]> scripts.mit.edu Git - autoinstalls/wordpress.git/blobdiff - wp-admin/includes/class-wp-upgrader.php
WordPress 4.4.1-scripts
[autoinstalls/wordpress.git] / wp-admin / includes / class-wp-upgrader.php
index 6db2c2772573b182e36c94933b425a5d6454b73c..d3abd8eab467ea4426953a0385130c1ff46fb211 100644 (file)
@@ -1,10 +1,10 @@
 <?php
 /**
- * A File upgrader class for WordPress.
+ * Upgrade API: WP_Upgrader, Plugin_Upgrader, Theme_Upgrader, Language_Pack_Upgrader,
+ * Core_Upgrader, File_Upload_Upgrader, and WP_Automatic_Updater classes
  *
- * This set of classes are designed to be used to upgrade/install a local set of files on the filesystem via the Filesystem Abstraction classes.
- *
- * @link http://trac.wordpress.org/ticket/7875 consolidate plugin/theme/core upgrade/install functions
+ * This set of classes are designed to be used to upgrade/install a local set of files
+ * on the filesystem via the Filesystem Abstraction classes.
  *
  * @package WordPress
  * @subpackage Upgrader
 require ABSPATH . 'wp-admin/includes/class-wp-upgrader-skins.php';
 
 /**
- * WordPress Upgrader class for Upgrading/Installing a local set of files via the Filesystem Abstraction classes from a Zip file.
+ * Core class used for upgrading/installing a local set of files via
+ * the Filesystem Abstraction classes from a Zip file.
  *
- * @package WordPress
- * @subpackage Upgrader
  * @since 2.8.0
  */
 class WP_Upgrader {
-       var $strings = array();
-       var $skin = null;
-       var $result = array();
 
-       function __construct($skin = null) {
+       /**
+        * The error/notification strings used to update the user on the progress.
+        *
+        * @since 2.8.0
+        * @access public
+        * @var string $strings
+        */
+       public $strings = array();
+
+       /**
+        * The upgrader skin being used.
+        *
+        * @since 2.8.0
+        * @access public
+        * @var WP_Upgrader_Skin $skin
+        */
+       public $skin = null;
+
+       /**
+        * The result of the installation.
+        *
+        * This is set by {@see WP_Upgrader::install_package()}, only when the package is installed
+        * successfully. It will then be an array, unless a {@see WP_Error} is returned by the
+        * {@see 'upgrader_post_install'} filter. In that case, the `WP_Error` will be assigned to
+        * it.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @var WP_Error|array $result {
+        *      @type string $source             The full path to the source the files were installed from.
+        *      @type string $source_files       List of all the files in the source directory.
+        *      @type string $destination        The full path to the install destination folder.
+        *      @type string $destination_name   The name of the destination folder, or empty if `$destination`
+        *                                       and `$local_destination` are the same.
+        *      @type string $local_destination  The full local path to the destination folder. This is usually
+        *                                       the same as `$destination`.
+        *      @type string $remote_destination The full remote path to the destination folder
+        *                                       (i.e., from `$wp_filesystem`).
+        *      @type bool   $clear_destination  Whether the destination folder was cleared.
+        * }
+        */
+       public $result = array();
+
+       /**
+        * The total number of updates being performed.
+        *
+        * Set by the bulk update methods.
+        *
+        * @since 3.0.0
+        * @access public
+        * @var int $update_count
+        */
+       public $update_count = 0;
+
+       /**
+        * The current update if multiple updates are being performed.
+        *
+        * Used by the bulk update methods, and incremented for each update.
+        *
+        * @since 3.0.0
+        * @access public
+        * @var int
+        */
+       public $update_current = 0;
+
+       /**
+        * Construct the upgrader with a skin.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @param WP_Upgrader_Skin $skin The upgrader skin to use. Default is a {@see WP_Upgrader_Skin}
+        *                               instance.
+        */
+       public function __construct( $skin = null ) {
                if ( null == $skin )
                        $this->skin = new WP_Upgrader_Skin();
                else
                        $this->skin = $skin;
        }
 
-       function init() {
+       /**
+        * Initialize the upgrader.
+        *
+        * This will set the relationship between the skin being used and this upgrader,
+        * and also add the generic strings to `WP_Upgrader::$strings`.
+        *
+        * @since 2.8.0
+        * @access public
+        */
+       public function init() {
                $this->skin->set_upgrader($this);
                $this->generic_strings();
        }
 
-       function generic_strings() {
+       /**
+        * Add the generic strings to WP_Upgrader::$strings.
+        *
+        * @since 2.8.0
+        * @access public
+        */
+       public function generic_strings() {
                $this->strings['bad_request'] = __('Invalid Data provided.');
                $this->strings['fs_unavailable'] = __('Could not access filesystem.');
                $this->strings['fs_error'] = __('Filesystem error.');
@@ -54,22 +140,40 @@ class WP_Upgrader {
                $this->strings['folder_exists'] = __('Destination folder already exists.');
                $this->strings['mkdir_failed'] = __('Could not create directory.');
                $this->strings['incompatible_archive'] = __('The package could not be installed.');
+               $this->strings['files_not_writable'] = __( 'The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.' );
 
                $this->strings['maintenance_start'] = __('Enabling Maintenance mode&#8230;');
                $this->strings['maintenance_end'] = __('Disabling Maintenance mode&#8230;');
        }
 
-       function fs_connect( $directories = array() ) {
+       /**
+        * Connect to the filesystem.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param array $directories                  Optional. A list of directories. If any of these do
+        *                                            not exist, a {@see WP_Error} object will be returned.
+        *                                            Default empty array.
+        * @param bool  $allow_relaxed_file_ownership Whether to allow relaxed file ownership.
+        *                                            Default false.
+        * @return bool|WP_Error True if able to connect, false or a {@see WP_Error} otherwise.
+        */
+       public function fs_connect( $directories = array(), $allow_relaxed_file_ownership = false ) {
                global $wp_filesystem;
 
-               if ( false === ($credentials = $this->skin->request_filesystem_credentials()) )
+               if ( false === ( $credentials = $this->skin->request_filesystem_credentials( false, $directories[0], $allow_relaxed_file_ownership ) ) ) {
                        return false;
+               }
 
-               if ( ! WP_Filesystem($credentials) ) {
+               if ( ! WP_Filesystem( $credentials, $directories[0], $allow_relaxed_file_ownership ) ) {
                        $error = true;
                        if ( is_object($wp_filesystem) && $wp_filesystem->errors->get_error_code() )
                                $error = $wp_filesystem->errors;
-                       $this->skin->request_filesystem_credentials($error); //Failed to connect, Error and request again
+                       // Failed to connect, Error and request again
+                       $this->skin->request_filesystem_credentials( $error, $directories[0], $allow_relaxed_file_ownership );
                        return false;
                }
 
@@ -106,12 +210,23 @@ class WP_Upgrader {
                return true;
        } //end fs_connect();
 
-       function download_package($package) {
+       /**
+        * Download a package.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @param string $package The URI of the package. If this is the full path to an
+        *                        existing local file, it will be returned untouched.
+        * @return string|WP_Error The full path to the downloaded package file, or a {@see WP_Error} object.
+        */
+       public function download_package( $package ) {
 
                /**
                 * Filter whether to return the package.
                 *
                 * @since 3.7.0
+                * @access public
                 *
                 * @param bool        $reply   Whether to bail without returning the package.
                 *                             Default false.
@@ -138,7 +253,20 @@ class WP_Upgrader {
                return $download_file;
        }
 
-       function unpack_package($package, $delete_package = true) {
+       /**
+        * Unpack a compressed package file.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param string $package        Full path to the package file.
+        * @param bool   $delete_package Optional. Whether to delete the package file after attempting
+        *                               to unpack it. Default true.
+        * @return string|WP_Error The path to the unpacked contents, or a {@see WP_Error} on failure.
+        */
+       public function unpack_package( $package, $delete_package = true ) {
                global $wp_filesystem;
 
                $this->skin->feedback('unpack_package');
@@ -152,8 +280,8 @@ class WP_Upgrader {
                                $wp_filesystem->delete($upgrade_folder . $file['name'], true);
                }
 
-               //We need a working directory
-               $working_dir = $upgrade_folder . basename($package, '.zip');
+               // We need a working directory - Strip off any .tmp or .zip suffixes
+               $working_dir = $upgrade_folder . basename( basename( $package, '.tmp' ), '.zip' );
 
                // Clean up working directory
                if ( $wp_filesystem->is_dir($working_dir) )
@@ -177,7 +305,98 @@ class WP_Upgrader {
                return $working_dir;
        }
 
-       function install_package( $args = array() ) {
+       /**
+        * Clears the directory where this item is going to be installed into.
+        *
+        * @since 4.3.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param string $remote_destination The location on the remote filesystem to be cleared
+        * @return bool|WP_Error True upon success, WP_Error on failure.
+        */
+       public function clear_destination( $remote_destination ) {
+               global $wp_filesystem;
+
+               if ( ! $wp_filesystem->exists( $remote_destination ) ) {
+                       return true;
+               }
+
+               // Check all files are writable before attempting to clear the destination.
+               $unwritable_files = array();
+
+               $_files = $wp_filesystem->dirlist( $remote_destination, true, true );
+
+               // Flatten the resulting array, iterate using each as we append to the array during iteration.
+               while ( $f = each( $_files ) ) {
+                       $file = $f['value'];
+                       $name = $f['key'];
+
+                       if ( ! isset( $file['files'] ) ) {
+                               continue;
+                       }
+
+                       foreach ( $file['files'] as $filename => $details ) {
+                               $_files[ $name . '/' . $filename ] = $details;
+                       }
+               }
+
+               // Check writability.
+               foreach ( $_files as $filename => $file_details ) {
+                       if ( ! $wp_filesystem->is_writable( $remote_destination . $filename ) ) {
+
+                               // Attempt to alter permissions to allow writes and try again.
+                               $wp_filesystem->chmod( $remote_destination . $filename, ( 'd' == $file_details['type'] ? FS_CHMOD_DIR : FS_CHMOD_FILE ) );
+                               if ( ! $wp_filesystem->is_writable( $remote_destination . $filename ) ) {
+                                       $unwritable_files[] = $filename;
+                               }
+                       }
+               }
+
+               if ( ! empty( $unwritable_files ) ) {
+                       return new WP_Error( 'files_not_writable', $this->strings['files_not_writable'], implode( ', ', $unwritable_files ) );
+               }
+
+               if ( ! $wp_filesystem->delete( $remote_destination, true ) ) {
+                       return new WP_Error( 'remove_old_failed', $this->strings['remove_old_failed'] );
+               }
+
+               return true;
+       }
+
+       /**
+        * Install a package.
+        *
+        * Copies the contents of a package form a source directory, and installs them in
+        * a destination directory. Optionally removes the source. It can also optionally
+        * clear out the destination folder if it already exists.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        * @global array              $wp_theme_directories
+        *
+        * @param array|string $args {
+        *     Optional. Array or string of arguments for installing a package. Default empty array.
+        *
+        *     @type string $source                      Required path to the package source. Default empty.
+        *     @type string $destination                 Required path to a folder to install the package in.
+        *                                               Default empty.
+        *     @type bool   $clear_destination           Whether to delete any files already in the destination
+        *                                               folder. Default false.
+        *     @type bool   $clear_working               Whether to delete the files form the working directory
+        *                                               after copying to the destination. Default false.
+        *     @type bool   $abort_if_destination_exists Whether to abort the installation if
+        *                                               the destination folder already exists. Default true.
+        *     @type array  $hook_extra                  Extra arguments to pass to the filter hooks called by
+        *                                               {@see WP_Upgrader::install_package()}. Default empty array.
+        * }
+        *
+        * @return array|WP_Error The result (also stored in `WP_Upgrader:$result`), or a {@see WP_Error} on failure.
+        */
+       public function install_package( $args = array() ) {
                global $wp_filesystem, $wp_theme_directories;
 
