diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-includes/customize/class-wp-customize-partial.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/customize/class-wp-customize-partial.php	Mon Oct 14 17:39:30 2019 +0200
@@ -0,0 +1,311 @@
+<?php
+/**
+ * Customize API: WP_Customize_Partial class
+ *
+ * @package WordPress
+ * @subpackage Customize
+ * @since 4.5.0
+ */
+
+/**
+ * Core Customizer class for implementing selective refresh partials.
+ *
+ * Representation of a rendered region in the previewed page that gets
+ * selectively refreshed when an associated setting is changed.
+ * This class is analogous of WP_Customize_Control.
+ *
+ * @since 4.5.0
+ */
+class WP_Customize_Partial {
+
+	/**
+	 * Component.
+	 *
+	 * @since 4.5.0
+	 * @var WP_Customize_Selective_Refresh
+	 */
+	public $component;
+
+	/**
+	 * Unique identifier for the partial.
+	 *
+	 * If the partial is used to display a single setting, this would generally
+	 * be the same as the associated setting's ID.
+	 *
+	 * @since 4.5.0
+	 * @var string
+	 */
+	public $id;
+
+	/**
+	 * Parsed ID.
+	 *
+	 * @since 4.5.0
+	 * @var array {
+	 *     @type string $base ID base.
+	 *     @type array  $keys Keys for multidimensional.
+	 * }
+	 */
+	protected $id_data = array();
+
+	/**
+	 * Type of this partial.
+	 *
+	 * @since 4.5.0
+	 * @var string
+	 */
+	public $type = 'default';
+
+	/**
+	 * The jQuery selector to find the container element for the partial.
+	 *
+	 * @since 4.5.0
+	 * @var string
+	 */
+	public $selector;
+
+	/**
+	 * IDs for settings tied to the partial.
+	 *
+	 * @since 4.5.0
+	 * @var array
+	 */
+	public $settings;
+
+	/**
+	 * The ID for the setting that this partial is primarily responsible for rendering.
+	 *
+	 * If not supplied, it will default to the ID of the first setting.
+	 *
+	 * @since 4.5.0
+	 * @var string
+	 */
+	public $primary_setting;
+
+	/**
+	 * Capability required to edit this partial.
+	 *
+	 * Normally this is empty and the capability is derived from the capabilities
+	 * of the associated `$settings`.
+	 *
+	 * @since 4.5.0
+	 * @var string
+	 */
+	public $capability;
+
+	/**
+	 * Render callback.
+	 *
+	 * @since 4.5.0
+	 * @see WP_Customize_Partial::render()
+	 * @var callable Callback is called with one argument, the instance of
+	 *                 WP_Customize_Partial. The callback can either echo the
+	 *                 partial or return the partial as a string, or return false if error.
+	 */
+	public $render_callback;
+
+	/**
+	 * Whether the container element is included in the partial, or if only the contents are rendered.
+	 *
+	 * @since 4.5.0
+	 * @var bool
+	 */
+	public $container_inclusive = false;
+
+	/**
+	 * Whether to refresh the entire preview in case a partial cannot be refreshed.
+	 *
+	 * A partial render is considered a failure if the render_callback returns false.
+	 *
+	 * @since 4.5.0
+	 * @var bool
+	 */
+	public $fallback_refresh = true;
+
+	/**
+	 * Constructor.
+	 *
+	 * Supplied `$args` override class property defaults.
+	 *
+	 * If `$args['settings']` is not defined, use the $id as the setting ID.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param WP_Customize_Selective_Refresh $component Customize Partial Refresh plugin instance.
+	 * @param string                         $id        Control ID.
+	 * @param array                          $args      {
+	 *     Optional. Arguments to override class property defaults.
+	 *
+	 *     @type array|string $settings All settings IDs tied to the partial. If undefined, `$id` will be used.
+	 * }
+	 */
+	public function __construct( WP_Customize_Selective_Refresh $component, $id, $args = array() ) {
+		$keys = array_keys( get_object_vars( $this ) );
+		foreach ( $keys as $key ) {
+			if ( isset( $args[ $key ] ) ) {
+				$this->$key = $args[ $key ];
+			}
+		}
+
+		$this->component       = $component;
+		$this->id              = $id;
+		$this->id_data['keys'] = preg_split( '/\[/', str_replace( ']', '', $this->id ) );
+		$this->id_data['base'] = array_shift( $this->id_data['keys'] );
+
+		if ( empty( $this->render_callback ) ) {
+			$this->render_callback = array( $this, 'render_callback' );
+		}
+
+		// Process settings.
