Layout templates REST API (#43067)

* Endpoint shell

* Single layout template route

* Add area query arg

* Fix BlockTemplateRegistry::get_registered() return type

* Check if templates are registered before registering

* Use json format for layout templates response

* Remove unused use

* Use json format for layout templates response for get_items

* Consolidate processing for get_items and get_item

* LayoutTemplateRegistry

* Fix matching by id

* Get templates from LayoutTemplateRegistry

* Remove unused method

* Fix typo in code doc

* Move template instantiation to registry

* Return template instance, not json when instantiating

* Use LayoutTemplateRegistry instead of BlockTemplateRegistry

* Add code docs for rest controller

* Fix code doc in BlockTemplateRegistry

* Code docs for LayoutTemplateRegistry

* Changelog

* Add code doc for LayoutTemplatesServiceProvider

* Unit test for registering a layout template

* Unit tests for invalid params when registering layout template

* Unit test for layout template instantiation

* Unit test for instantiating layout templates with query params

* Unit test for layout template instance caching

* Cache layout template instances

* Refactor layout template info querying

* Add unit test for layout template instantiation actions

* Add before and after layout template instantiation actions

* Use layout template ID for array key

* REST API unit test to get all items

* Unit test for unregister_all

* Method to unregister all layout templates

* REST API unit test to get all items for a specific area

* Fix to_json() in TestLayoutTemplate

* REST API unit test to get single item

* Fix get_item

* REST API unit test for single item with invalid id

* REST API unit test for get all items for invalid area

* Fix test_cached_instances - array access

* Test that old register hook is called

* Call old register hook

* Remove before hook (will put in separate PR)

plugins/woocommerce/changelog/add-layout-templates-rest-api

@@ -0,0 +1,4 @@
+Significance: minor
+Type: add
+
+Template layout REST API endpoints.

plugins/woocommerce/includes/rest-api/Controllers/Version3/class-wc-rest-layout-templates-controller.php

