Ticket #43941: 43941.diff

src/wp-includes/meta.php

@@ -532 +532 @@
                         return array_map( 'maybe_unserialize', $meta_cache[ $meta_key ] );
                 }
         }
-
-        if ( $single ) {
-                return '';
-        } else {
-                return array();
+        $object_subtype = get_object_subtype( $meta_type, $object_id );
+        $default        = get_metadata_default( $meta_type, $meta_key, $object_subtype );
+        if ( ! $single ) {
+                $default_value = (array) $default_value;
         }
+        return $default;
 }
 
 /**
@@ -1045 +1045 @@
  *                                     Valid values are 'string', 'boolean', 'integer', and 'number'.
  *     @type string $description       A description of the data attached to this meta key.
  *     @type bool   $single            Whether the meta key has one value per object, or an array of values per object.
+ *     @type mixed  $default           Optional. Default value to return if the meta key does not exist.
  *     @type string $sanitize_callback A function or method to call when sanitizing `$meta_key` data.
  *     @type string $auth_callback     Optional. A function or method to call when performing edit_post_meta, add_post_meta, and delete_post_meta capability checks.
  *     @type bool   $show_in_rest      Whether data associated with this meta key can be considered public.
@@ -1070 +1071 @@
                 'sanitize_callback' => null,
                 'auth_callback'     => null,
                 'show_in_rest'      => false,
+                'default'           => null,
         );
 
         // There used to be individual args for sanitize and auth callbacks
@@ -1132 +1134 @@
                 }
         }
 
+        if ( null !== $args['default'] ) {
+                if ( ! empty( $object_subtype ) ) {
+                        add_filter( "default_{$object_type}_meta_{$meta_key}_for_{$object_subtype}", 'filter_default_meta', 10, 4 );
+                } else {
+                        add_filter( "default_{$object_type}_meta_{$meta_key}", 'filter_default_meta', 10, 4 );
+                }
+        }
+
         // Global registry only contains meta keys registered with the array of arguments added in 4.6.0.
         if ( ! $has_old_auth_cb && ! $has_old_sanitize_cb ) {
                 unset( $args['object_subtype'] );
@@ -1145 +1155 @@
 }
 
 /**
+ * Sanitize meta value.
+ *
+ * @since 3.1.3
+ * @since 5.0.0 The `$object_subtype` parameter was added.
+ *
+ * @param string $meta_key       Meta key.
+ * @param mixed  $meta_value     Meta value to sanitize.
+ * @param string $object_type    Type of object the meta is registered to.
+ *
+ * @return mixed Default Value $default_value.
+ */
+function get_metadata_default( $meta_key, $object_type, $object_subtype = '' ) {
+
+        $default_value = '';
+        if ( ! empty( $object_subtype ) && has_filter( "sanitize_{$object_type}_meta_{$meta_key}_for_{$object_subtype}" ) ) {
+
+                /**
+                 *
+                 * The dynamic portions of the hook name, `$object_type`, `$meta_key`,
+                 * and `$object_subtype`, refer to the metadata object type (comment, post, term or user),
+                 * the meta key value, and the object subtype respectively.
+                 *
+                 * @since 5.0.0
+                 *
+                 * @param mixed  $default_value  Default value.
+                 * @param string $meta_key       Meta key.
+                 * @param string $object_type    Object type.
+                 * @param string $object_subtype Object subtype.
+                 */
+                return apply_filters( "default_{$object_type}_meta_{$meta_key}_for_{$object_subtype}", $default_value, $meta_key, $object_type, $object_subtype );
+        }
+
+        /**
+         *
+         * The dynamic portions of the hook name, `$meta_type`, and `$meta_key`,
+         * refer to the metadata object type (comment, post, or user) and the meta
+         * key value, respectively.
+         *
+         * @since 5.5.0
+         *
+         * @param mixed  $default_value      Default value.
+         * @param string $meta_key        Meta key.
+         * @param string $object_type     Object type.
+         * @param string $object_subtype Object subtype.
+         */
+        return apply_filters( "default_{$object_type}_meta_{$meta_key}", $default_value, $meta_key, $object_type );
+}
+
+/**
  * Checks if a meta key is registered.
  *
  * @since 4.6.0
@@ -1199 +1258 @@
                 }
         }
 
+        if ( isset( $args['default'] ) && null !== $args['default'] ) {
+                if ( ! empty( $object_subtype ) ) {
+                        remove_filter( "default_{$object_type}_meta_{$meta_key}_for_{$object_subtype}", 'filter_default_meta' );
+                } else {
+                        remove_filter( "default_{$object_type}_meta_{$meta_key}", 'filter_default_meta' );
+                }
+        }
+
         unset( $wp_meta_keys[ $object_type ][ $object_subtype ][ $meta_key ] );
 
         // Do some clean up
@@ -1360 +1427 @@
          */
         return apply_filters( "get_object_subtype_{$object_type}", $object_subtype, $object_id );
 }
+
+/**
+ * @param $default_value
+ * @param $meta_key
+ * @param $object_type
+ * @param string $object_subtype
+ *
+ * @return mixed
+ */
+function filter_default_meta( $default_value, $meta_key, $object_type, $object_subtype = '' ) {
+        global $wp_meta_keys;
+
+        if ( ! is_array( $wp_meta_keys ) ) {
+                $wp_meta_keys = [];
+        }
+
+
+        if ( isset( $wp_meta_keys[ $object_type ][ $object_subtype ][ $meta_key ]['default'] ) &&
+             null !== $wp_meta_keys[ $object_type ][ $object_subtype ][ $meta_key ]['default'] ) {
+                $default_value = $wp_meta_keys[ $object_type ][ $object_subtype ][ $meta_key ]['default'];
+        }
+
+        return $default_value;
+}
+ No newline at end of file