                $defaults = array(
@@ -190,14 +409,18 @@ class WP_Upgrader {
                );
 
                $args = wp_parse_args($args, $defaults);
-               extract($args);
 
-               @set_time_limit( 300 );
+               // These were previously extract()'d.
+               $source = $args['source'];
+               $destination = $args['destination'];
+               $clear_destination = $args['clear_destination'];
 
-               if ( empty($source) || empty($destination) )
-                       return new WP_Error('bad_request', $this->strings['bad_request']);
+               @set_time_limit( 300 );
 
-               $this->skin->feedback('installing_package');
+               if ( empty( $source ) || empty( $destination ) ) {
+                       return new WP_Error( 'bad_request', $this->strings['bad_request'] );
+               }
+               $this->skin->feedback( 'installing_package' );
 
                /**
                 * Filter the install response before the installation has started.
@@ -211,77 +434,90 @@ class WP_Upgrader {
                 * @param bool|WP_Error $response   Response.
                 * @param array         $hook_extra Extra arguments passed to hooked filters.
                 */
-               $res = apply_filters( 'upgrader_pre_install', true, $hook_extra );
-               if ( is_wp_error($res) )
+               $res = apply_filters( 'upgrader_pre_install', true, $args['hook_extra'] );
+
+               if ( is_wp_error( $res ) ) {
                        return $res;
+               }
 
                //Retain the Original source and destinations
-               $remote_source = $source;
+               $remote_source = $args['source'];
                $local_destination = $destination;
 
-               $source_files = array_keys( $wp_filesystem->dirlist($remote_source) );
-               $remote_destination = $wp_filesystem->find_folder($local_destination);
+               $source_files = array_keys( $wp_filesystem->dirlist( $remote_source ) );
+               $remote_destination = $wp_filesystem->find_folder( $local_destination );
 
                //Locate which directory to copy to the new folder, This is based on the actual folder holding the files.
-               if ( 1 == count($source_files) && $wp_filesystem->is_dir( trailingslashit($source) . $source_files[0] . '/') ) //Only one folder? Then we want its contents.
-                       $source = trailingslashit($source) . trailingslashit($source_files[0]);
-               elseif ( count($source_files) == 0 )
+               if ( 1 == count( $source_files ) && $wp_filesystem->is_dir( trailingslashit( $args['source'] ) . $source_files[0] . '/' ) ) { //Only one folder? Then we want its contents.
+                       $source = trailingslashit( $args['source'] ) . trailingslashit( $source_files[0] );
+               } elseif ( count( $source_files ) == 0 ) {
                        return new WP_Error( 'incompatible_archive_empty', $this->strings['incompatible_archive'], $this->strings['no_files'] ); // There are no files?
-               else //It's only a single file, the upgrader will use the foldername of this file as the destination folder. foldername is based on zip filename.
-                       $source = trailingslashit($source);
+               } else { // It's only a single file, the upgrader will use the folder name of this file as the destination folder. Folder name is based on zip filename.
+                       $source = trailingslashit( $args['source'] );
+               }
 
                /**
                 * Filter the source file location for the upgrade package.
                 *
                 * @since 2.8.0
+                * @since 4.4.0 The $hook_extra parameter became available.
                 *
                 * @param string      $source        File source location.
-                * @param string      $remote_source Remove file source location.
+                * @param string      $remote_source Remote file source location.
                 * @param WP_Upgrader $this          WP_Upgrader instance.
+                * @param array       $hook_extra    Extra arguments passed to hooked filters.
                 */
-               $source = apply_filters( 'upgrader_source_selection', $source, $remote_source, $this );
-               if ( is_wp_error($source) )
+               $source = apply_filters( 'upgrader_source_selection', $source, $remote_source, $this, $args['hook_extra'] );
+
+               if ( is_wp_error( $source ) ) {
                        return $source;
+               }
 
-               //Has the source location changed? If so, we need a new source_files list.
-               if ( $source !== $remote_source )
-                       $source_files = array_keys( $wp_filesystem->dirlist($source) );
+               // Has the source location changed? If so, we need a new source_files list.
+               if ( $source !== $remote_source ) {
+                       $source_files = array_keys( $wp_filesystem->dirlist( $source ) );
+               }
 
-               // Protection against deleting files in any important base directories.
-               // Theme_Upgrader & Plugin_Upgrader also trigger this, as they pass the destination directory (WP_PLUGIN_DIR / wp-content/themes)
-               // intending to copy the directory into the directory, whilst they pass the source as the actual files to copy.
+               /*
+                * Protection against deleting files in any important base directories.
+                * Theme_Upgrader & Plugin_Upgrader also trigger this, as they pass the
+                * destination directory (WP_PLUGIN_DIR / wp-content/themes) intending
+                * to copy the directory into the directory, whilst they pass the source
+                * as the actual files to copy.
+                */
                $protected_directories = array( ABSPATH, WP_CONTENT_DIR, WP_PLUGIN_DIR, WP_CONTENT_DIR . '/themes' );
-               if ( is_array( $wp_theme_directories ) )
+
+               if ( is_array( $wp_theme_directories ) ) {
                        $protected_directories = array_merge( $protected_directories, $wp_theme_directories );
+               }
+
                if ( in_array( $destination, $protected_directories ) ) {
-                       $remote_destination = trailingslashit($remote_destination) . trailingslashit(basename($source));
-                       $destination = trailingslashit($destination) . trailingslashit(basename($source));
+                       $remote_destination = trailingslashit( $remote_destination ) . trailingslashit( basename( $source ) );
+                       $destination = trailingslashit( $destination ) . trailingslashit( basename( $source ) );
                }
 
                if ( $clear_destination ) {
-                       //We're going to clear the destination if there's something there
+                       // We're going to clear the destination if there's something there.
                        $this->skin->feedback('remove_old');
-                       $removed = true;
-                       if ( $wp_filesystem->exists($remote_destination) )
-                               $removed = $wp_filesystem->delete($remote_destination, true);
+
+                       $removed = $this->clear_destination( $remote_destination );
 
                        /**
                         * Filter whether the upgrader cleared the destination.
                         *
                         * @since 2.8.0
                         *
-                        * @param bool   $removed            Whether the destination was cleared.
+                        * @param mixed  $removed            Whether the destination was cleared. true on success, WP_Error on failure
                         * @param string $local_destination  The local package destination.
                         * @param string $remote_destination The remote package destination.
                         * @param array  $hook_extra         Extra arguments passed to hooked filters.
                         */
-                       $removed = apply_filters( 'upgrader_clear_destination', $removed, $local_destination, $remote_destination, $hook_extra );
+                       $removed = apply_filters( 'upgrader_clear_destination', $removed, $local_destination, $remote_destination, $args['hook_extra'] );
 
-                       if ( is_wp_error($removed) )
+                       if ( is_wp_error( $removed ) ) {
                                return $removed;
-                       else if ( ! $removed )
-                               return new WP_Error('remove_old_failed', $this->strings['remove_old_failed']);
-               } elseif ( $abort_if_destination_exists && $wp_filesystem->exists($remote_destination) ) {
+                       }
+               } elseif ( $args['abort_if_destination_exists'] && $wp_filesystem->exists($remote_destination) ) {
                        //If we're not clearing the destination folder and something exists there already, Bail.
                        //But first check to see if there are actually any files in the folder.
                        $_files = $wp_filesystem->dirlist($remote_destination);
@@ -292,27 +528,31 @@ class WP_Upgrader {
                }
 
                //Create destination if needed
-               if ( !$wp_filesystem->exists($remote_destination) )
-                       if ( !$wp_filesystem->mkdir($remote_destination, FS_CHMOD_DIR) )
+               if ( ! $wp_filesystem->exists( $remote_destination ) ) {
+                       if ( ! $wp_filesystem->mkdir( $remote_destination, FS_CHMOD_DIR ) ) {
                                return new WP_Error( 'mkdir_failed_destination', $this->strings['mkdir_failed'], $remote_destination );
-
+                       }
+               }
                // Copy new version of item into place.
                $result = copy_dir($source, $remote_destination);
                if ( is_wp_error($result) ) {
-                       if ( $clear_working )
-                               $wp_filesystem->delete($remote_source, true);
+                       if ( $args['clear_working'] ) {
+                               $wp_filesystem->delete( $remote_source, true );
+                       }
                        return $result;
                }
 
                //Clear the Working folder?
-               if ( $clear_working )
-                       $wp_filesystem->delete($remote_source, true);
+               if ( $args['clear_working'] ) {
+                       $wp_filesystem->delete( $remote_source, true );
+               }
 
                $destination_name = basename( str_replace($local_destination, '', $destination) );
-               if ( '.' == $destination_name )
+               if ( '.' == $destination_name ) {
                        $destination_name = '';
+               }
 