@@ -0,0 +1,146 @@
+<?php
+/**
+ * REST API Layout Templates controller
+ *
+ * Handles requests to /layout-templates.
+ *
+ * @package WooCommerce\RestApi
+ * @since 8.6.0
+ */
+
+defined( 'ABSPATH' ) || exit;
+
+use Automattic\WooCommerce\LayoutTemplates\LayoutTemplateRegistry;
+
+/**
+ * REST API Layout Templates controller class.
+ */
+class WC_REST_Layout_Templates_Controller extends WC_REST_Controller {
+
+	/**
+	 * Endpoint namespace.
+	 *
+	 * @var string
+	 */
+	protected $namespace = 'wc/v3';
+
+	/**
+	 * Route base.
+	 *
+	 * @var string
+	 */
+	protected $rest_base = 'layout-templates';
+
+	/**
+	 * Register the routes for template layouts.
+	 */
+	public function register_routes() {
+		register_rest_route(
+			$this->namespace,
+			'/' . $this->rest_base,
+			array(
+				'methods'             => WP_REST_Server::READABLE,
+				'callback'            => array( $this, 'get_items' ),
+				'permission_callback' => array( $this, 'get_items_permissions_check' ),
+				'args'                => array(
+					'area' => array(
+						'description' => __( 'Area to get templates for.', 'woocommerce' ),
+						'type'        => 'string',
+						'default'     => '',
+					),
+				),
+			)
+		);
+
+		register_rest_route(
+			$this->namespace,
+			'/' . $this->rest_base . '/(?P<id>\w[\w\s\-]*)',
+			array(
+				'args' => array(
+					'id' => array(
+						'description' => __( 'Unique identifier for the resource.', 'woocommerce' ),
+						'type'        => 'string',
+					),
+				),
+				array(
+					'methods'             => WP_REST_Server::READABLE,
+					'callback'            => array( $this, 'get_item' ),
+					'permission_callback' => array( $this, 'get_item_permissions_check' ),
+					'args'                => array(),
+				),
+			)
+		);
+	}
+
+	/**
+	 * Check if a given request has access to read template layouts.
+	 *
+	 * @param WP_REST_Request $request The request.
+	 */
+	public function get_items_permissions_check( $request ): bool {
+		return true;
+	}
+
+	/**
+	 * Check if a given request has access to read a template layout.
+	 *
+	 * @param WP_REST_Request $request The request.
+	 */
+	public function get_item_permissions_check( $request ): bool {
+		return true;
+	}
+
+	/**
+	 * Handle request for template layouts.
+	 *
+	 * @param WP_REST_Request $request The request.
+	 */
+	public function get_items( $request ) {
+		$layout_templates = $this->get_layout_templates(
+			array(
+				'area' => $request['area'],
+			)
+		);
+
+		$response = rest_ensure_response( $layout_templates );
+
+		return $response;
+	}
+
+	/**
+	 * Handle request for a single template layout.
+	 *
+	 * @param WP_REST_Request $request The request.
+	 */
+	public function get_item( $request ) {
+		$layout_templates = $this->get_layout_templates(
+			array(
+				'id' => $request['id'],
+			)
+		);
+
+		if ( count( $layout_templates ) !== 1 ) {
+			return new WP_Error( 'woocommerce_rest_layout_template_invalid_id', __( 'Invalid layout template ID.', 'woocommerce' ), array( 'status' => 404 ) );
+		}
+
+		$response = rest_ensure_response( current( $layout_templates ) );
+
+		return $response;
+	}
+
+	/**
+	 * Get layout templates.
+	 *
+	 * @param array $query_params Query params.
+	 */
+	private function get_layout_templates( array $query_params ): array {
+		$layout_template_registry = wc_get_container()->get( LayoutTemplateRegistry::class );
+
+		return array_map(
+			function( $layout_template ) {
+				return $layout_template->to_json();
+			},
+			$layout_template_registry->instantiate_layout_templates( $query_params )
+		);
+	}
+}

plugins/woocommerce/includes/rest-api/Server.php

@@ -143,6 +143,7 @@ class Server {
 			'coupons'                  => 'WC_REST_Coupons_Controller',
 			'customer-downloads'       => 'WC_REST_Customer_Downloads_Controller',
 			'customers'                => 'WC_REST_Customers_Controller',
+			'layout-templates'         => 'WC_REST_Layout_Templates_Controller',
 			'network-orders'           => 'WC_REST_Network_Orders_Controller',
 			'order-notes'              => 'WC_REST_Order_Notes_Controller',
 			'order-refunds'            => 'WC_REST_Order_Refunds_Controller',

plugins/woocommerce/src/Admin/Features/ProductBlockEditor/Init.php

@@ -6,13 +6,14 @@
 namespace Automattic\WooCommerce\Admin\Features\ProductBlockEditor;
 
 use Automattic\WooCommerce\Admin\Features\Features;
-use Automattic\WooCommerce\Internal\Admin\Features\ProductBlockEditor\ProductTemplates\SimpleProductTemplate;
-use Automattic\WooCommerce\Internal\Admin\Features\ProductBlockEditor\ProductTemplates\ProductVariationTemplate;
 use Automattic\WooCommerce\Admin\Features\ProductBlockEditor\ProductTemplate;
 use Automattic\WooCommerce\Admin\PageController;
-use Automattic\WooCommerce\Internal\Admin\BlockTemplateRegistry\BlockTemplateRegistry;
-use Automattic\WooCommerce\Internal\Admin\BlockTemplates\Block;
+use Automattic\WooCommerce\LayoutTemplates\LayoutTemplateRegistry;
+
 use Automattic\WooCommerce\Internal\Admin\BlockTemplates\BlockTemplateLogger;
+use Automattic\WooCommerce\Internal\Admin\Features\ProductBlockEditor\ProductTemplates\SimpleProductTemplate;
+use Automattic\WooCommerce\Internal\Admin\Features\ProductBlockEditor\ProductTemplates\ProductVariationTemplate;
+
 use WP_Block_Editor_Context;
 
