Language_Pack_Upgrader::bulk_upgrade

	public function bulk_upgrade( $language_updates = array(), $args = array() ) {
		global $wp_filesystem;

		$defaults    = array(
			'clear_update_cache' => true,
		);
		$parsed_args = wp_parse_args( $args, $defaults );

		$this->init();
		$this->upgrade_strings();

		if ( ! $language_updates ) {
			$language_updates = wp_get_translation_updates();
		}

		if ( empty( $language_updates ) ) {
			$this->skin->header();
			$this->skin->set_result( true );
			$this->skin->feedback( 'up_to_date' );
			$this->skin->bulk_footer();
			$this->skin->footer();
			return true;
		}

		if ( 'upgrader_process_complete' === current_filter() ) {
			$this->skin->feedback( 'starting_upgrade' );
		}

		// 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();

		// Connect to the filesystem first.
		$res = $this->fs_connect( array( WP_CONTENT_DIR, WP_LANG_DIR ) );
		if ( ! $res ) {
			$this->skin->footer();
			return false;
		}

		$results = array();

		$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.
		 */
		$remote_destination = $wp_filesystem->find_folder( WP_LANG_DIR );
		if ( ! $wp_filesystem->exists( $remote_destination ) ) {
			if ( ! $wp_filesystem->mkdir( $remote_destination, FS_CHMOD_DIR ) ) {
				return new WP_Error( 'mkdir_failed_lang_dir', $this->strings['mkdir_failed'], $remote_destination );
			}
		}

		$language_updates_results = array();

		foreach ( $language_updates as $language_update ) {

			$this->skin->language_update = $language_update;

			$destination = WP_LANG_DIR;
			if ( 'plugin' === $language_update->type ) {
				$destination .= '/plugins';
			} elseif ( 'theme' === $language_update->type ) {
				$destination .= '/themes';
			}

			$this->update_current++;

			$options = array(
				'package'                     => $language_update->package,
				'destination'                 => $destination,
				'clear_destination'           => true,
				'abort_if_destination_exists' => false, // We expect the destination to exist.
				'clear_working'               => true,
				'is_multi'                    => true,
				'hook_extra'                  => array(
					'language_update_type' => $language_update->type,
					'language_update'      => $language_update,
				),
			);

			$result = $this->run( $options );

			$results[] = $this->result;

			// Prevent credentials auth screen from displaying multiple times.
			if ( false === $result ) {
				break;
			}

			$language_updates_results[] = array(
				'language' => $language_update->language,
				'type'     => $language_update->type,
				'slug'     => isset( $language_update->slug ) ? $language_update->slug : 'default',
				'version'  => $language_update->version,
			);
		}

		// Remove upgrade hooks which are not required for translation updates.
		remove_action( 'upgrader_process_complete', array( 'Language_Pack_Upgrader', 'async_upgrade' ), 20 );
		remove_action( 'upgrader_process_complete', 'wp_version_check' );
		remove_action( 'upgrader_process_complete', 'wp_update_plugins' );
		remove_action( 'upgrader_process_complete', 'wp_update_themes' );

		/** This action is documented in wp-admin/includes/class-wp-upgrader.php */
		do_action(
			'upgrader_process_complete',
			$this,
			array(
				'action'       => 'update',
				'type'         => 'translation',
				'bulk'         => true,
				'translations' => $language_updates_results,
			)
		);

		// Re-add upgrade hooks.
		add_action( 'upgrader_process_complete', array( 'Language_Pack_Upgrader', 'async_upgrade' ), 20 );
		add_action( 'upgrader_process_complete', 'wp_version_check', 10, 0 );
		add_action( 'upgrader_process_complete', 'wp_update_plugins', 10, 0 );
		add_action( 'upgrader_process_complete', 'wp_update_themes', 10, 0 );

		$this->skin->bulk_footer();

		$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' ) );

		if ( $parsed_args['clear_update_cache'] ) {
			wp_clean_update_cache();
		}

		return $results;
	}