-               $this->result = compact('local_source', 'source', 'source_name', 'source_files', 'destination', 'destination_name', 'local_destination', 'remote_destination', 'clear_destination', 'delete_source_dir');
+               $this->result = compact( 'source', 'source_files', 'destination', 'destination_name', 'local_destination', 'remote_destination', 'clear_destination' );
 
                /**
                 * Filter the install response after the installation has finished.
@@ -323,7 +563,7 @@ class WP_Upgrader {
                 * @param array $hook_extra Extra arguments passed to hooked filters.
                 * @param array $result     Installation result data.
                 */
-               $res = apply_filters( 'upgrader_post_install', true, $hook_extra, $this->result );
+               $res = apply_filters( 'upgrader_post_install', true, $args['hook_extra'], $this->result );
 
                if ( is_wp_error($res) ) {
                        $this->result = $res;
@@ -334,7 +574,41 @@ class WP_Upgrader {
                return $this->result;
        }
 
-       function run($options) {
+       /**
+        * Run an upgrade/install.
+        *
+        * Attempts to download the package (if it is not a local file), unpack it, and
+        * install it in the destination folder.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @param array $options {
+        *     Array or string of arguments for upgrading/installing a package.
+        *
+        *     @type string $package                     The full path or URI of the package to install.
+        *                                               Default empty.
+        *     @type string $destination                 The full path to the destination folder.
+        *                                               Default empty.
+        *     @type bool   $clear_destination           Whether to delete any files already in the
+        *                                               destination folder. Default false.
+        *     @type bool   $clear_working               Whether to delete the files form the working
+        *                                               directory after copying to the destination.
+        *                                               Default false.
+        *     @type bool   $abort_if_destination_exists Whether to abort the installation if the destination
+        *                                               folder already exists. When true, `$clear_destination`
+        *                                               should be false. Default true.
+        *     @type bool   $is_multi                    Whether this run is one of multiple upgrade/install
+        *                                               actions being performed in bulk. When true, the skin
+        *                                               {@see WP_Upgrader::header()} and {@see WP_Upgrader::footer()}
+        *                                               aren't called. Default false.
+        *     @type array  $hook_extra                  Extra arguments to pass to the filter hooks called by
+        *                                               {@see WP_Upgrader::run()}.
+        * }
+        * @return array|false|WP_error The result from self::install_package() on success, otherwise a WP_Error,
+        *                              or false if unable to connect to the filesystem.
+        */
+       public function run( $options ) {
 
                $defaults = array(
                        'package' => '', // Please always pass this.
@@ -346,18 +620,38 @@ class WP_Upgrader {
                        'hook_extra' => array() // Pass any extra $hook_extra args here, this will be passed to any hooked filters.
                );
 
-               $options = wp_parse_args($options, $defaults);
-               extract($options);
+               $options = wp_parse_args( $options, $defaults );
+
+               /**
+                * Filter the package options before running an update.
+                *
+                * @since 4.3.0
+                *
+                * @param array $options {
+                *     Options used by the upgrader.
+                *
+                *     @type string $package                     Package for update.
+                *     @type string $destination                 Update location.
+                *     @type bool   $clear_destination           Clear the destination resource.
+                *     @type bool   $clear_working               Clear the working resource.
+                *     @type bool   $abort_if_destination_exists Abort if the Destination directory exists.
+                *     @type bool   $is_multi                    Whether the upgrader is running multiple times.
+                *     @type array  $hook_extra                  Extra hook arguments.
+                * }
+                */
+               $options = apply_filters( 'upgrader_package_options', $options );
 
-               if ( ! $is_multi ) // call $this->header separately if running multiple times
+               if ( ! $options['is_multi'] ) { // call $this->header separately if running multiple times
                        $this->skin->header();
+               }
 
                // Connect to the Filesystem first.
-               $res = $this->fs_connect( array(WP_CONTENT_DIR, $destination) );
+               $res = $this->fs_connect( array( WP_CONTENT_DIR, $options['destination'] ) );
                // Mainly for non-connected filesystem.
                if ( ! $res ) {
-                       if ( ! $is_multi )
+                       if ( ! $options['is_multi'] ) {
                                $this->skin->footer();
+                       }
                        return false;
                }
 
@@ -366,41 +660,47 @@ class WP_Upgrader {
                if ( is_wp_error($res) ) {
                        $this->skin->error($res);
                        $this->skin->after();
-                       if ( ! $is_multi )
+                       if ( ! $options['is_multi'] ) {
                                $this->skin->footer();
+                       }
                        return $res;
                }
 
-               //Download the package (Note, This just returns the filename of the file if the package is a local file)
-               $download = $this->download_package( $package );
+               /*
+                * Download the package (Note, This just returns the filename
+                * of the file if the package is a local file)
+                */
+               $download = $this->download_package( $options['package'] );
                if ( is_wp_error($download) ) {
                        $this->skin->error($download);
                        $this->skin->after();
-                       if ( ! $is_multi )
+                       if ( ! $options['is_multi'] ) {
                                $this->skin->footer();
+                       }
                        return $download;
                }
 
-               $delete_package = ($download != $package); // Do not delete a "local" file
+               $delete_package = ( $download != $options['package'] ); // Do not delete a "local" file
 
-               //Unzips the file into a temporary directory
+               // Unzips the file into a temporary directory.
                $working_dir = $this->unpack_package( $download, $delete_package );
                if ( is_wp_error($working_dir) ) {
                        $this->skin->error($working_dir);
                        $this->skin->after();
-                       if ( ! $is_multi )
+                       if ( ! $options['is_multi'] ) {
                                $this->skin->footer();
+                       }
                        return $working_dir;
                }
 
-               //With the given options, this installs it to the destination directory.
+               // With the given options, this installs it to the destination directory.
                $result = $this->install_package( array(
                        'source' => $working_dir,
-                       'destination' => $destination,
-                       'clear_destination' => $clear_destination,
-                       'abort_if_destination_exists' => $abort_if_destination_exists,
-                       'clear_working' => $clear_working,
-                       'hook_extra' => $hook_extra
+                       'destination' => $options['destination'],
+                       'clear_destination' => $options['clear_destination'],
+                       'abort_if_destination_exists' => $options['abort_if_destination_exists'],
+                       'clear_working' => $options['clear_working'],
+                       'hook_extra' => $options['hook_extra']
                ) );
 
                $this->skin->set_result($result);
@@ -408,23 +708,35 @@ class WP_Upgrader {
                        $this->skin->error($result);
                        $this->skin->feedback('process_failed');
                } else {
-                       //Install Succeeded
+                       // Install succeeded.
                        $this->skin->feedback('process_success');
                }
 
                $this->skin->after();
 
-               if ( ! $is_multi ) {
+               if ( ! $options['is_multi'] ) {
 
                        /** This action is documented in wp-admin/includes/class-wp-upgrader.php */
-                       do_action( 'upgrader_process_complete', $this, $hook_extra );
+                       do_action( 'upgrader_process_complete', $this, $options['hook_extra'] );
                        $this->skin->footer();
                }
 
                return $result;
        }
 
-       function maintenance_mode($enable = false) {
+       /**
+        * Toggle maintenance mode for the site.
+        *
+        * Creates/deletes the maintenance file to enable/disable maintenance mode.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param bool $enable True to enable maintenance mode, false to disable.
+        */
+       public function maintenance_mode( $enable = false ) {
                global $wp_filesystem;
                $file = $wp_filesystem->abspath() . '.maintenance';
                if ( $enable ) {
@@ -433,7 +745,7 @@ class WP_Upgrader {
                        $maintenance_string = '<?php $upgrading = ' . time() . '; ?>';
                        $wp_filesystem->delete($file);
                        $wp_filesystem->put_contents($file, $maintenance_string, FS_CHMOD_FILE);
-               } else if ( !$enable && $wp_filesystem->exists($file) ) {
+               } elseif ( ! $enable && $wp_filesystem->exists( $file ) ) {
                        $this->skin->feedback('maintenance_end');
                        $wp_filesystem->delete($file);
                }
@@ -442,18 +754,44 @@ class WP_Upgrader {
 }
 
 /**
- * Plugin Upgrader class for WordPress Plugins, It is designed to upgrade/install plugins from a local zip, remote zip URL, or uploaded zip file.
+ * Core class used for upgrading/installing plugins.
+ *
+ * It is designed to upgrade/install plugins from a local zip, remote zip URL,
+ * or uploaded zip file.
  *
- * @package WordPress
- * @subpackage Upgrader
  * @since 2.8.0
+ *
+ * @see WP_Upgrader
  */
 class Plugin_Upgrader extends WP_Upgrader {
 
-       var $result;
-       var $bulk = false;
+       /**
+        * Plugin upgrade result.
+        *
+        * @since 2.8.0
+        * @access public
+        * @var array|WP_Error $result
+        *
+        * @see WP_Upgrader::$result
+        */
+       public $result;
 
-       function upgrade_strings() {
+       /**
+        * Whether a bulk upgrade/install is being performed.
+        *
+        * @since 2.9.0
+        * @access public
+        * @var bool $bulk
+        */
+       public $bulk = false;
+
+       /**
+        * Initialize the upgrade strings.
+        *
+        * @since 2.8.0
+        * @access public
+        */
+       public function upgrade_strings() {
                $this->strings['up_to_date'] = __('The plugin is at the latest version.');
                $this->strings['no_package'] = __('Update package not available.');
                $this->strings['downloading_package'] = __('Downloading update from <span class="code">%s</span>&#8230;');
@@ -462,9 +800,16 @@ class Plugin_Upgrader extends WP_Upgrader {
                $this->strings['remove_old_failed'] = __('Could not remove the old plugin.');
                $this->strings['process_failed'] = __('Plugin update failed.');
                $this->strings['process_success'] = __('Plugin updated successfully.');
+               $this->strings['process_bulk_success'] = __('Plugins updated successfully.');
        }
 
-       function install_strings() {
+       /**
+        * Initialize the install strings.
+        *
+        * @since 2.8.0
+        * @access public
+        */
+       public function install_strings() {
                $this->strings['no_package'] = __('Install package not available.');
                $this->strings['downloading_package'] = __('Downloading install package from <span class="code">%s</span>&#8230;');
                $this->strings['unpack_package'] = __('Unpacking the package&#8230;');
@@ -474,7 +819,23 @@ class Plugin_Upgrader extends WP_Upgrader {
                $this->strings['process_success'] = __('Plugin installed successfully.');
        }
 