 /**
@@ -68,6 +69,8 @@ class Init {
 
 			add_action( 'current_screen', array( $this, 'set_current_screen_to_block_editor_if_wc_admin' ) );
 
+			add_action( 'rest_api_init', array( $this, 'register_product_editor_templates' ) );
+
 			// Make sure the block registry is initialized so that core blocks are registered.
 			BlockRegistry::get_instance();
 
@@ -211,12 +214,12 @@ class Init {
 	 * Get the product editor settings.
 	 */
 	private function get_product_editor_settings() {
-		$layout_template_registry = wc_get_container()->get( BlockTemplateRegistry::class );
+		$layout_template_registry = wc_get_container()->get( LayoutTemplateRegistry::class );
 		$layout_template_logger   = BlockTemplateLogger::get_instance();
 
 		$editor_settings = array();
 
-		foreach ( $layout_template_registry->get_all_registered() as $layout_template ) {
+		foreach ( $layout_template_registry->instantiate_layout_templates() as $layout_template ) {
 			$editor_settings['layoutTemplates'][] = $layout_template->to_json();
 
 			$layout_template_logger->log_template_events_to_file( $layout_template->get_id() );
@@ -370,9 +373,23 @@ class Init {
 	/**
 	 * Register product editor templates.
 	 */
-	private function register_product_editor_templates() {
-		$template_registry = wc_get_container()->get( BlockTemplateRegistry::class );
-		$template_registry->register( new SimpleProductTemplate() );
-		$template_registry->register( new ProductVariationTemplate() );
+	public function register_product_editor_templates() {
+		$layout_template_registry = wc_get_container()->get( LayoutTemplateRegistry::class );
+
+		if ( ! $layout_template_registry->is_registered( 'simple-product' ) ) {
+			$layout_template_registry->register(
+				'simple-product',
+				'product-form',
+				SimpleProductTemplate::class
+			);
+		}
+
+		if ( ! $layout_template_registry->is_registered( 'product-variation' ) ) {
+			$layout_template_registry->register(
+				'product-variation',
+				'product-form',
+				ProductVariationTemplate::class
+			);
+		}
 	}
 }

plugins/woocommerce/src/Container.php

@@ -30,6 +30,7 @@ use Automattic\WooCommerce\Internal\DependencyManagement\ServiceProviders\Restoc
 use Automattic\WooCommerce\Internal\DependencyManagement\ServiceProviders\UtilsClassesServiceProvider;
 use Automattic\WooCommerce\Internal\DependencyManagement\ServiceProviders\BatchProcessingServiceProvider;
 use Automattic\WooCommerce\Internal\DependencyManagement\ServiceProviders\BlockTemplatesServiceProvider;
+use Automattic\WooCommerce\Internal\DependencyManagement\ServiceProviders\LayoutTemplatesServiceProvider;
 
 /**
  * PSR11 compliant dependency injection container for WooCommerce.
@@ -77,6 +78,7 @@ final class Container {
 		MarketingServiceProvider::class,
 		MarketplaceServiceProvider::class,
 		BlockTemplatesServiceProvider::class,
+		LayoutTemplatesServiceProvider::class,
 		LoggingServiceProvider::class,
 		EnginesServiceProvider::class,
 	);

plugins/woocommerce/src/Internal/DependencyManagement/ServiceProviders/LayoutTemplatesServiceProvider.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace Automattic\WooCommerce\Internal\DependencyManagement\ServiceProviders;
+
+use Automattic\WooCommerce\Internal\DependencyManagement\AbstractServiceProvider;
+use Automattic\WooCommerce\LayoutTemplates\LayoutTemplateRegistry;
+
+/**
+ * Service provider for layout templates.
+ */
+class LayoutTemplatesServiceProvider extends AbstractServiceProvider {
+
+	/**
+	 * The classes/interfaces that are serviced by this service provider.
+	 *
+	 * @var array
+	 */
+	protected $provides = array(
+		LayoutTemplateRegistry::class,
+	);
+
+	/**
+	 * Register the classes.
+	 */
+	public function register() {
+		$this->share( LayoutTemplateRegistry::class );
+	}
+}

