new file src/wp-admin/includes/class-plugin-bulk-upgrade-element.php

@@ +1 @@
+<?php
+
+/**
+ * Plugin implementation of the Bulk Upgrade Element
+ *
+ * @since x.x
+ */
+class WP_Plugin_Bulk_Upgrade_Element extends WP_Bulk_Upgrade_Repository_Element_Base {
+        /**
+         * WP_Bulk_Upgrader_Plugin_Element constructor.
+         *
+         * @param string          $plugin   Current plugin
+         * @param Plugin_Upgrader $upgrader Upgrader to use.
+         *
+         * @since  x.x
+         * @access public
+         */
+        public function __construct( $plugin, Plugin_Upgrader $upgrader ) {
+                parent::__construct( $plugin, $upgrader );
+
+                $this->info = get_plugin_data( WP_PLUGIN_DIR . '/' . $plugin, false, true );
+
+                $response = $this->get_response();
+                if ( false === $response ) {
+                        $this->up_to_date = true;
+
+                        return;
+                }
+
+                $options = array(
+                        'package'           => $response->package,
+                        'destination'       => WP_PLUGIN_DIR,
+                        'clear_destination' => true,
+                        'clear_working'     => true,
+                        'is_multi'          => true,
+                        'hook_extra'        => array(
+                                'plugin' => $plugin
+                        )
+                );
+
+                $this->set_options( $options );
+        }
+
+        /**
+         * Determines if this plugin is activated.
+         *
+         * @return bool
+         *
+         * @since  x.x
+         * @access public
+         */
+        public function is_active() {
+                return is_plugin_active( $this->name );
+        }
+
+        /**
+         * Retrieves information for the plugin from the `update_plugins` transient.
+         *
+         * @return mixed
+         *
+         * @since x.x
+         * @access protected
+         */
+        protected function get_current() {
+                if ( ! isset( self::$current ) ) {
+                        self::$current = get_site_transient( 'update_plugins' );
+                }
+
+                return self::$current;
+        }
+}

new file src/wp-admin/includes/class-plugin-bulk-upgrader.php

@@ +1 @@
+<?php
+
+/**
+ * Plugin Bulk Upgrader implementation
+ *
+ * @since x.x
+ */
+class WP_Plugin_Bulk_Upgrader extends WP_Bulk_Upgrader_Base {
+        /**
+         * WP_Plugin_Bulk_Upgrader constructor.
+         *
+         * @param Plugin_Upgrader $upgrader Upgrader to use.
+         * @param array           $elements Elements to use.
+         *
+         * @since x.x
+         * @access public
+         */
+        public function __construct( Plugin_Upgrader $upgrader, array $elements = array() ) {
+                parent::__construct( $upgrader, $elements, 'WP_Plugin_Bulk_Upgrade_Element' );
+        }
+
+        /**
+         * Communicates result to skin.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base $element Relevant element.
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access public
+         */
+        public function handle_up_to_date( WP_Bulk_Upgrade_Element_Base $element ) {
+                $skin = $this->get_skin();
+                if ( $skin instanceof WP_Upgrader_Skin ) {
+                        $skin->set_result( 'up_to_date' );
+                }
+        }
+
+        /**
+         * Communicate plugin info to skin
+         *
+         * @param mixed $element
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function set_current_element( $element ) {
+                parent::set_current_element( $element );
+
+                if ( ! $this->upgrader->update_current ) {
+                        return;
+                }
+
+                $skin = $this->get_skin();
+                $skin->plugin_info = $element->get_info();
+        }
+}

src/wp-admin/includes/class-plugin-upgrader.php

@@ -228 +228 @@
                 $this->bulk = true;
                 $this->upgrade_strings();
 
-                $current = get_site_transient( 'update_plugins' );
-
                 add_filter( 'upgrader_clear_destination', array( $this, 'delete_old_plugin' ), 10, 4 );
 
                 $this->skin->header();
@@ -243 +241 @@
 
                 $this->skin->bulk_header();
 