+		if ( ! isset( $this->settings ) ) {
+			$this->settings = array( $id );
+		} else if ( is_string( $this->settings ) ) {
+			$this->settings = array( $this->settings );
+		}
+
+		if ( empty( $this->primary_setting ) ) {
+			$this->primary_setting = current( $this->settings );
+		}
+	}
+
+	/**
+	 * Retrieves parsed ID data for multidimensional setting.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @return array {
+	 *     ID data for multidimensional partial.
+	 *
+	 *     @type string $base ID base.
+	 *     @type array  $keys Keys for multidimensional array.
+	 * }
+	 */
+	final public function id_data() {
+		return $this->id_data;
+	}
+
+	/**
+	 * Renders the template partial involving the associated settings.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param array $container_context Optional. Array of context data associated with the target container (placement).
+	 *                                 Default empty array.
+	 * @return string|array|false The rendered partial as a string, raw data array (for client-side JS template),
+	 *                            or false if no render applied.
+	 */
+	final public function render( $container_context = array() ) {
+		$partial  = $this;
+		$rendered = false;
+
+		if ( ! empty( $this->render_callback ) ) {
+			ob_start();
+			$return_render = call_user_func( $this->render_callback, $this, $container_context );
+			$ob_render = ob_get_clean();
+
+			if ( null !== $return_render && '' !== $ob_render ) {
+				_doing_it_wrong( __FUNCTION__, __( 'Partial render must echo the content or return the content string (or array), but not both.' ), '4.5.0' );
+			}
+
+			/*
+			 * Note that the string return takes precedence because the $ob_render may just\
+			 * include PHP warnings or notices.
+			 */
+			$rendered = null !== $return_render ? $return_render : $ob_render;
+		}
+
+		/**
+		 * Filters partial rendering.
+		 *
+		 * @since 4.5.0
+		 *
+		 * @param string|array|false   $rendered          The partial value. Default false.
+		 * @param WP_Customize_Partial $partial           WP_Customize_Setting instance.
+		 * @param array                $container_context Optional array of context data associated with
+		 *                                                the target container.
+		 */
+		$rendered = apply_filters( 'customize_partial_render', $rendered, $partial, $container_context );
+
+		/**
+		 * Filters partial rendering for a specific partial.
+		 *
+		 * The dynamic portion of the hook name, `$partial->ID` refers to the partial ID.
+		 *
+		 * @since 4.5.0
+		 *
+		 * @param string|array|false   $rendered          The partial value. Default false.
+		 * @param WP_Customize_Partial $partial           WP_Customize_Setting instance.
+		 * @param array                $container_context Optional array of context data associated with
+		 *                                                the target container.
+		 */
+		$rendered = apply_filters( "customize_partial_render_{$partial->id}", $rendered, $partial, $container_context );
+
+		return $rendered;
+	}
+
+	/**
+	 * Default callback used when invoking WP_Customize_Control::render().
+	 *
+	 * Note that this method may echo the partial *or* return the partial as
+	 * a string or array, but not both. Output buffering is performed when this
+	 * is called. Subclasses can override this with their specific logic, or they
+	 * may provide an 'render_callback' argument to the constructor.
+	 *
+	 * This method may return an HTML string for straight DOM injection, or it
+	 * may return an array for supporting Partial JS subclasses to render by
+	 * applying to client-side templating.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param WP_Customize_Partial $partial Partial.
+	 * @param array                $context Context.
+	 * @return string|array|false
+	 */
+	public function render_callback( WP_Customize_Partial $partial, $context = array() ) {
+		unset( $partial, $context );
+		return false;
+	}
+
+	/**
+	 * Retrieves the data to export to the client via JSON.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @return array Array of parameters passed to the JavaScript.
+	 */
+	public function json() {
+		$exports = array(
+			'settings'           => $this->settings,
+			'primarySetting'     => $this->primary_setting,
+			'selector'           => $this->selector,
+			'type'               => $this->type,
+			'fallbackRefresh'    => $this->fallback_refresh,
+			'containerInclusive' => $this->container_inclusive,
+		);
+		return $exports;
+	}
+
+	/**
+	 * Checks if the user can refresh this partial.
+	 *
+	 * Returns false if the user cannot manipulate one of the associated settings,
+	 * or if one of the associated settings does not exist.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @return bool False if user can't edit one of the related settings,
+	 *                    or if one of the associated settings does not exist.
+	 */
+	final public function check_capabilities() {
+		if ( ! empty( $this->capability ) && ! current_user_can( $this->capability ) ) {
+			return false;
+		}
+		foreach ( $this->settings as $setting_id ) {
+			$setting = $this->component->manager->get_setting( $setting_id );
+			if ( ! $setting || ! $setting->check_capabilities() ) {
+				return false;
+			}
+		}
+		return true;
+	}
+}