plugins/woocommerce/src/LayoutTemplates/LayoutTemplateRegistry.php

@@ -0,0 +1,190 @@
+<?php
+
+namespace Automattic\WooCommerce\LayoutTemplates;
+
+use Automattic\WooCommerce\Admin\BlockTemplates\BlockTemplateInterface;
+
+/**
+ * Layout template registry.
+ */
+final class LayoutTemplateRegistry {
+
+	/**
+	 * Class instance.
+	 *
+	 * @var LayoutTemplateRegistry|null
+	 */
+	private static $instance = null;
+
+	/**
+	 * Layout templates info.
+	 *
+	 * @var array
+	 */
+	protected $layout_templates_info = array();
+
+	/**
+	 * Layout template instances.
+	 *
+	 * @var array
+	 */
+	protected $layout_template_instances = array();
+
+	/**
+	 * Get the instance of the class.
+	 */
+	public static function get_instance(): LayoutTemplateRegistry {
+		if ( null === self::$instance ) {
+			self::$instance = new self();
+		}
+
+		return self::$instance;
+	}
+
+	/**
+	 * Unregister all layout templates.
+	 */
+	public function unregister_all() {
+		$this->layout_templates_info     = array();
+		$this->layout_template_instances = array();
+	}
+
+	/**
+	 * Check if a layout template is registered.
+	 *
+	 * @param string $layout_template_id Layout template ID.
+	 */
+	public function is_registered( $layout_template_id ): bool {
+		return isset( $this->layout_templates_info[ $layout_template_id ] );
+	}
+
+	/**
+	 * Register a single layout template.
+	 *
+	 * @param string $layout_template_id         Layout template ID.
+	 * @param string $layout_template_area       Layout template area.
+	 * @param string $layout_template_class_name Layout template class to register.
+	 *
+	 * @throws \ValueError If a layout template with the same ID already exists.
+	 * @throws \ValueError If the specified layout template area is empty.
+	 * @throws \ValueError If the specified layout template class does not exist.
+	 * @throws \ValueError If the specified layout template class does not implement the BlockTemplateInterface.
+	 */
+	public function register( $layout_template_id, $layout_template_area, $layout_template_class_name ) {
+		if ( $this->is_registered( $layout_template_id ) ) {
+			throw new \ValueError( 'A layout template with the specified ID already exists in the registry.' );
+		}
+
+		if ( empty( $layout_template_area ) ) {
+			throw new \ValueError( 'The specified layout template area is empty.' );
+		}
+
+		if ( ! class_exists( $layout_template_class_name ) ) {
+			throw new \ValueError( 'The specified layout template class does not exist.' );
+		}
+
+		if ( ! is_subclass_of( $layout_template_class_name, BlockTemplateInterface::class ) ) {
+			throw new \ValueError( 'The specified layout template class does not implement the BlockTemplateInterface.' );
+		}
+
+		$this->layout_templates_info[ $layout_template_id ] = array(
+			'id'         => $layout_template_id,
+			'area'       => $layout_template_area,
+			'class_name' => $layout_template_class_name,
+		);
+	}
+
+	/**
+	 * Instantiate the matching layout templates and return them.
+	 *