-                /*
-                 * Only start maintenance mode if:
-                 * - running Multisite and there are one or more plugins specified, OR
-                 * - a plugin with an update available is currently active.
-                 * @TODO: For multisite, maintenance mode should only kick in for individual sites if at all possible.
-                 */
-                $maintenance = ( is_multisite() && ! empty( $plugins ) );
-                foreach ( $plugins as $plugin ) {
-                        $maintenance = $maintenance || ( is_plugin_active( $plugin ) && isset( $current->response[ $plugin ] ) );
-                }
-                if ( $maintenance ) {
-                        $this->maintenance_mode( true );
-                }
-
-                $results = array();
-
-                $this->update_count   = count( $plugins );
-                $this->update_current = 0;
-                foreach ( $plugins as $plugin ) {
-                        $this->update_current++;
-                        $this->skin->plugin_info = get_plugin_data( WP_PLUGIN_DIR . '/' . $plugin, false, true );
-
-                        if ( ! isset( $current->response[ $plugin ] ) ) {
-                                $this->skin->set_result( 'up_to_date' );
-                                $this->skin->before();
-                                $this->skin->feedback( 'up_to_date' );
-                                $this->skin->after();
-                                $results[ $plugin ] = true;
-                                continue;
-                        }
-
-                        // Get the URL to the zip file.
-                        $r = $current->response[ $plugin ];
-
-                        $this->skin->plugin_active = is_plugin_active( $plugin );
-
-                        $result = $this->run(
-                                array(
-                                        'package'           => $r->package,
-                                        'destination'       => WP_PLUGIN_DIR,
-                                        'clear_destination' => true,
-                                        'clear_working'     => true,
-                                        'is_multi'          => true,
-                                        'hook_extra'        => array(
-                                                'plugin' => $plugin,
-                                        ),
-                                )
-                        );
-
-                        $results[ $plugin ] = $this->result;
-
-                        // Prevent credentials auth screen from displaying multiple times
-                        if ( false === $result ) {
-                                break;
-                        }
-                } //end foreach $plugins
-
-                $this->maintenance_mode( false );
+                $plugin_bulk_upgrader = new WP_Plugin_Bulk_Upgrader( $this, $plugins );
+                $results = $plugin_bulk_upgrader->run();
 
                 // Force refresh of plugin update information.
                 wp_clean_plugins_cache( $parsed_args['clear_update_cache'] );

new file src/wp-admin/includes/class-theme-bulk-upgrade-element.php

@@ +1 @@
+<?php
+
+/**
+ * Theme implementation of the Bulk Upgrade Element
+ *
+ * @since x.x
+ */
+class WP_Theme_Bulk_Upgrade_Element extends WP_Bulk_Upgrade_Repository_Element_Base {
+        /**
+         * WP_Bulk_Upgrader_Theme_Element constructor.
+         *
+         * @param string         $theme    Theme to use.
+         * @param Theme_Upgrader $upgrader Upgrader to use.
+         *
+         * @since x.x
+         * @access public
+         */
+        public function __construct( $theme, Theme_Upgrader $upgrader ) {
+                parent::__construct( $theme, $upgrader );
+
+                $this->info = $upgrader->theme_info( $theme );
+
+                $response = $this->get_response();
+                if ( false === $response ) {
+                        $this->up_to_date = true;
+
+                        return;
+                }
+
+                $options = array(
+                        'package'           => $this->response['package'],
+                        'destination'       => get_theme_root( $theme ),
+                        'clear_destination' => true,
+                        'clear_working'     => true,
+                        'is_multi'          => true,
+                        'hook_extra'        => array(
+                                'theme' => $theme
+                        )
+                );
+
+                $this->set_options( $options );
+        }
+
+        /**
+         * Determines if this theme is active.
+         *
+         * @return bool
+         *
+         * @since x.x
+         * @access public
+         */
+        public function is_active() {
+                return $this->name === get_stylesheet() || $this->name === get_template();
+        }
+
+        /**
+         * Retrieves information about the theme from the `update_themes` transient.
+         *
+         * @return mixed
+         *
+         * @since x.x
+         * @access protected
+         */
+        protected function get_current() {
+                if ( ! isset( self::$current ) ) {
+                        self::$current = get_site_transient( 'update_themes' );
+                }
+
+                return self::$current;
+        }
+}

