Abilities API: Introduce server-side registry and REST API endpoints

Feature proposal at https://make.wordpress.org/ai/2025/07/17/abilities-api/.
Project developed in https://github.com/WordPress/abilities-api.

Introduces a new Abilities API that allows WordPress plugins and themes to register and execute custom abilities with built-in permission checking, input/output validation via JSON Schema, and REST API integration.

## Public Functions

### Ability Management
- `wp_register_ability( string $name, array $args ): ?WP_Ability` - Registers a new ability (must be called on `wp_abilities_api_init` hook)
- `wp_unregister_ability( string $name ): ?WP_Ability` - Unregisters an ability
- `wp_has_ability( string $name ): bool` - Checks if an ability is registered
- `wp_get_ability( string $name ): ?WP_Ability` - Retrieves a registered ability
- `wp_get_abilities(): array` - Retrieves all registered abilities

### Ability Category Management
- `wp_register_ability_category( string $slug, array $args ): ?WP_Ability_Category` - Registers an ability category (must be called on `wp_abilities_api_categories_init` hook)
- `wp_unregister_ability_category( string $slug ): ?WP_Ability_Category` - Unregisters an ability category
- `wp_has_ability_category( string $slug ): bool` - Checks if an ability category is registered
- `wp_get_ability_category( string $slug ): ?WP_Ability_Category` - Retrieves a registered ability category
- `wp_get_ability_categories(): array` - Retrieves all registered ability categories

## Public Classes

- `WP_Ability` - Encapsulates ability properties and methods (execute, check_permission, validate_input, etc.)
- `WP_Ability_Category` - Encapsulates ability category properties
- `WP_Abilities_Registry` - Manages ability registration and lookup (private, accessed via functions)
- `WP_Ability_Categories_Registry` - Manages ability category registration (private, accessed via functions)
- `WP_REST_Abilities_V1_List_Controller` - REST controller for listing abilities
- `WP_REST_Abilities_V1_Run_Controller` - REST controller for executing abilities

## REST API Endpoints

### Namespace: `wp-abilities/v1`

#### List Abilities
- `GET /wp-abilities/v1/abilities` - Retrieve all registered abilities
  - Query parameters: `page`, `per_page`, `category`

#### Get Single Ability
- `GET /wp-abilities/v1/abilities/(?P<name>[a-zA-Z0-9\-\/]+)` - Retrieve a specific ability by name

#### Execute Ability
- `GET|POST|DELETE /wp-abilities/v1/abilities/(?P<name>[a-zA-Z0-9\-\/]+)/run` - Execute an ability
  - Supports multiple HTTP methods based on ability annotations
  - Validates input against ability's input schema
  - Validates output against ability's output schema
  - Performs permission checks via ability's permission callback

## Hooks

### Actions
- `wp_abilities_api_categories_init` - Fired when ability categories registry is initialized (register categories here)
- `wp_abilities_api_init` - Fired when abilities registry is initialized (register abilities here)
- `wp_before_execute_ability` - Fired before an ability gets executed, after input validation and permissions check

- `wp_after_execute_ability` - Fires immediately after an ability finished executing

### Filters
- `wp_register_ability_category_args` - Filters ability category arguments before registration
- `wp_register_ability_args` - Filters ability arguments before registration

Developed in WordPress/wordpress-develop#9410.

Props gziolo, jorbin, justlevine, westonruter, jason_the_adams, flixos90, karmatosed, timothyblynjacobs.
Fixes #64098.



Built from https://develop.svn.wordpress.org/trunk@61032


git-svn-id: https://core.svn.wordpress.org/trunk@60368 1a063a9b-81f0-0310-95a4-ce76da25c4cd