+	 * @param array $query_params Query params.
+	 */
+	public function instantiate_layout_templates( array $query_params = array() ): array {
+		$layout_templates = array();
+
+		$layout_templates_info = $this->get_matching_layout_templates_info( $query_params );
+		foreach ( $layout_templates_info as $layout_template_info ) {
+			$layout_template = $this->get_layout_template_instance( $layout_template_info );
+
+			$layout_templates[ $layout_template->get_id() ] = $layout_template;
+		}
+
+		return $layout_templates;
+	}
+
+	/**
+	 * Instantiate a single layout template and return it.
+	 *
+	 * @param array $layout_template_info Layout template info.
+	 */
+	private function get_layout_template_instance( $layout_template_info ): BlockTemplateInterface {
+		$class_name = $layout_template_info['class_name'];
+
+		// Return the instance if it already exists.
+
+		$layout_template_instance = isset( $this->layout_template_instances[ $class_name ] )
+			? $this->layout_template_instances[ $class_name ]
+			: null;
+
+		if ( ! empty( $layout_template_instance ) ) {
+			return $layout_template_instance;
+		}
+
+		// Instantiate the layout template.
+
+		$layout_template_instance                       = new $class_name();
+		$this->layout_template_instances[ $class_name ] = $layout_template_instance;
+
+		// Call the after instantiation hooks.
+
+		/**
+		 * Fires after a layout template is instantiated.
+		 *
+		 * @param string $layout_template_id Layout template ID.
+		 * @param string $layout_template_area Layout template area.
+		 * @param BlockTemplateInterface $layout_template Layout template instance.
+		 *
+		 * @since 8.6.0
+		 */
+		do_action( 'woocommerce_layout_template_after_instantiation', $layout_template_info['id'], $layout_template_info['area'], $layout_template_instance );
+
+		// Call the old, soon-to-be-deprecated, register hook.
+
+		/**
+		 * Fires when a template is registered.
+		 *
+		 * @param BlockTemplateInterface $template Template that was registered.
+		 *
+		 * @since 8.2.0
+		 */
+		do_action( 'woocommerce_block_template_register', $layout_template_instance );
+
+		return $layout_template_instance;
+	}
+
+	/**
+	 * Get matching layout templates info.
+	 *
+	 * @param array $query_params Query params.
+	 */
+	private function get_matching_layout_templates_info( array $query_params = array() ): array {
+		$area_to_match = isset( $query_params['area'] ) ? $query_params['area'] : null;
+		$id_to_match   = isset( $query_params['id'] ) ? $query_params['id'] : null;
+
+		$matching_layout_templates_info = array();
+
+		foreach ( $this->layout_templates_info as $layout_template_info ) {
+			if ( ! empty( $area_to_match ) && $layout_template_info['area'] !== $area_to_match ) {
+				continue;
+			}
+
+			if ( ! empty( $id_to_match ) && $layout_template_info['id'] !== $id_to_match ) {
+				continue;
+			}
+
+			$matching_layout_templates_info[] = $layout_template_info;
+		}
+
+		return $matching_layout_templates_info;
+	}
+}