-       function install( $package, $args = array() ) {
+       /**
+        * Install a plugin package.
+        *
+        * @since 2.8.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the plugin update cache optional.
+        * @access public
+        *
+        * @param string $package The full local path or URI of the package.
+        * @param array  $args {
+        *     Optional. Other arguments for installing a plugin package. Default empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the plugin updates cache if successful.
+        *                                    Default true.
+        * }
+        * @return bool|WP_Error True if the install was successful, false or a WP_Error otherwise.
+        */
+       public function install( $package, $args = array() ) {
 
                $defaults = array(
                        'clear_update_cache' => true,
@@ -485,6 +846,8 @@ class Plugin_Upgrader extends WP_Upgrader {
                $this->install_strings();
 
                add_filter('upgrader_source_selection', array($this, 'check_package') );
+               // Clear cache so wp_update_plugins() knows about the new plugin.
+               add_action( 'upgrader_process_complete', 'wp_clean_plugins_cache', 9, 0 );
 
                $this->run( array(
                        'package' => $package,
@@ -497,6 +860,7 @@ class Plugin_Upgrader extends WP_Upgrader {
                        )
                ) );
 
+               remove_action( 'upgrader_process_complete', 'wp_clean_plugins_cache', 9 );
                remove_filter('upgrader_source_selection', array($this, 'check_package') );
 
                if ( ! $this->result || is_wp_error($this->result) )
@@ -508,7 +872,23 @@ class Plugin_Upgrader extends WP_Upgrader {
                return true;
        }
 
-       function upgrade( $plugin, $args = array() ) {
+       /**
+        * Upgrade a plugin.
+        *
+        * @since 2.8.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the plugin update cache optional.
+        * @access public
+        *
+        * @param string $plugin The basename path to the main plugin file.
+        * @param array  $args {
+        *     Optional. Other arguments for upgrading a plugin package. Default empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the plugin updates cache if successful.
+        *                                    Default true.
+        * }
+        * @return bool|WP_Error True if the upgrade was successful, false or a {@see WP_Error} object otherwise.
+        */
+       public function upgrade( $plugin, $args = array() ) {
 
                $defaults = array(
                        'clear_update_cache' => true,
@@ -559,7 +939,23 @@ class Plugin_Upgrader extends WP_Upgrader {
                return true;
        }
 
-       function bulk_upgrade( $plugins, $args = array() ) {
+       /**
+        * Bulk upgrade several plugins at once.
+        *
+        * @since 2.8.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the plugin update cache optional.
+        * @access public
+        *
+        * @param array $plugins Array of the basename paths of the plugins' main files.
+        * @param array $args {
+        *     Optional. Other arguments for upgrading several plugins at once. Default empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the plugin updates cache if successful.
+        *                                    Default true.
+        * }
+        * @return array|false An array of results indexed by plugin file, or false if unable to connect to the filesystem.
+        */
+       public function bulk_upgrade( $plugins, $args = array() ) {
 
                $defaults = array(
                        'clear_update_cache' => true,
@@ -585,10 +981,12 @@ class Plugin_Upgrader extends WP_Upgrader {
 
                $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.
+               /*
+                * 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] ) );
@@ -612,7 +1010,7 @@ class Plugin_Upgrader extends WP_Upgrader {
                                continue;
                        }
 
-                       // Get the URL to the zip file
+                       // Get the URL to the zip file.
                        $r = $current->response[ $plugin ];
 
                        $this->skin->plugin_active = is_plugin_active($plugin);
@@ -667,29 +1065,47 @@ class Plugin_Upgrader extends WP_Upgrader {
                // Cleanup our hooks, in case something else does a upgrade on this connection.
                remove_filter('upgrader_clear_destination', array($this, 'delete_old_plugin'));
 
-               // Force refresh of plugin update information
+               // Force refresh of plugin update information.
                wp_clean_plugins_cache( $parsed_args['clear_update_cache'] );
 
                return $results;
        }
 
-       function check_package($source) {
+       /**
+        * Check a source package to be sure it contains a plugin.
+        *
+        * This function is added to the {@see 'upgrader_source_selection'} filter by
+        * {@see Plugin_Upgrader::install()}.
+        *
+        * @since 3.3.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param string $source The path to the downloaded package source.
+        * @return string|WP_Error The source as passed, or a {@see WP_Error} object
+        *                         if no plugins were found.
+        */
+       public function check_package($source) {
                global $wp_filesystem;
 
                if ( is_wp_error($source) )
                        return $source;
 
                $working_directory = str_replace( $wp_filesystem->wp_content_dir(), trailingslashit(WP_CONTENT_DIR), $source);
-               if ( ! is_dir($working_directory) ) // Sanity check, if the above fails, lets not prevent installation.
+               if ( ! is_dir($working_directory) ) // Sanity check, if the above fails, let's not prevent installation.
                        return $source;
 
                // Check the folder contains at least 1 valid plugin.
                $plugins_found = false;
-               foreach ( glob( $working_directory . '*.php' ) as $file ) {
-                       $info = get_plugin_data($file, false, false);
-                       if ( !empty( $info['Name'] ) ) {
-                               $plugins_found = true;
-                               break;
+               $files = glob( $working_directory . '*.php' );
+               if ( $files ) {
+                       foreach ( $files as $file ) {
+                               $info = get_plugin_data( $file, false, false );
+                               if ( ! empty( $info['Name'] ) ) {
+                                       $plugins_found = true;
+                                       break;
+                               }
                        }
                }
 
@@ -699,8 +1115,17 @@ class Plugin_Upgrader extends WP_Upgrader {
                return $source;
        }
 
-       //return plugin info.
-       function plugin_info() {
+       /**
+        * Retrieve the path to the file that contains the plugin info.
+        *
+        * This isn't used internally in the class, but is called by the skins.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @return string|false The full path to the main plugin file, or false.
+        */
+       public function plugin_info() {
                if ( ! is_array($this->result) )
                        return false;
                if ( empty($this->result['destination_name']) )
@@ -715,8 +1140,20 @@ class Plugin_Upgrader extends WP_Upgrader {
                return $this->result['destination_name'] . '/' . $pluginfiles[0];
        }
 
-       //Hooked to pre_install
-       function deactivate_plugin_before_upgrade($return, $plugin) {
+       /**
+        * Deactivates a plugin before it is upgraded.
+        *
+        * Hooked to the {@see 'upgrader_pre_install'} filter by {@see Plugin_Upgrader::upgrade()}.
+        *
+        * @since 2.8.0
+        * @since 4.1.0 Added a return value.
+        * @access public
+        *
+        * @param bool|WP_Error  $return Upgrade offer return.
+        * @param array          $plugin Plugin package arguments.
+        * @return bool|WP_Error The passed in $return param or {@see WP_Error}.
+        */
+       public function deactivate_plugin_before_upgrade($return, $plugin) {
 
                if ( is_wp_error($return) ) //Bypass.
                        return $return;
@@ -733,10 +1170,28 @@ class Plugin_Upgrader extends WP_Upgrader {
                        //Deactivate the plugin silently, Prevent deactivation hooks from running.
                        deactivate_plugins($plugin, true);
                }
+
+               return $return;
        }
 
-       //Hooked to upgrade_clear_destination
-       function delete_old_plugin($removed, $local_destination, $remote_destination, $plugin) {
+       /**
+        * Delete the old plugin during an upgrade.
+        *
+        * Hooked to the {@see 'upgrader_clear_destination'} filter by
+        * {@see Plugin_Upgrader::upgrade()} and {@see Plugin_Upgrader::bulk_upgrade()}.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+     *
+        * @param bool|WP_Error $removed
+        * @param string        $local_destination
+        * @param string        $remote_destination
+        * @param array         $plugin
+        * @return WP_Error|bool
+        */
+       public function delete_old_plugin($removed, $local_destination, $remote_destination, $plugin) {
                global $wp_filesystem;
 
                if ( is_wp_error($removed) )
@@ -766,18 +1221,43 @@ class Plugin_Upgrader extends WP_Upgrader {
 }
 
 /**
- * Theme Upgrader class for WordPress Themes, It is designed to upgrade/install themes from a local zip, remote zip URL, or uploaded zip file.
+ * Core class used for upgrading/installing themes.
+ *
+ * It is designed to upgrade/install themes from a local zip, remote zip URL,
+ * or uploaded zip file.
  *
- * @package WordPress
- * @subpackage Upgrader
  * @since 2.8.0
+ *
+ * @see WP_Upgrader
  */
 class Theme_Upgrader extends WP_Upgrader {
 
-       var $result;
-       var $bulk = false;
+       /**
+        * Result of the theme upgrade offer.
+        *
+        * @since 2.8.0
+        * @access public
+        * @var array|WP_Error $result
+        * @see WP_Upgrader::$result
+        */
+       public $result;
 
-       function upgrade_strings() {
+       /**
+        * Whether multiple themes are being upgraded/installed in bulk.
+        *
+        * @since 2.9.0
+        * @access public
+        * @var bool $bulk
+        */
+       public $bulk = false;
+
+       /**
+        * Initialize the upgrade strings.
+        *
+        * @since 2.8.0
+        * @access public
+        */
+       public function upgrade_strings() {
                $this->strings['up_to_date'] = __('The theme is at the latest version.');
                $this->strings['no_package'] = __('Update package not available.');
                $this->strings['downloading_package'] = __('Downloading update from <span class="code">%s</span>&#8230;');
@@ -788,7 +1268,13 @@ class Theme_Upgrader extends WP_Upgrader {
                $this->strings['process_success'] = __('Theme updated successfully.');
        }
 
-       function install_strings() {
+       /**
+        * Initialize the install strings.
+        *
+        * @since 2.8.0
+        * @access public
+        */
+       public function install_strings() {
                $this->strings['no_package'] = __('Install package not available.');
                $this->strings['downloading_package'] = __('Downloading install package from <span class="code">%s</span>&#8230;');
                $this->strings['unpack_package'] = __('Unpacking the package&#8230;');
@@ -808,7 +1294,20 @@ class Theme_Upgrader extends WP_Upgrader {
                $this->strings['parent_theme_not_found'] = __('<strong>The parent theme could not be found.</strong> You will need to install the parent theme, <strong>%s</strong>, before you can use this child theme.');
        }
 