new file src/wp-admin/includes/class-theme-bulk-upgrader.php

@@ +1 @@
+<?php
+
+/**
+ * Theme Bulk Upgrader implementation
+ *
+ * @since x.x
+ */
+class WP_Theme_Bulk_Upgrader extends WP_Bulk_Upgrader_Base {
+        /**
+         * WP_Theme_Bulk_Upgrader constructor.
+         *
+         * @param Theme_Upgrader                 $upgrader Upgrader to use.
+         * @param WP_Bulk_Upgrade_Element_Base[] $elements Elements to use.
+         *
+         * @since  x.x
+         * @access public
+         */
+        public function __construct( Theme_Upgrader $upgrader, array $elements = array() ) {
+                parent::__construct( $upgrader, $elements, 'WP_Theme_Bulk_Upgrade_Element' );
+        }
+
+        /**
+         * Handles what to do for an up-to-date theme.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base $element Element to use.
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access public
+         */
+        public function handle_up_to_date( WP_Bulk_Upgrade_Element_Base $element ) {
+                $skin = $this->get_skin();
+                if ( $skin instanceof WP_Upgrader_Skin ) {
+                        $skin->set_result( true );
+                }
+        }
+
+        /**
+         * Sets the current element on the skin.
+         *
+         * @param WP_Bulk_Upgrade_Element_Base $element Element to set as current.
+         *
+         * @return void
+         *
+         * @since  x.x
+         * @access protected
+         */
+        protected function set_current_element( $element ) {
+                parent::set_current_element( $element );
+
+                if ( ! $this->upgrader->update_current ) {
+                        return;
+                }
+
+                $skin = $this->get_skin();
+                if ( $skin instanceof Bulk_Theme_Upgrader_Skin ) {
+                        $skin->theme_info = $element->get_info();
+                }
+        }
+}

src/wp-admin/includes/class-theme-upgrader.php

@@ -358 +358 @@
 
                 $this->skin->bulk_header();
 
-                // Only start maintenance mode if:
-                // - running Multisite and there are one or more themes specified, OR
-                // - a theme with an update available is currently in use.
-                // @TODO: For multisite, maintenance mode should only kick in for individual sites if at all possible.
-                $maintenance = ( is_multisite() && ! empty( $themes ) );
-                foreach ( $themes as $theme ) {
-                        $maintenance = $maintenance || $theme == get_stylesheet() || $theme == get_template();
-                }
-                if ( $maintenance ) {
-                        $this->maintenance_mode( true );
-                }
-
-                $results = array();
-
-                $this->update_count   = count( $themes );
-                $this->update_current = 0;
-                foreach ( $themes as $theme ) {
-                        $this->update_current++;
-
-                        $this->skin->theme_info = $this->theme_info( $theme );
-
-                        if ( ! isset( $current->response[ $theme ] ) ) {
-                                $this->skin->set_result( true );
-                                $this->skin->before();
-                                $this->skin->feedback( 'up_to_date' );
-                                $this->skin->after();
-                                $results[ $theme ] = true;
-                                continue;
-                        }
-
-                        // Get the URL to the zip file
-                        $r = $current->response[ $theme ];
-
-                        $result = $this->run(
-                                array(
-                                        'package'           => $r['package'],
-                                        'destination'       => get_theme_root( $theme ),
-                                        'clear_destination' => true,
-                                        'clear_working'     => true,
-                                        'is_multi'          => true,
-                                        'hook_extra'        => array(
-                                                'theme' => $theme,
-                                        ),
-                                )
-                        );
-
-                        $results[ $theme ] = $this->result;
-
-                        // Prevent credentials auth screen from displaying multiple times
-                        if ( false === $result ) {
-                                break;
-                        }
-                } //end foreach $plugins
-
-                $this->maintenance_mode( false );
+                $theme_bulk_upgrader = new WP_Theme_Bulk_Upgrader( $this, $themes );
+                $results = $theme_bulk_upgrader->run();
 