plugins/woocommerce/tests/php/includes/rest-api/Controllers/Version3/class-wc-rest-layout-templates-controller-tests.php

@@ -0,0 +1,108 @@
+<?php
+
+use Automattic\WooCommerce\LayoutTemplates\LayoutTemplateRegistry;
+
+use Automattic\WooCommerce\Internal\Admin\Features\ProductBlockEditor\ProductTemplates\SimpleProductTemplate;
+use Automattic\WooCommerce\Internal\Admin\Features\ProductBlockEditor\ProductTemplates\ProductVariationTemplate;
+
+use Automattic\WooCommerce\Tests\LayoutTemplates\TestLayoutTemplate;
+
+/**
+ * class WC_REST_Layout_Templates_Controller_Tests.
+ * Layout Templates Controller tests for V3 REST API.
+ */
+class WC_REST_Layout_Templates_Controller_Tests extends WC_REST_Unit_Test_Case {
+	/**
+	 * Runs before each test.
+	 */
+	public function setUp(): void {
+		parent::setUp();
+
+		$layout_template_registry = wc_get_container()->get( LayoutTemplateRegistry::class );
+
+		$layout_template_registry->unregister_all();
+
+		$layout_template_registry->register( 'test-layout-template', 'test', TestLayoutTemplate::class );
+		$layout_template_registry->register( 'simple-product', 'product-form', SimpleProductTemplate::class );
+		$layout_template_registry->register( 'product-variation', 'product-form', ProductVariationTemplate::class );
+	}
+
+	/**
+	 * Test getting all layout templates.
+	 */
+	public function test_get_all_items() {
+		$response = $this->do_rest_get_request( 'layout-templates' );
+
+		$this->assertEquals( 200, $response->get_status() );
+
+		$data = $response->get_data();
+
+		$this->assertNotEmpty( $data );
+
+		$this->assertCount( 3, $data );
+
+		$this->assertArrayHasKey( 'test-layout-template', $data );
+		$this->assertArrayHasKey( 'simple-product', $data );
+		$this->assertArrayHasKey( 'product-variation', $data );
+	}
+
+	/**
+	 * Test getting all layout templates for a specific area.
+	 */
+	public function test_get_all_items_for_area() {
+		$response = $this->do_rest_get_request( 'layout-templates', array( 'area' => 'product-form' ) );
+
+		$this->assertEquals( 200, $response->get_status() );
+
+		$data = $response->get_data();
+
+		$this->assertNotEmpty( $data );
+
+		$this->assertCount( 2, $data );
+
+		$this->assertArrayHasKey( 'simple-product', $data );
+		$this->assertArrayHasKey( 'product-variation', $data );
+	}
+
+	/**
+	 * Test getting all layout templates for an invalid area.
+	 */
+	public function test_get_all_items_for_invalid_area() {
+		$response = $this->do_rest_get_request( 'layout-templates', array( 'area' => 'invalid-area' ) );
+
+		$this->assertEquals( 200, $response->get_status() );
+
+		$data = $response->get_data();
+
+		$this->assertEmpty( $data );
+	}
+
+	/**
+	 * Test getting a single layout template.
+	 */
+	public function test_get_single_item() {
+		$response = $this->do_rest_get_request( 'layout-templates/test-layout-template' );
+
+		$this->assertEquals( 200, $response->get_status() );
+
+		$data = $response->get_data();
+
+		$this->assertNotEmpty( $data );
+
+		$this->assertEquals( 'test-layout-template', $data['id'] );
+		$this->assertEquals( 'test', $data['area'] );
+
+		$this->assertArrayHasKey( 'title', $data );
+		$this->assertArrayHasKey( 'description', $data );
+		$this->assertArrayHasKey( 'blockTemplates', $data );
+	}
+
+	/**
+	 * Test getting a single layout template with invalid id.
+	 */
+	public function test_get_single_item_with_invalid_id() {
+		$response = $this->do_rest_get_request( 'layout-templates/invalid-layout-template' );
+
+		$this->assertEquals( 404, $response->get_status() );
+	}
+}

