Proposal: Add label argument to register_meta function

src/wp-includes/meta.php

@@ -1368,6 +1368,7 @@ function sanitize_meta( $meta_key, $meta_value, $object_type, $object_subtype =
  * @since 5.3.0 Valid meta types expanded to include "array" and "object".
  * @since 5.5.0 The `$default` argument was added to the arguments array.
  * @since 6.4.0 The `$revisions_enabled` argument was added to the arguments array.
+ * @since 6.7.0 The `label` argument was added to the arguments array.
  *
  * @param string       $object_type Type of object metadata is for. Accepts 'post', 'comment', 'term', 'user',
  *                                  or any other object type with an associated meta table.
@@ -1379,6 +1380,7 @@ function sanitize_meta( $meta_key, $meta_value, $object_type, $object_subtype =
  *                                         the meta key will be registered on the entire object type. Default empty.
  *     @type string     $type              The type of data associated with this meta key.
  *                                         Valid values are 'string', 'boolean', 'integer', 'number', 'array', and 'object'.
+ *     @type string     $label             A human-readable label of the data attached to this meta key.
  *     @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           The default value returned from get_metadata() if no value has been set yet.
@@ -1411,6 +1413,7 @@ function register_meta( $object_type, $meta_key, $args, $deprecated = null ) {
 	$defaults = array(
 		'object_subtype'    => '',
 		'type'              => 'string',
+		'label'             => '',
 		'description'       => '',
 		'default'           => '',
 		'single'            => false,

src/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php

@@ -478,6 +478,7 @@ protected function get_registered_fields() {
 
 			$default_schema = array(
 				'type'        => $default_args['type'],
+				'title'       => empty( $args['label'] ) ? '' : $args['label'],
 				'description' => empty( $args['description'] ) ? '' : $args['description'],
 				'default'     => isset( $args['default'] ) ? $args['default'] : null,
 			);

tests/phpunit/tests/meta/registerMeta.php

@@ -92,6 +92,7 @@ public function test_register_meta_with_post_object_type_populates_wp_meta_keys(
 				'' => array(
 					'flight_number' => array(
 						'type'              => 'string',
+						'label'             => '',
 						'description'       => '',
 						'single'            => false,
 						'sanitize_callback' => null,
@@ -117,6 +118,7 @@ public function test_register_meta_with_term_object_type_populates_wp_meta_keys(
 				'' => array(
 					'category_icon' => array(
 						'type'              => 'string',
+						'label'             => '',
 						'description'       => '',
 						'single'            => false,
 						'sanitize_callback' => null,
@@ -172,6 +174,7 @@ public function test_register_meta_with_current_sanitize_callback_populates_wp_m
 				'' => array(
 					'flight_number' => array(
 						'type'              => 'string',
+						'label'             => '',
 						'description'       => '',
 						'single'            => false,
 						'sanitize_callback' => array( $this, '_new_sanitize_meta_cb' ),
@@ -256,6 +259,19 @@ public function test_get_registered_meta_keys_with_invalid_type_is_empty() {
 		$this->assertEmpty( $meta_keys );
 	}
 
+	/**
+	 * @ticket 61998
+	 */
+	public function test_get_registered_meta_keys_label_arg() {
+		register_meta( 'post', 'registered_key1', array( 'label' => 'Field label' ) );
+
+		$meta_keys = get_registered_meta_keys( 'post' );
+
+		unregister_meta_key( 'post', 'registered_key1' );
+
+		$this->assertSame( 'Field label', $meta_keys['registered_key1']['label'] );
+	}
+
 	public function test_get_registered_meta_keys_description_arg() {
 		register_meta( 'post', 'registered_key1', array( 'description' => 'I\'m just a field, take a good look at me' ) );
 
@@ -340,6 +356,7 @@ public function test_register_meta_with_subtype_populates_wp_meta_keys( $type, $
 				$subtype => array(
 					'flight_number' => array(
 						'type'              => 'string',
+						'label'             => '',
 						'description'       => '',
 						'single'            => false,
 						'sanitize_callback' => null,
@@ -394,6 +411,7 @@ public function test_unregister_meta_without_subtype_keeps_subtype_meta_key( $ty
 				$subtype => array(
 					'flight_number' => array(
 						'type'              => 'string',
+						'label'             => '',
 						'description'       => '',
 						'single'            => false,
 						'sanitize_callback' => null,

tests/phpunit/tests/rest-api/rest-post-meta-fields.php

@@ -243,6 +243,18 @@ public function set_up() {
 			)
 		);
 
+		register_post_meta(
+			'post',
+			'with_label',
+			array(
+				'type'         => 'string',
+				'single'       => true,
+				'show_in_rest' => true,
+				'label'        => 'Meta Label',
+				'default'      => '',
+			)
+		);
+
 		/** @var WP_REST_Server $wp_rest_server */
 		global $wp_rest_server;
 		$wp_rest_server = new Spy_REST_Server();
@@ -3095,6 +3107,19 @@ public function test_default_is_added_to_schema() {
 		$this->assertSame( 'Goodnight Moon', $schema['default'] );
 	}
 
+	/**
+	 * @ticket 61998
+	 */
+	public function test_title_is_added_to_schema() {
+		$request  = new WP_REST_Request( 'OPTIONS', '/wp/v2/posts' );
+		$response = rest_do_request( $request );
+
+		$schema = $response->get_data()['schema']['properties']['meta']['properties']['with_label'];
+
+		$this->assertArrayHasKey( 'default', $schema );
+		$this->assertSame( 'Meta Label', $schema['title'] );
+	}
+
 	/**
 	 * Ensures that REST API calls with post meta containing the default value for the
 	 * registered meta field stores the default value into the database.

tests/phpunit/tests/user/wpRegisterPersistedPreferencesMeta.php

@@ -31,6 +31,7 @@ public function test_should_register_persisted_preferences_meta() {
 		$this->assertSame(
 			array(
 				'type'              => 'object',
+				'label'             => '',
 				'description'       => '',
 				'single'            => true,
 				'sanitize_callback' => null,