                 // Refresh the Theme Update information
                 wp_clean_themes_cache( $parsed_args['clear_update_cache'] );

new file src/wp-admin/includes/class-wp-upgrader-bulk.php

@@ +1 @@
+<?php
+/**
+ * The Bulk handlers for the WordPress Upgrader
+ *
+ * @package    WordPress
+ * @subpackage Upgrader
+ * @since      x.x
+ */
+
+require_once 'class-bulk-upgrade-element-base.php';
+require_once 'class-bulk-upgrade-repository-element-base.php';
+
+require_once 'class-bulk-upgrader-base.php';
+
+require_once 'class-plugin-bulk-upgrade-element.php';
+require_once 'class-plugin-bulk-upgrader.php';
+
+require_once 'class-theme-bulk-upgrade-element.php';
+require_once 'class-theme-bulk-upgrader.php';

src/wp-admin/includes/class-wp-upgrader-skin.php

@@ -15 +15 @@
  */
 class WP_Upgrader_Skin {
 
+        /**
+         * Holds the Upgrader to use.
+         *
+         * @var WP_Upgrader
+         */
         public $upgrader;
         public $done_header = false;
         public $done_footer = false;
@@ -42 +47 @@
         }
 
         /**
-         * @param WP_Upgrader $upgrader
+         * Sets the upgrader to use internally.
+         *
+         * @param WP_Upgrader $upgrader Upgrader to use.
          */
         public function set_upgrader( &$upgrader ) {
                 if ( is_object( $upgrader ) ) {

src/wp-admin/includes/class-wp-upgrader.php

@@ -9 +9 @@
  * @since 2.8.0
  */
 
+/** WP_Upgrader_Bulk class */
+require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader-bulk.php';
+
 /** WP_Upgrader_Skin class */
 require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader-skin.php';
 
@@ -64 +67 @@
          * @since 2.8.0
          * @var Automatic_Upgrader_Skin|WP_Upgrader_Skin $skin
          */
-        public $skin = null;
+        public $skin;
 
         /**
          * The result of the installation.
@@ -120 +123 @@
          *                               instance.
          */
         public function __construct( $skin = null ) {
-                if ( null == $skin ) {
+                if ( $skin === null ) {
                         $this->skin = new WP_Upgrader_Skin();
                 } else {
                         $this->skin = $skin;
@@ -304 +307 @@
 
                 $upgrade_folder = $wp_filesystem->wp_content_dir() . 'upgrade/';
 
-                //Clean up contents of upgrade directory beforehand.
-                $upgrade_files = $wp_filesystem->dirlist( $upgrade_folder );
-                if ( ! empty( $upgrade_files ) ) {
-                        foreach ( $upgrade_files as $file ) {
-                                $wp_filesystem->delete( $upgrade_folder . $file['name'], true );
-                        }
-                }
-
                 // We need a working directory - Strip off any .tmp or .zip suffixes
                 $working_dir = $upgrade_folder . basename( basename( $package, '.tmp' ), '.zip' );
 
@@ -702 +697 @@
                  */
                 $options = apply_filters( 'upgrader_package_options', $options );
 
-                if ( ! $options['is_multi'] ) { // call $this->header separately if running multiple times
-                        $this->skin->header();
-                }
+                $this->skin->header();
 
                 // Connect to the Filesystem first.
                 $res = $this->fs_connect( array( WP_CONTENT_DIR, $options['destination'] ) );
@@ -727 +720 @@
                         return $res;
                 }
 
+                $this->clean_upgrade_folder();
+
                 /*
                  * Download the package (Note, This just returns the filename
                  * of the file if the package is a local file)
@@ -925 +920 @@
                 return delete_option( $lock_name . '.lock' );
         }
 
+        /**
+         * Clears optional remnants of previous upgrades
+         *
+         * @since x.x
+         * @access public
+         *
+         * @global WP_Filesystem_Base $wp_filesystem Subclass
+         */
+        public function clean_upgrade_folder() {
+                /** @var WP_Filesystem_Base $wp_filesystem */
+                global $wp_filesystem;
+
+                //Clean up contents of upgrade directory.
+                $upgrade_folder = $wp_filesystem->wp_content_dir() . 'upgrade/';
+                $upgrade_files  = $wp_filesystem->dirlist( $upgrade_folder );
+                if ( ! empty( $upgrade_files ) ) {
+                        foreach ( $upgrade_files as $file ) {
+                                $wp_filesystem->delete( $upgrade_folder . $file['name'], true );
+                        }
+                }
+        }
+
+        /**
+         * Retrieves the used skin.
+         *
+         * @return WP_Upgrader_Skin The used skin.
+         *
+         * @since  x.x
+         * @access public
+         */
+        public function get_skin() {
+                return $this->skin;
+        }
 }
 
 /** Plugin_Upgrader class */