plugins/woocommerce/tests/php/src/LayoutTemplates/LayoutTemplateRegistryTest.php

@@ -0,0 +1,240 @@
+<?php
+
+namespace Automattic\WooCommerce\Tests\LayoutTemplates;
+
+use Automattic\WooCommerce\LayoutTemplates\LayoutTemplateRegistry;
+
+use Automattic\WooCommerce\Internal\Admin\Features\ProductBlockEditor\ProductTemplates\SimpleProductTemplate;
+use Automattic\WooCommerce\Internal\Admin\Features\ProductBlockEditor\ProductTemplates\ProductVariationTemplate;
+
+use WC_Unit_Test_Case;
+
+/**
+ * Tests for the LayoutTemplateRegistry class.
+ */
+class LayoutTemplateRegistryTest extends WC_Unit_Test_Case {
+	/**
+	 * Layout template registry.
+	 *
+	 * @var LayoutTemplateRegistry
+	 */
+	protected $layout_template_registry;
+
+	/**
+	 * Layout templates to register.
+	 *
+	 * @var array
+	 */
+	protected $layout_templates_to_register;
+
+	/**
+	 * Runs before each test.
+	 */
+	public function setUp(): void {
+		$this->layout_template_registry = new LayoutTemplateRegistry();
+
+		$this->layout_templates_to_register = array(
+			'test-layout-template' => array(
+				'area'       => 'test',
+				'class_name' => TestLayoutTemplate::class,
+			),
+			'simple-product'       => array(
+				'area'       => 'product-form',
+				'class_name' => SimpleProductTemplate::class,
+			),
+			'product-variation'    => array(
+				'area'       => 'product-form',
+				'class_name' => ProductVariationTemplate::class,
+			),
+		);
+	}
+
+	/**
+	 * Test registering a layout template.
+	 */
+	public function test_register() {
+		$this->assertFalse( $this->layout_template_registry->is_registered( 'test-layout-template' ) );
+
+		$this->layout_template_registry->register( 'test-layout-template', 'test', TestLayoutTemplate::class );
+
+		$this->assertTrue( $this->layout_template_registry->is_registered( 'test-layout-template' ) );
+	}
+
+	/**
+	 * Test registering a layout template with an existing ID.
+	 */
+	public function test_register_duplicate_id() {
+		$this->expectException( \ValueError::class );
+		$this->layout_template_registry->register( 'test-layout-template', 'test', TestLayoutTemplate::class );
+		$this->layout_template_registry->register( 'test-layout-template', 'test', TestLayoutTemplate::class );
+	}
+
+	/**
+	 * Test registering a layout template with an empty area.
+	 */
+	public function test_register_empty_area() {
+		$this->expectException( \ValueError::class );
+		$this->layout_template_registry->register( 'test-layout-template', '', TestLayoutTemplate::class );
+	}
+
+	/**
+	 * Test registering a layout template with a non-existing class.
+	 */
+	public function test_register_non_existing_class() {
+		$this->expectException( \ValueError::class );
+		$this->layout_template_registry->register( 'test-layout-template', 'test', 'NonExistingClass' );
+	}
+
+	/**
+	 * Test registering a layout template with a class that does not implement the BlockTemplateInterface.
+	 */
+	public function test_register_non_block_template_class() {
+		$this->expectException( \ValueError::class );
+		$this->layout_template_registry->register( 'test-layout-template', 'test', \stdClass::class );
+	}
+
+	/**
+	 * Test unregistering a layout template.
+	 */
+	public function test_unregister() {
+		$this->layout_template_registry->register( 'test-layout-template', 'test', TestLayoutTemplate::class );
+
+		$this->assertTrue( $this->layout_template_registry->is_registered( 'test-layout-template' ) );
+
+		$this->layout_template_registry->unregister_all( 'test-layout-template' );
+
+		$this->assertFalse( $this->layout_template_registry->is_registered( 'test-layout-template' ) );
+	}
+
+	/**
+	 * Test instantiating layout templates.
+	 */
+	public function test_instantiate() {
+		foreach ( $this->layout_templates_to_register as $template_id => $template_info ) {
+			$this->layout_template_registry->register( $template_id, $template_info['area'], $template_info['class_name'] );
+		}
+
+		$layout_templates = $this->layout_template_registry->instantiate_layout_templates();
+
+		$this->assertCount( 3, $layout_templates );
+
+		foreach ( $layout_templates as $layout_template ) {
+			$template_info = $this->layout_templates_to_register[ $layout_template->get_id() ];