Author: gziolo

wp-includes/abilities-api.php

@@ -0,0 +1,260 @@
+<?php
+/**
+ * Abilities API
+ *
+ * Defines functions for managing abilities in WordPress.
+ *
+ * @package WordPress
+ * @subpackage Abilities_API
+ * @since 6.9.0
+ */
+
+declare( strict_types = 1 );
+
+/**
+ * Registers a new ability using Abilities API.
+ *
+ * Note: Should only be used on the {@see 'wp_abilities_api_init'} hook.
+ *
+ * @since 6.9.0
+ *
+ * @see WP_Abilities_Registry::register()
+ *
+ * @param string               $name The name of the ability. The name must be a string containing a namespace
+ *                                   prefix, i.e. `my-plugin/my-ability`. It can only contain lowercase
+ *                                   alphanumeric characters, dashes and the forward slash.
+ * @param array<string, mixed> $args {
+ *     An associative array of arguments for the ability.
+ *
+ *     @type string               $label               The human-readable label for the ability.
+ *     @type string               $description         A detailed description of what the ability does.
+ *     @type string               $category            The ability category slug this ability belongs to.
+ *     @type callable             $execute_callback    A callback function to execute when the ability is invoked.
+ *                                                     Receives optional mixed input and returns mixed result or WP_Error.
+ *     @type callable             $permission_callback A callback function to check permissions before execution.
+ *                                                     Receives optional mixed input and returns bool or WP_Error.
+ *     @type array<string, mixed> $input_schema        Optional. JSON Schema definition for the ability's input.
+ *     @type array<string, mixed> $output_schema       Optional. JSON Schema definition for the ability's output.
+ *     @type array<string, mixed> $meta                  {
+ *         Optional. Additional metadata for the ability.
+ *
+ *         @type array<string, null|bool> $annotations  Optional. Annotation metadata for the ability.
+ *         @type bool                     $show_in_rest Optional. Whether to expose this ability in the REST API. Default false.
+ *     }
+ *     @type string               $ability_class       Optional. Custom class to instantiate instead of WP_Ability.
+ * }
+ * @return WP_Ability|null An instance of registered ability on success, null on failure.
+ */
+function wp_register_ability( string $name, array $args ): ?WP_Ability {
+	if ( ! did_action( 'wp_abilities_api_init' ) ) {
+		_doing_it_wrong(
+			__FUNCTION__,
+			sprintf(
+				/* translators: 1: abilities_api_init, 2: string value of the ability name. */
+				esc_html__( 'Abilities must be registered on the %1$s action. The ability %2$s was not registered.' ),
+				'<code>abilities_api_init</code>',
+				'<code>' . esc_html( $name ) . '</code>'
+			),
+			'6.9.0'
+		);
+		return null;
+	}
+
+	$registry = WP_Abilities_Registry::get_instance();
+	if ( null === $registry ) {
+		return null;
+	}
+
+	return $registry->register( $name, $args );
+}
+
+/**
+ * Unregisters an ability from the Abilities API.
+ *
+ * @since 6.9.0
+ *
+ * @see WP_Abilities_Registry::unregister()
+ *
+ * @param string $name The name of the registered ability, with its namespace.
+ * @return WP_Ability|null The unregistered ability instance on success, null on failure.
+ */
+function wp_unregister_ability( string $name ): ?WP_Ability {
+	$registry = WP_Abilities_Registry::get_instance();
+	if ( null === $registry ) {
+		return null;
+	}
+
+	return $registry->unregister( $name );
+}
+
+/**
+ * Checks if an ability is registered.
+ *
+ * @since 6.9.0
+ *
+ * @see WP_Abilities_Registry::is_registered()
+ *
+ * @param string $name The name of the registered ability, with its namespace.
+ * @return bool True if the ability is registered, false otherwise.
+ */
+function wp_has_ability( string $name ): bool {
+	$registry = WP_Abilities_Registry::get_instance();
+	if ( null === $registry ) {
+		return false;
+	}
+
+	return $registry->is_registered( $name );
+}
+
+/**
+ * Retrieves a registered ability using Abilities API.
+ *
+ * @since 6.9.0
+ *
+ * @see WP_Abilities_Registry::get_registered()
+ *
+ * @param string $name The name of the registered ability, with its namespace.