-       function check_parent_theme_filter($install_result, $hook_extra, $child_result) {
+       /**
+        * Check if a child theme is being installed and we need to install its parent.
+        *
+        * Hooked to the {@see 'upgrader_post_install'} filter by {@see Theme_Upgrader::install()}.
+        *
+        * @since 3.4.0
+        * @access public
+        *
+        * @param bool  $install_result
+        * @param array $hook_extra
+        * @param array $child_result
+        * @return type
+        */
+       public function check_parent_theme_filter( $install_result, $hook_extra, $child_result ) {
                // Check to see if we need to install a parent theme
                $theme_info = $this->theme_info();
 
@@ -823,7 +1322,7 @@ class Theme_Upgrader extends WP_Upgrader {
                        return $install_result;
                }
 
-               // We don't have the parent theme, lets install it
+               // We don't have the parent theme, let's install it.
                $api = themes_api('theme_information', array('slug' => $theme_info->get('Template'), 'fields' => array('sections' => false, 'tags' => false) ) ); //Save on a bit of bandwidth.
 
                if ( ! $api || is_wp_error($api) ) {
@@ -867,12 +1366,42 @@ class Theme_Upgrader extends WP_Upgrader {
                return $install_result;
        }
 
-       function hide_activate_preview_actions($actions) {
+       /**
+        * Don't display the activate and preview actions to the user.
+        *
+        * Hooked to the {@see 'install_theme_complete_actions'} filter by
+        * {@see Theme_Upgrader::check_parent_theme_filter()} when installing
+        * a child theme and installing the parent theme fails.
+        *
+        * @since 3.4.0
+        * @access public
+        *
+        * @param array $actions Preview actions.
+        * @return array
+        */
+       public function hide_activate_preview_actions( $actions ) {
                unset($actions['activate'], $actions['preview']);
                return $actions;
        }
 
-       function install( $package, $args = array() ) {
+       /**
+        * Install a theme package.
+        *
+        * @since 2.8.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the update cache optional.
+        * @access public
+        *
+        * @param string $package The full local path or URI of the package.
+        * @param array  $args {
+        *     Optional. Other arguments for installing a theme package. Default empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the updates cache if successful.
+        *                                    Default true.
+        * }
+        *
+        * @return bool|WP_Error True if the install was successful, false or a {@see WP_Error} object otherwise.
+        */
+       public function install( $package, $args = array() ) {
 
                $defaults = array(
                        'clear_update_cache' => true,
@@ -884,6 +1413,8 @@ class Theme_Upgrader extends WP_Upgrader {
 
                add_filter('upgrader_source_selection', array($this, 'check_package') );
                add_filter('upgrader_post_install', array($this, 'check_parent_theme_filter'), 10, 3);
+               // Clear cache so wp_update_themes() knows about the new theme.
+               add_action( 'upgrader_process_complete', 'wp_clean_themes_cache', 9, 0 );
 
                $this->run( array(
                        'package' => $package,
@@ -896,6 +1427,7 @@ class Theme_Upgrader extends WP_Upgrader {
                        ),
                ) );
 
+               remove_action( 'upgrader_process_complete', 'wp_clean_themes_cache', 9 );
                remove_filter('upgrader_source_selection', array($this, 'check_package') );
                remove_filter('upgrader_post_install', array($this, 'check_parent_theme_filter'));
 
@@ -908,7 +1440,23 @@ class Theme_Upgrader extends WP_Upgrader {
                return true;
        }
 
-       function upgrade( $theme, $args = array() ) {
+       /**
+        * Upgrade a theme.
+        *
+        * @since 2.8.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the update cache optional.
+        * @access public
+        *
+        * @param string $theme The theme slug.
+        * @param array  $args {
+        *     Optional. Other arguments for upgrading a theme. Default empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the update cache if successful.
+        *                                    Default true.
+        * }
+        * @return bool|WP_Error True if the upgrade was successful, false or a {@see WP_Error} object otherwise.
+        */
+       public function upgrade( $theme, $args = array() ) {
 
                $defaults = array(
                        'clear_update_cache' => true,
@@ -958,7 +1506,23 @@ class Theme_Upgrader extends WP_Upgrader {
                return true;
        }
 
-       function bulk_upgrade( $themes, $args = array() ) {
+       /**
+        * Upgrade several themes at once.
+        *
+        * @since 3.0.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the update cache optional.
+        * @access public
+        *
+        * @param array $themes The theme slugs.
+        * @param array $args {
+        *     Optional. Other arguments for upgrading several themes at once. Default empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the update cache if successful.
+        *                                    Default true.
+        * }
+        * @return array[]|false An array of results, or false if unable to connect to the filesystem.
+        */
+       public function bulk_upgrade( $themes, $args = array() ) {
 
                $defaults = array(
                        'clear_update_cache' => true,
@@ -1022,6 +1586,7 @@ class Theme_Upgrader extends WP_Upgrader {
                                'destination' => get_theme_root( $theme ),
                                'clear_destination' => true,
                                'clear_working' => true,
+                               'is_multi' => true,
                                'hook_extra' => array(
                                        'theme' => $theme
                                ),
@@ -1059,7 +1624,22 @@ class Theme_Upgrader extends WP_Upgrader {
                return $results;
        }
 
-       function check_package($source) {
+       /**
+        * Check that the package source contains a valid theme.
+        *
+        * Hooked to the {@see 'upgrader_source_selection'} filter by {@see Theme_Upgrader::install()}.
+        * It will return an error if the theme doesn't have style.css or index.php
+        * files.
+        *
+        * @since 3.3.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param string $source The full path to the package source.
+        * @return string|WP_Error The source or a WP_Error.
+        */
+       public function check_package( $source ) {
                global $wp_filesystem;
 
                if ( is_wp_error($source) )
@@ -1067,27 +1647,57 @@ class Theme_Upgrader extends WP_Upgrader {
 
                // Check the folder contains a valid theme
                $working_directory = str_replace( $wp_filesystem->wp_content_dir(), trailingslashit(WP_CONTENT_DIR), $source);
-               if ( ! is_dir($working_directory) ) // Sanity check, if the above fails, lets not prevent installation.
+               if ( ! is_dir($working_directory) ) // Sanity check, if the above fails, let's not prevent installation.
                        return $source;
 
                // A proper archive should have a style.css file in the single subdirectory
-               if ( ! file_exists( $working_directory . 'style.css' ) )
-                       return new WP_Error( 'incompatible_archive_theme_no_style', $this->strings['incompatible_archive'], __( 'The theme is missing the <code>style.css</code> stylesheet.' ) );
+               if ( ! file_exists( $working_directory . 'style.css' ) ) {
+                       return new WP_Error( 'incompatible_archive_theme_no_style', $this->strings['incompatible_archive'],
+                               /* translators: %s: style.css */
+                               sprintf( __( 'The theme is missing the %s stylesheet.' ),
+                                       '<code>style.css</code>'
+                               )
+                       );
+               }
 
                $info = get_file_data( $working_directory . 'style.css', array( 'Name' => 'Theme Name', 'Template' => 'Template' ) );
 
-               if ( empty( $info['Name'] ) )
-                       return new WP_Error( 'incompatible_archive_theme_no_name', $this->strings['incompatible_archive'], __( "The <code>style.css</code> stylesheet doesn't contain a valid theme header." ) );
+               if ( empty( $info['Name'] ) ) {
+                       return new WP_Error( 'incompatible_archive_theme_no_name', $this->strings['incompatible_archive'],
+                               /* translators: %s: style.css */
+                               sprintf( __( 'The %s stylesheet doesn&#8217;t contain a valid theme header.' ),
+                                       '<code>style.css</code>'
+                               )
+                       );
+               }
 
                // If it's not a child theme, it must have at least an index.php to be legit.
-               if ( empty( $info['Template'] ) && ! file_exists( $working_directory . 'index.php' ) )
-                       return new WP_Error( 'incompatible_archive_theme_no_index', $this->strings['incompatible_archive'], __( 'The theme is missing the <code>index.php</code> file.' ) );
+               if ( empty( $info['Template'] ) && ! file_exists( $working_directory . 'index.php' ) ) {
+                       return new WP_Error( 'incompatible_archive_theme_no_index', $this->strings['incompatible_archive'],
+                               /* translators: %s: index.php */
+                               sprintf( __( 'The theme is missing the %s file.' ),
+                                       '<code>index.php</code>'
+                               )
+                       );
+               }
 
                return $source;
        }
 
-       function current_before($return, $theme) {
-
+       /**
+        * Turn on maintenance mode before attempting to upgrade the current theme.
+        *
+        * Hooked to the {@see 'upgrader_pre_install'} filter by {@see Theme_Upgrader::upgrade()} and
+        * {@see Theme_Upgrader::bulk_upgrade()}.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @param bool|WP_Error  $return
+        * @param array          $theme
+        * @return bool|WP_Error
+        */
+       public function current_before($return, $theme) {
                if ( is_wp_error($return) )
                        return $return;
 
@@ -1102,7 +1712,20 @@ class Theme_Upgrader extends WP_Upgrader {
                return $return;
        }
 
-       function current_after($return, $theme) {
+       /**
+        * Turn off maintenance mode after upgrading the current theme.
+        *
+        * Hooked to the {@see 'upgrader_post_install'} filter by {@see Theme_Upgrader::upgrade()}
+        * and {@see Theme_Upgrader::bulk_upgrade()}.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @param bool|WP_Error  $return
+        * @param array          $theme
+        * @return bool|WP_Error
+        */
+       public function current_after($return, $theme) {
                if ( is_wp_error($return) )
                        return $return;
 
@@ -1124,7 +1747,24 @@ class Theme_Upgrader extends WP_Upgrader {
                return $return;
        }
 
-       function delete_old_theme( $removed, $local_destination, $remote_destination, $theme ) {
+       /**
+        * Delete the old theme during an upgrade.
+        *
+        * Hooked to the {@see 'upgrader_clear_destination'} filter by {@see Theme_Upgrader::upgrade()}
+        * and {@see Theme_Upgrader::bulk_upgrade()}.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param bool   $removed
+        * @param string $local_destination
+        * @param string $remote_destination
+        * @param array  $theme
+        * @return bool
+        */
+       public function delete_old_theme( $removed, $local_destination, $remote_destination, $theme ) {
                global $wp_filesystem;
 
                if ( is_wp_error( $removed ) )
@@ -1143,7 +1783,19 @@ class Theme_Upgrader extends WP_Upgrader {
                return true;
        }
 
