Fix: Core abilities invalid schemas (has examples and returns empty array intested of object).

Theis commit fixes two issues with the core abilities schemas we have:
- They have examples on the schema with is not complient with the version draft-04 of schema JSON we are using.
- The top level defaults are defined as an empty array and they are of type object, but a php empty array gets JSON serialized and returned in the rest API as [] instead of {}, causing problems on the client validation.

Developed in #10510.

Props jorgefilipecosta, gziolo.
Fixes #64252.

git-svn-id: https://develop.svn.wordpress.org/trunk@61244 602fd350-edb4-49c9-b593-d223f7449a82

Author: jorgefilipecosta

src/wp-includes/abilities.php

@@ -220,7 +220,6 @@ function wp_register_core_abilities(): void {
 					'db_server_info' => array(
 						'type'        => 'string',
 						'description' => __( 'The database server vendor and version string reported by the driver.' ),
-						'examples'    => array( '8.0.34', '10.11.6-MariaDB' ),
 					),
 					'wp_version'     => array(
 						'type'        => 'string',

src/wp-includes/rest-api/endpoints/class-wp-rest-abilities-v1-list-controller.php

@@ -194,6 +194,27 @@ public function get_item_permissions_check( $request ) {
 		return current_user_can( 'read' );
 	}
 
+	/**
+	 * Normalizes schema empty object defaults.
+	 *
+	 * Converts empty array defaults to objects when the schema type is 'object'
+	 * to ensure proper JSON serialization as {} instead of [].
+	 *
+	 * @since 6.9.0
+	 *
+	 * @param array<string, mixed> $schema The schema array.
+	 * @return array<string, mixed> The normalized schema.
+	 */
+	private function normalize_schema_empty_object_defaults( array $schema ): array {
+		if ( isset( $schema['type'] ) && 'object' === $schema['type'] && isset( $schema['default'] ) ) {
+			$default = $schema['default'];
+			if ( is_array( $default ) && empty( $default ) ) {
+				$schema['default'] = (object) $default;
+			}
+		}
+		return $schema;
+	}
+
 	/**
 	 * Prepares an ability for response.
 	 *
@@ -209,8 +230,8 @@ public function prepare_item_for_response( $ability, $request ) {
 			'label'         => $ability->get_label(),
 			'description'   => $ability->get_description(),
 			'category'      => $ability->get_category(),
-			'input_schema'  => $ability->get_input_schema(),
-			'output_schema' => $ability->get_output_schema(),
+			'input_schema'  => $this->normalize_schema_empty_object_defaults( $ability->get_input_schema() ),
+			'output_schema' => $this->normalize_schema_empty_object_defaults( $ability->get_output_schema() ),
 			'meta'          => $ability->get_meta(),
 		);