+ * @return WP_Ability|null The registered ability instance, or null if it is not registered.
+ */
+function wp_get_ability( string $name ): ?WP_Ability {
+	$registry = WP_Abilities_Registry::get_instance();
+	if ( null === $registry ) {
+		return null;
+	}
+
+	return $registry->get_registered( $name );
+}
+
+/**
+ * Retrieves all registered abilities using Abilities API.
+ *
+ * @since 6.9.0
+ *
+ * @see WP_Abilities_Registry::get_all_registered()
+ *
+ * @return WP_Ability[] The array of registered abilities.
+ */
+function wp_get_abilities(): array {
+	$registry = WP_Abilities_Registry::get_instance();
+	if ( null === $registry ) {
+		return array();
+	}
+
+	return $registry->get_all_registered();
+}
+
+/**
+ * Registers a new ability category.
+ *
+ * @since 6.9.0
+ *
+ * @see WP_Ability_Categories_Registry::register()
+ *
+ * @param string               $slug The unique slug for the ability category. Must contain only lowercase
+ *                                   alphanumeric characters and dashes.
+ * @param array<string, mixed> $args {
+ *     An associative array of arguments for the ability category.
+ *
+ *     @type string               $label       The human-readable label for the ability category.
+ *     @type string               $description A description of the ability category.
+ *     @type array<string, mixed> $meta        Optional. Additional metadata for the ability category.
+ * }
+ * @return WP_Ability_Category|null The registered ability category instance on success, null on failure.
+ */
+function wp_register_ability_category( string $slug, array $args ): ?WP_Ability_Category {
+	if ( ! did_action( 'wp_abilities_api_categories_init' ) ) {
+		_doing_it_wrong(
+			__METHOD__,
+			sprintf(
+				/* translators: 1: abilities_api_categories_init, 2: ability category slug. */
+				__( 'Ability categories must be registered on the %1$s action. The ability category %2$s was not registered.' ),
+				'<code>wp_abilities_api_categories_init</code>',
+				'<code>' . esc_html( $slug ) . '</code>'
+			),
+			'6.9.0'
+		);
+		return null;
+	}
+
+	$registry = WP_Ability_Categories_Registry::get_instance();
+	if ( null === $registry ) {
+		return null;
+	}
+
+	return $registry->register( $slug, $args );
+}
+
+/**
+ * Unregisters an ability category.
+ *
+ * @since 6.9.0
+ *
+ * @see WP_Ability_Categories_Registry::unregister()
+ *
+ * @param string $slug The slug of the registered ability category.
+ * @return WP_Ability_Category|null The unregistered ability category instance on success, null on failure.
+ */
+function wp_unregister_ability_category( string $slug ): ?WP_Ability_Category {
+	$registry = WP_Ability_Categories_Registry::get_instance();
+	if ( null === $registry ) {
+		return null;
+	}
+
+	return $registry->unregister( $slug );
+}
+
+/**
+ * Checks if an ability category is registered.
+ *
+ * @since 6.9.0
+ *
+ * @see WP_Ability_Categories_Registry::is_registered()
+ *
+ * @param string $slug The slug of the ability category.
+ * @return bool True if the ability category is registered, false otherwise.
+ */
+function wp_has_ability_category( string $slug ): bool {
+	$registry = WP_Ability_Categories_Registry::get_instance();
+	if ( null === $registry ) {
+		return false;
+	}
+
+	return $registry->is_registered( $slug );
+}
+
+/**
+ * Retrieves a registered ability category.
+ *
+ * @since 6.9.0
+ *
+ * @see WP_Ability_Categories_Registry::get_registered()
+ *
+ * @param string $slug The slug of the registered ability category.
+ * @return WP_Ability_Category|null The registered ability category instance, or null if it is not registered.
+ */
+function wp_get_ability_category( string $slug ): ?WP_Ability_Category {
+	$registry = WP_Ability_Categories_Registry::get_instance();
+	if ( null === $registry ) {
+		return null;
+	}
+
+	return $registry->get_registered( $slug );
+}
+
+/**
+ * Retrieves all registered ability categories.
+ *
+ * @since 6.9.0
+ *
+ * @see WP_Ability_Categories_Registry::get_all_registered()
+ *
+ * @return WP_Ability_Category[] The array of registered ability categories.
+ */
+function wp_get_ability_categories(): array {
+	$registry = WP_Ability_Categories_Registry::get_instance();
+	if ( null === $registry ) {
+		return array();
+	}
+
+	return $registry->get_all_registered();
+}