-       function theme_info($theme = null) {
+       /**
+        * Get the WP_Theme object for a theme.
+        *
+        * @since 2.8.0
+        * @since 3.0.0 The `$theme` argument was added.
+        * @access public
+        *
+        * @param string $theme The directory name of the theme. This is optional, and if not supplied,
+        *                      the directory name from the last result will be used.
+        * @return WP_Theme|false The theme's info object, or false `$theme` is not supplied
+        *                        and the last result isn't set.
+        */
+       public function theme_info($theme = null) {
 
                if ( empty($theme) ) {
                        if ( !empty($this->result['destination_name']) )
@@ -1156,39 +1808,111 @@ class Theme_Upgrader extends WP_Upgrader {
 
 }
 
-add_action( 'upgrader_process_complete', array( 'Language_Pack_Upgrader', 'async_upgrade' ), 20 );
-
 /**
- * Language pack upgrader, for updating translations of plugins, themes, and core.
+ * Core class used for updating/installing language packs (translations)
+ * for plugins, themes, and core.
  *
- * @package WordPress
- * @subpackage Upgrader
  * @since 3.7.0
+ *
+ * @see WP_Upgrader
  */
 class Language_Pack_Upgrader extends WP_Upgrader {
 
-       var $result;
-       var $bulk = true;
+       /**
+        * Result of the language pack upgrade.
+        *
+        * @since 3.7.0
+        * @access public
+        * @var array|WP_Error $result
+        * @see WP_Upgrader::$result
+        */
+       public $result;
+
+       /**
+        * Whether a bulk upgrade/install is being performed.
+        *
+        * @since 3.7.0
+        * @access public
+        * @var bool $bulk
+        */
+       public $bulk = true;
 
-       static function async_upgrade( $upgrader = false ) {
+       /**
+        * Asynchronously upgrades language packs after other upgrades have been made.
+        *
+        * Hooked to the {@see 'upgrader_process_complete'} action by default.
+        *
+        * @since 3.7.0
+        * @access public
+        * @static
+        *
+        * @param false|WP_Upgrader $upgrader Optional. WP_Upgrader instance or false. If `$upgrader` is
+        *                                    a Language_Pack_Upgrader instance, the method will bail to
+        *                                    avoid recursion. Otherwise unused. Default false.
+        */
+       public static function async_upgrade( $upgrader = false ) {
                // Avoid recursion.
-               if ( $upgrader && $upgrader instanceof Language_Pack_Upgrader )
+               if ( $upgrader && $upgrader instanceof Language_Pack_Upgrader ) {
                        return;
+               }
 
                // Nothing to do?
                $language_updates = wp_get_translation_updates();
-               if ( ! $language_updates )
+               if ( ! $language_updates ) {
                        return;
+               }
 
-               $skin = new Language_Pack_Upgrader_Skin( array(
-                       'skip_header_footer' => true,
-               ) );
+               /*
+                * Avoid messing with VCS installs, at least for now.
+                * Noted: this is not the ideal way to accomplish this.
+                */
+               $check_vcs = new WP_Automatic_Updater;
+               if ( $check_vcs->is_vcs_checkout( WP_CONTENT_DIR ) ) {
+                       return;
+               }
+
+               foreach ( $language_updates as $key => $language_update ) {
+                       $update = ! empty( $language_update->autoupdate );
+
+                       /**
+                        * Filter whether to asynchronously update translation for core, a plugin, or a theme.
+                        *
+                        * @since 4.0.0
+                        *
+                        * @param bool   $update          Whether to update.
+                        * @param object $language_update The update offer.
+                        */
+                       $update = apply_filters( 'async_update_translation', $update, $language_update );
+
+                       if ( ! $update ) {
+                               unset( $language_updates[ $key ] );
+                       }
+               }
+
+               if ( empty( $language_updates ) ) {
+                       return;
+               }
+
+               // Re-use the automatic upgrader skin if the parent upgrader is using it.
+               if ( $upgrader && $upgrader->skin instanceof Automatic_Upgrader_Skin ) {
+                       $skin = $upgrader->skin;
+               } else {
+                       $skin = new Language_Pack_Upgrader_Skin( array(
+                               'skip_header_footer' => true,
+                       ) );
+               }
 
                $lp_upgrader = new Language_Pack_Upgrader( $skin );
-               $lp_upgrader->upgrade();
+               $lp_upgrader->bulk_upgrade( $language_updates );
        }
 
-       function upgrade_strings() {
+       /**
+        * Initialize the upgrade strings.
+        *
+        * @since 3.7.0
+        * @access public
+        */
+       public function upgrade_strings() {
                $this->strings['starting_upgrade'] = __( 'Some of your translations need updating. Sit tight for a few more seconds while we update them as well.' );
                $this->strings['up_to_date'] = __( 'The translation is up to date.' ); // We need to silently skip this case
                $this->strings['no_package'] = __( 'Update package not available.' );
@@ -1198,14 +1922,50 @@ class Language_Pack_Upgrader extends WP_Upgrader {
                $this->strings['process_success'] = __( 'Translation updated successfully.' );
        }
 
-       function upgrade( $update = false, $args = array() ) {
-               if ( $update )
+       /**
+        * Upgrade a language pack.
+        *
+        * @since 3.7.0
+        * @access public
+        *
+        * @param string|false $update Optional. Whether an update offer is available. Default false.
+        * @param array        $args   Optional. Other optional arguments, see
+        *                             {@see Language_Pack_Upgrader::bulk_upgrade()}. Default empty array.
+        * @return array|bool|WP_Error The result of the upgrade, or a {@see wP_Error} object instead.
+        */
+       public function upgrade( $update = false, $args = array() ) {
+               if ( $update ) {
                        $update = array( $update );
+               }
+
                $results = $this->bulk_upgrade( $update, $args );
+
+               if ( ! is_array( $results ) ) {
+                       return $results;
+               }
+
                return $results[0];
        }
 
-       function bulk_upgrade( $language_updates = array(), $args = array() ) {
+       /**
+        * Bulk upgrade language packs.
+        *
+        * @since 3.7.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param array $language_updates Optional. Language pack updates. Default empty array.
+        * @param array $args {
+        *     Optional. Other arguments for upgrading multiple language packs. Default empty array
+        *
+        *     @type bool $clear_update_cache Whether to clear the update cache when done.
+        *                                    Default true.
+        * }
+        * @return array|bool|WP_Error Will return an array of results, or true if there are no updates,
+        *                                   false or WP_Error for initial errors.
+        */
+       public function bulk_upgrade( $language_updates = array(), $args = array() ) {
                global $wp_filesystem;
 
                $defaults = array(
@@ -1233,7 +1993,13 @@ class Language_Pack_Upgrader extends WP_Upgrader {
                if ( 'upgrader_process_complete' == current_filter() )
                        $this->skin->feedback( 'starting_upgrade' );
 
-               add_filter( 'upgrader_source_selection', array( &$this, 'check_package' ), 10, 3 );
+               // Remove any existing upgrade filters from the plugin/theme upgraders #WP29425 & #WP29230
+               remove_all_filters( 'upgrader_pre_install' );
+               remove_all_filters( 'upgrader_clear_destination' );
+               remove_all_filters( 'upgrader_post_install' );
+               remove_all_filters( 'upgrader_source_selection' );
+
+               add_filter( 'upgrader_source_selection', array( $this, 'check_package' ), 10, 2 );
 
                $this->skin->header();
 
@@ -1249,8 +2015,10 @@ class Language_Pack_Upgrader extends WP_Upgrader {
                $this->update_count = count( $language_updates );
                $this->update_current = 0;
 
-               // The filesystem's mkdir() is not recursive. Make sure WP_LANG_DIR exists,
-               // as we then may need to create a /plugins or /themes directory inside of it.
+               /*
+                * The filesystem's mkdir() is not recursive. Make sure WP_LANG_DIR exists,
+                * as we then may need to create a /plugins or /themes directory inside of it.
+                */
                $remote_destination = $wp_filesystem->find_folder( WP_LANG_DIR );
                if ( ! $wp_filesystem->exists( $remote_destination ) )
                        if ( ! $wp_filesystem->mkdir( $remote_destination, FS_CHMOD_DIR ) )
@@ -1295,18 +2063,30 @@ class Language_Pack_Upgrader extends WP_Upgrader {
                $this->skin->footer();
 
                // Clean up our hooks, in case something else does an upgrade on this connection.
-               remove_filter( 'upgrader_source_selection', array( &$this, 'check_package' ), 10, 2 );
+               remove_filter( 'upgrader_source_selection', array( $this, 'check_package' ) );
 
                if ( $parsed_args['clear_update_cache'] ) {
-                       wp_clean_themes_cache( true );
-                       wp_clean_plugins_cache( true );
-                       delete_site_transient( 'update_core' );
+                       wp_clean_update_cache();
                }
 
                return $results;
        }
 
-       function check_package( $source, $remote_source ) {
+       /**
+        * Check the package source to make sure there are .mo and .po files.
+        *
+        * Hooked to the {@see 'upgrader_source_selection'} filter by
+        * {@see Language_Pack_Upgrader::bulk_upgrade()}.
+        *
+        * @since 3.7.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param string|WP_Error $source
+        * @param string          $remote_source
+        */
+       public function check_package( $source, $remote_source ) {
                global $wp_filesystem;
 
                if ( is_wp_error( $source ) )
@@ -1324,18 +2104,33 @@ class Language_Pack_Upgrader extends WP_Upgrader {
                                $mo = true;
                }
 
-               if ( ! $mo || ! $po )
+               if ( ! $mo || ! $po ) {
                        return new WP_Error( 'incompatible_archive_pomo', $this->strings['incompatible_archive'],
-                               __( 'The language pack is missing either the <code>.po</code> or <code>.mo</code> files.' ) );
+                               /* translators: 1: .po 2: .mo */
+                               sprintf( __( 'The language pack is missing either the %1$s or %2$s files.' ),
+                                       '<code>.po</code>',
+                                       '<code>.mo</code>'
+                               )
+                       );
+               }
 
                return $source;
        }
 
-       function get_name_for_update( $update ) {
+       /**
+        * Get the name of an item being updated.
+        *
+        * @since 3.7.0
+        * @access public
+        *
+        * @param object $update The data for an update.
+        * @return string The name of the item being updated.
+        */
+       public function get_name_for_update( $update ) {
                switch ( $update->type ) {
                        case 'core':
                                return 'WordPress'; // Not translated
-                               break;
+
                        case 'theme':
                                $theme = wp_get_theme( $update->slug );
                                if ( $theme->exists() )
@@ -1343,7 +2138,7 @@ class Language_Pack_Upgrader extends WP_Upgrader {
                                break;
                        case 'plugin':
                                $plugin_data = get_plugins( '/' . $update->slug );
-                               $plugin_data = array_shift( $plugin_data );
+                               $plugin_data = reset( $plugin_data );
                                if ( $plugin_data )
                                        return $plugin_data['Name'];
                                break;
@@ -1354,15 +2149,24 @@ class Language_Pack_Upgrader extends WP_Upgrader {
 }
 
 /**
- * Core Upgrader class for WordPress. It allows for WordPress to upgrade itself in combination with the wp-admin/includes/update-core.php file
+ * Core class used for updating core.
+ *
+ * It allows for WordPress to upgrade itself in combination with
+ * the wp-admin/includes/update-core.php file.
  *
- * @package WordPress
- * @subpackage Upgrader
  * @since 2.8.0
+ *
+ * @see WP_Upgrader
  */
 class Core_Upgrader extends WP_Upgrader {
 
-       function upgrade_strings() {
+       /**
+        * Initialize the upgrade strings.
+        *
+        * @since 2.8.0
+        * @access public
+        */
+       public function upgrade_strings() {
                $this->strings['up_to_date'] = __('WordPress is at the latest version.');
                $this->strings['no_package'] = __('Update package not available.');
                $this->strings['downloading_package'] = __('Downloading update from <span class="code">%s</span>&#8230;');
@@ -1373,10 +2177,32 @@ class Core_Upgrader extends WP_Upgrader {
                $this->strings['rollback_was_required'] = __( 'Due to an error during updating, WordPress has rolled back to your previous version.' );
        }
 
-       function upgrade( $current, $args = array() ) {
+       /**
+        * Upgrade WordPress core.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        * @global callable           $_wp_filesystem_direct_method
+        *
+        * @param object $current Response object for whether WordPress is current.
+        * @param array  $args {
+        *        Optional. Arguments for upgrading WordPress core. Default empty array.
+        *
+        *        @type bool $pre_check_md5    Whether to check the file checksums before
+        *                                     attempting the upgrade. Default true.
+        *        @type bool $attempt_rollback Whether to attempt to rollback the chances if
+        *                                     there is a problem. Default false.
+        *        @type bool $do_rollback      Whether to perform this "upgrade" as a rollback.
+        *                                     Default false.
+        * }
+        * @return null|false|WP_Error False or WP_Error on failure, null on success.
+        */
+       public function upgrade( $current, $args = array() ) {
                global $wp_filesystem;
 
-               include ABSPATH . WPINC . '/version.php'; // $wp_version;
+               include( ABSPATH . WPINC . '/version.php' ); // $wp_version;
 
                $start_time = time();
 
@@ -1384,6 +2210,7 @@ class Core_Upgrader extends WP_Upgrader {
                        'pre_check_md5'    => true,
                        'attempt_rollback' => false,
                        'do_rollback'      => false,
+                       'allow_relaxed_file_ownership' => false,
                );
                $parsed_args = wp_parse_args( $args, $defaults );
 
@@ -1394,7 +2221,7 @@ class Core_Upgrader extends WP_Upgrader {
                if ( !isset( $current->response ) || $current->response == 'latest' )
                        return new WP_Error('up_to_date', $this->strings['up_to_date']);
 
-               $res = $this->fs_connect( array(ABSPATH, WP_CONTENT_DIR) );
+               $res = $this->fs_connect( array( ABSPATH, WP_CONTENT_DIR ), $parsed_args['allow_relaxed_file_ownership'] );
                if ( ! $res || is_wp_error( $res ) ) {
                        return $res;
                }
@@ -1452,9 +2279,11 @@ class Core_Upgrader extends WP_Upgrader {
                        $try_rollback = false;
                        if ( is_wp_error( $result ) ) {
                                $error_code = $result->get_error_code();
-                               // Not all errors are equal. These codes are critical: copy_failed__copy_dir,
-                               // mkdir_failed__copy_dir, copy_failed__copy_dir_retry, and disk_full.
-                               // do_rollback allows for update_core() to trigger a rollback if needed.
+                               /*
+                                * Not all errors are equal. These codes are critical: copy_failed__copy_dir,
+                                * mkdir_failed__copy_dir, copy_failed__copy_dir_retry, and disk_full.
+                                * do_rollback allows for update_core() to trigger a rollback if needed.
+                                */
                                if ( false !== strpos( $error_code, 'do_rollback' ) )
                                        $try_rollback = true;
                                elseif ( false !== strpos( $error_code, '__copy_dir' ) )
@@ -1489,6 +2318,7 @@ class Core_Upgrader extends WP_Upgrader {
                                'success'          => true,
                                'fs_method'        => $wp_filesystem->method,
                                'fs_method_forced' => defined( 'FS_METHOD' ) || has_filter( 'filesystem_method' ),
+                               'fs_method_direct' => !empty( $GLOBALS['_wp_filesystem_direct_method'] ) ? $GLOBALS['_wp_filesystem_direct_method'] : '',
                                'time_taken'       => time() - $start_time,
                                'reported'         => $wp_version,
                                'attempted'        => $current->version,
@@ -1518,9 +2348,19 @@ class Core_Upgrader extends WP_Upgrader {
                return $result;
        }
 
-       // Determines if this WordPress Core version should update to $offered_ver or not
-       static function should_update_to_version( $offered_ver /* x.y.z */ ) {
-               include ABSPATH . WPINC . '/version.php'; // $wp_version; // x.y.z
+       /**
+        * Determines if this WordPress Core version should update to an offered version or not.
+        *
+        * @since 3.7.0
+        * @access public
+        *
+        * @static
+        *
+        * @param string $offered_ver The offered version, of the format x.y.z.
+        * @return bool True if we should update to the offered version, otherwise false.
+        */
+       public static function should_update_to_version( $offered_ver ) {
+               include( ABSPATH . WPINC . '/version.php' ); // $wp_version; // x.y.z
 
                $current_branch = implode( '.', array_slice( preg_split( '/[.-]/', $wp_version  ), 0, 2 ) ); // x.y
                $new_branch     = implode( '.', array_slice( preg_split( '/[.-]/', $offered_ver ), 0, 2 ) ); // x.y
@@ -1584,7 +2424,7 @@ class Core_Upgrader extends WP_Upgrader {
                         */
                        if ( ! apply_filters( 'allow_dev_auto_core_updates', $upgrade_dev ) )
                                return false;
-                       // else fall through to minor + major branches below
+                       // Else fall through to minor + major branches below.
                }
 
                // 4: Minor In-branch updates (3.7.0 -> 3.7.1 -> 3.7.2 -> 3.7.4)
@@ -1617,7 +2457,18 @@ class Core_Upgrader extends WP_Upgrader {
                return false;
        }
 
-       function check_files() {
+       /**
+        * Compare the disk file checksums against the expected checksums.
+        *
+        * @since 3.7.0
+        * @access public
+        *
+        * @global string $wp_version
+        * @global string $wp_local_package
+        *
+        * @return bool True if the checksums match, otherwise false.
+        */
+       public function check_files() {
                global $wp_version, $wp_local_package;
 
                $checksums = get_core_checksums( $wp_version, isset( $wp_local_package ) ? $wp_local_package : 'en_US' );
@@ -1638,18 +2489,52 @@ class Core_Upgrader extends WP_Upgrader {
 }
 
 /**
- * Upgrade Skin helper for File uploads. This class handles the upload process and passes it as if it's a local file to the Upgrade/Installer functions.
+ * Core class used for handling file uploads.
+ *
+ * This class handles the upload process and passes it as if it's a local file
+ * to the Upgrade/Installer functions.
  *
- * @package WordPress
- * @subpackage Upgrader
  * @since 2.8.0
  */
 class File_Upload_Upgrader {
-       var $package;
-       var $filename;
-       var $id = 0;
 
-       function __construct($form, $urlholder) {
+       /**
+        * The full path to the file package.
+        *
+        * @since 2.8.0
+        * @access public
+        * @var string $package
+        */
+       public $package;
+
+       /**
+        * The name of the file.
+        *
+        * @since 2.8.0
+        * @access public
+        * @var string $filename
+        */
+       public $filename;
+
+       /**
+        * The ID of the attachment post for this file.
+        *
+        * @since 3.3.0
+        * @access public
+        * @var int $id
+        */
+       public $id = 0;
+
+       /**
+        * Construct the upgrader for a form.
+        *
+        * @since 2.8.0
+        * @access public
+        *
+        * @param string $form      The name of the form the file was uploaded from.
+        * @param string $urlholder The name of the `GET` parameter that holds the filename.
+        */
+       public function __construct( $form, $urlholder ) {
 
                if ( empty($_FILES[$form]['name']) && empty($_GET[$urlholder]) )
                        wp_die(__('Please select a file'));
@@ -1675,11 +2560,11 @@ class File_Upload_Upgrader {
                                'post_status' => 'private'
                        );
 
-                       // Save the data
+                       // Save the data.
                        $this->id = wp_insert_attachment( $object, $file['file'] );
 
-                       // schedule a cleanup for 2 hours from now in case of failed install
-                       wp_schedule_single_event( time() + 7200, 'upgrader_scheduled_cleanup', array( $this->id ) );
+                       // Schedule a cleanup for 2 hours from now in case of failed install.
+                       wp_schedule_single_event( time() + 2 * HOUR_IN_SECONDS, 'upgrader_scheduled_cleanup', array( $this->id ) );
 
                } elseif ( is_numeric( $_GET[$urlholder] ) ) {
                        // Numeric Package = previously uploaded file, see above.
@@ -1700,7 +2585,15 @@ class File_Upload_Upgrader {
                }
        }
 
-       function cleanup() {
+       /**
+        * Delete the attachment/uploaded file.
+        *
+        * @since 3.2.2
+        * @access public
+        *
+        * @return bool Whether the cleanup was successful.
+        */
+       public function cleanup() {
                if ( $this->id )
                        wp_delete_attachment( $this->id );
 
@@ -1712,10 +2605,8 @@ class File_Upload_Upgrader {
 }
 
 /**
- * The WordPress automatic background updater.
+ * Core class used for handling automatic background updates.
  *
- * @package WordPress
- * @subpackage Upgrader
  * @since 3.7.0
  */
 class WP_Automatic_Updater {
@@ -1724,6 +2615,7 @@ class WP_Automatic_Updater {
         * Tracks update results during processing.
         *
         * @var array
+        * @access protected
         */
        protected $update_results = array();
 
@@ -1731,13 +2623,14 @@ class WP_Automatic_Updater {
         * Whether the entire automatic updater is disabled.
         *
         * @since 3.7.0
+        * @access public
         */
        public function is_disabled() {
                // Background updates are disabled if you don't want file changes.
                if ( defined( 'DISALLOW_FILE_MODS' ) && DISALLOW_FILE_MODS )
                        return true;
 
-               if ( defined( 'WP_INSTALLING' ) )
+               if ( wp_installing() )
                        return true;
 
                // More fine grained control can be done through the WP_AUTO_UPDATE_CORE constant and filters.
@@ -1771,6 +2664,7 @@ class WP_Automatic_Updater {
         * how things get updated.
         *
         * @since 3.7.0
+        * @access public
         *
         * @param string $context The filesystem path to check, in addition to ABSPATH.
         */
@@ -1823,6 +2717,9 @@ class WP_Automatic_Updater {
         * Tests to see if we can and should update a specific item.
         *
         * @since 3.7.0
+        * @access public
+        *
+        * @global wpdb $wpdb WordPress database abstraction object.
         *
         * @param string $type    The type of update being checked: 'core', 'theme',
         *                        'plugin', 'translation'.
@@ -1837,8 +2734,14 @@ class WP_Automatic_Updater {
                if ( $this->is_disabled() )
                        return false;
 
+               // Only relax the filesystem checks when the update doesn't include new files
+               $allow_relaxed_file_ownership = false;
+               if ( 'core' == $type && isset( $item->new_files ) && ! $item->new_files ) {
+                       $allow_relaxed_file_ownership = true;
+               }
+
                // If we can't do an auto core update, we may still be able to email the user.
-               if ( ! $skin->request_filesystem_credentials( false, $context ) || $this->is_vcs_checkout( $context ) ) {
+               if ( ! $skin->request_filesystem_credentials( false, $context, $allow_relaxed_file_ownership ) || $this->is_vcs_checkout( $context ) ) {
                        if ( 'core' == $type )
                                $this->send_core_update_notification_email( $item );
                        return false;
@@ -1853,15 +2756,15 @@ class WP_Automatic_Updater {
                /**
                 * Filter whether to automatically update core, a plugin, a theme, or a language.
                 *
-                * The dynamic portion of the hook name, $type, refers to the type of update
+                * The dynamic portion of the hook name, `$type`, refers to the type of update
                 * being checked. Can be 'core', 'theme', 'plugin', or 'translation'.
                 *
                 * Generally speaking, plugins, themes, and major core versions are not updated
                 * by default, while translations and minor and development versions for core
                 * are updated by default.
                 *
-                * See the allow_dev_auto_core_updates, allow_minor_auto_core_updates, and
-                * allow_major_auto_core_updates filters for a more straightforward way to
+                * See the {@see 'allow_dev_auto_core_updates', {@see 'allow_minor_auto_core_updates'},
+                * and {@see 'allow_major_auto_core_updates'} filters for a more straightforward way to
                 * adjust core updates.
                 *
                 * @since 3.7.0
@@ -1898,11 +2801,11 @@ class WP_Automatic_Updater {
         * Notifies an administrator of a core update.
         *
         * @since 3.7.0
+        * @access protected
         *
         * @param object $item The update offer.
         */
        protected function send_core_update_notification_email( $item ) {
-               $notify   = true;
                $notified = get_site_option( 'auto_core_update_notified' );
 
                // Don't notify if we've already notified the same email address of the same version.
@@ -1942,9 +2845,12 @@ class WP_Automatic_Updater {
         * Update an item, if appropriate.
         *
         * @since 3.7.0
+        * @access public
         *
         * @param string $type The type of update being checked: 'core', 'theme', 'plugin', 'translation'.
         * @param object $item The update offer.
+        *
+        * @return null|WP_Error
         */
        public function update( $type, $item ) {
                $skin = new Automatic_Upgrader_Skin;
@@ -1974,6 +2880,18 @@ class WP_Automatic_Updater {
                if ( ! $this->should_update( $type, $item, $context ) )
                        return false;
 
+               /**
+                * Fires immediately prior to an auto-update.
+                *
+                * @since 4.4.0
+                *
+                * @param string $type    The type of update being checked: 'core', 'theme', 'plugin', or 'translation'.
+                * @param object $item    The update offer.
+                * @param string $context The filesystem context (a path) against which filesystem access and status
+                *                        should be checked.
+                */
+               do_action( 'pre_auto_update', $type, $item, $context );
+
                $upgrader_item = $item;
                switch ( $type ) {
                        case 'core':
@@ -1999,19 +2917,28 @@ class WP_Automatic_Updater {
                                break;
                }
 
+               $allow_relaxed_file_ownership = false;
+               if ( 'core' == $type && isset( $item->new_files ) && ! $item->new_files ) {
+                       $allow_relaxed_file_ownership = true;
+               }
+
                // Boom, This sites about to get a whole new splash of paint!
                $upgrade_result = $upgrader->upgrade( $upgrader_item, array(
                        'clear_update_cache' => false,
-                       'pre_check_md5'      => false, /* always use partial builds if possible for core updates */
-                       'attempt_rollback'   => true, /* only available for core updates */
+                       // Always use partial builds if possible for core updates.
+                       'pre_check_md5'      => false,
+                       // Only available for core updates.
+                       'attempt_rollback'   => true,
+                       // Allow relaxed file ownership in some scenarios
+                       'allow_relaxed_file_ownership' => $allow_relaxed_file_ownership,
                ) );
 
-               // if the filesystem is unavailable, false is returned.
+               // If the filesystem is unavailable, false is returned.
                if ( false === $upgrade_result ) {
                        $upgrade_result = new WP_Error( 'fs_unavailable', __( 'Could not access filesystem.' ) );
                }
 
-               // Core doesn't output this, so lets append it so we don't get confused
+               // Core doesn't output this, so let's append it so we don't get confused.
                if ( 'core' == $type ) {
                        if ( is_wp_error( $upgrade_result ) ) {
                                $skin->error( __( 'Installation Failed' ), $upgrade_result );
@@ -2034,6 +2961,10 @@ class WP_Automatic_Updater {
         * Kicks off the background update process, looping through all pending updates.
         *
         * @since 3.7.0
+        * @access public
+        *
+        * @global wpdb   $wpdb
+        * @global string $wp_version
         */
        public function run() {
                global $wpdb, $wp_version;
@@ -2061,7 +2992,7 @@ class WP_Automatic_Updater {
                                return;
                }
 
-               // Update the lock, as by this point we've definately got a lock, just need to fire the actions
+               // Update the lock, as by this point we've definitely got a lock, just need to fire the actions
                update_option( $lock_name, time() );
 
                // Don't automatically run these thins, as we'll handle it ourselves
@@ -2125,9 +3056,7 @@ class WP_Automatic_Updater {
                        }
 
                        // Clear existing caches
-                       wp_clean_plugins_cache();
-                       wp_clean_themes_cache();
-                       delete_site_transient( 'update_core' );
+                       wp_clean_update_cache();
 
                        wp_version_check();  // check for Core updates
                        wp_update_themes();  // Check for Theme updates
@@ -2171,7 +3100,12 @@ class WP_Automatic_Updater {
         * If we tried to perform a core update, check if we should send an email,
         * and if we need to avoid processing future updates.
         *
-        * @param object $update_result The result of the core update. Includes the update offer and result.
+        * @since Unknown
+        * @access protected
+        *
+        * @global string $wp_version
+        *
+        * @param object|WP_Error $update_result The result of the core update. Includes the update offer and result.
         */
        protected function after_core_update( $update_result ) {
                global $wp_version;
@@ -2257,6 +3191,9 @@ class WP_Automatic_Updater {
         * Sends an email upon the completion or failure of a background core update.
         *
         * @since 3.7.0
+        * @access protected
+        *
+        * @global string $wp_version
         *
         * @param string $type        The type of email to send. Can be one of 'success', 'fail', 'manual', 'critical'.
         * @param object $core_update The update offer that was attempted.
@@ -2368,7 +3305,7 @@ class WP_Automatic_Updater {
                $critical_support = 'critical' === $type && ! empty( $core_update->support_email );
                if ( $critical_support ) {
                        // Support offer if available.
-                       $body .= "\n\n" . sprintf( __( "The WordPress team is willing to help you. Forward this email to %s and the¬†team¬†will work with you to make sure your site is working." ), $core_update->support_email );
+                       $body .= "\n\n" . sprintf( __( "The WordPress team is willing to help you. Forward this email to %s and the team will work with you to make sure your site is working." ), $core_update->support_email );
                } else {
                        // Add a note about the support forums.
                        $body .= "\n\n" . __( 'If you experience any issues or need support, the volunteers in the WordPress.org support forums may be able to help.' );
@@ -2454,6 +3391,7 @@ class WP_Automatic_Updater {
         * Prepares and sends an email of a full log of background update results, useful for debugging and geekery.
         *
         * @since 3.7.0
+        * @access protected
         */
        protected function send_debug_email() {
                $update_count = 0;
@@ -2515,26 +3453,27 @@ class WP_Automatic_Updater {
 
                $site_title = wp_specialchars_decode( get_bloginfo( 'name' ), ENT_QUOTES );
                if ( $failures ) {
-                       $body[] = __( "
-BETA TESTING?
+                       $body[] = trim( __(
+"BETA TESTING?
 =============
 
 This debugging email is sent when you are using a development version of WordPress.
 
 If you think these failures might be due to a bug in WordPress, could you report it?
  * Open a thread in the support forums: https://wordpress.org/support/forum/alphabeta
- * Or, if you're comfortable writing a bug report: http://core.trac.wordpress.org/
+ * Or, if you're comfortable writing a bug report: https://core.trac.wordpress.org/
 
-Thanks! -- The WordPress Team" );
+Thanks! -- The WordPress Team" ) );
+                       $body[] = '';
 
                        $subject = sprintf( __( '[%s] There were failures during background updates' ), $site_title );
                } else {
                        $subject = sprintf( __( '[%s] Background updates have finished' ), $site_title );
                }
 
-               $title = __( 'UPDATE LOG' );
-               $body[] = $title;
-               $body[] = str_repeat( '=', strlen( $title ) );
+               $body[] = trim( __(
+'UPDATE LOG
+==========' ) );
                $body[] = '';
 
                foreach ( array( 'core', 'plugin', 'theme', 'translation' ) as $type ) {