+			$this->assertInstanceOf( $template_info['class_name'], $layout_template );
+		}
+	}
+
+	/**
+	 * Test instantiating layout templates with area query param.
+	 */
+	public function test_instantiate_with_area_query_param() {
+		foreach ( $this->layout_templates_to_register as $template_id => $template_info ) {
+			$this->layout_template_registry->register( $template_id, $template_info['area'], $template_info['class_name'] );
+		}
+
+		$layout_templates = $this->layout_template_registry->instantiate_layout_templates(
+			array( 'area' => 'product-form' )
+		);
+
+		$this->assertCount( 2, $layout_templates );
+
+		foreach ( $layout_templates as $layout_template ) {
+			$template_info = $this->layout_templates_to_register[ $layout_template->get_id() ];
+			$this->assertInstanceOf( $template_info['class_name'], $layout_template );
+		}
+	}
+
+	/**
+	 * Test instantiating layout templates with id query param.
+	 */
+	public function test_instantiate_with_id_query_param() {
+		foreach ( $this->layout_templates_to_register as $template_id => $template_info ) {
+			$this->layout_template_registry->register( $template_id, $template_info['area'], $template_info['class_name'] );
+		}
+
+		$layout_templates = $this->layout_template_registry->instantiate_layout_templates(
+			array( 'id' => 'simple-product' )
+		);
+
+		$this->assertCount( 1, $layout_templates );
+
+		foreach ( $layout_templates as $layout_template ) {
+			$template_info = $this->layout_templates_to_register[ $layout_template->get_id() ];
+			$this->assertInstanceOf( $template_info['class_name'], $layout_template );
+		}
+	}
+
+	/**
+	 * Test layout templates are only instantiated once.
+	 */
+	public function test_cached_instances() {
+		$this->layout_template_registry->register( 'test-layout-template', 'test', TestLayoutTemplate::class );
+
+		$layout_templates = $this->layout_template_registry->instantiate_layout_templates(
+			array( 'id' => 'test-layout-template' )
+		);
+
+		$layout_templates_again = $this->layout_template_registry->instantiate_layout_templates(
+			array( 'id' => 'test-layout-template' )
+		);
+
+		$this->assertCount( 1, $layout_templates );
+		$this->assertCount( 1, $layout_templates_again );
+
+		$this->assertSame( current( $layout_templates_again ), current( $layout_templates ) );
+	}
+
+	/**
+	 * Test layout template instantiation actions are fired.
+	 */
+	public function test_instantiation_actions() {
+		$after_instantiation_hook_called = false;
+
+		$after_instantiation_hook = function( string $layout_template_id, string $area, $layout_template ) use ( &$after_instantiation_hook_called ) {
+			$after_instantiation_hook_called = true;
+
+			$this->assertEquals( 'test-layout-template', $layout_template_id );
+			$this->assertEquals( 'test', $area );
+
+			$this->assertInstanceOf( TestLayoutTemplate::class, $layout_template );
+		};
+
+		$deprecated_register_hook_called = false;
+
+		$deprecated_register_hook = function( $layout_template ) use ( &$deprecated_register_hook_called ) {
+			$deprecated_register_hook_called = true;
+
+			$this->assertInstanceOf( TestLayoutTemplate::class, $layout_template );
+
+			$this->assertEquals( 'test-layout-template', $layout_template->get_id() );
+			$this->assertEquals( 'test', $layout_template->get_area() );
+
+		};
+
+		try {
+			add_action( 'woocommerce_layout_template_after_instantiation', $after_instantiation_hook, 10, 3 );
+
+			add_action( 'woocommerce_block_template_register', $deprecated_register_hook );
+
+			$this->layout_template_registry->register( 'test-layout-template', 'test', TestLayoutTemplate::class );
+
+			$this->layout_template_registry->instantiate_layout_templates(
+				array( 'id' => 'test-layout-template' )
+			);
+
+			$this->assertTrue(
+				$after_instantiation_hook_called,
+				'woocommerce_layout_template_after_instantiation hook was not called.'
+			);
+
+			$this->assertTrue(
+				$deprecated_register_hook_called,
+				'woocommerce_block_template_register hook was not called.'
+			);
+		} finally {
+			remove_action( 'woocommerce_layout_template_after_instantiation', $after_instantiation_hook );
+
+			remove_action( 'woocommerce_block_template_register', $deprecated_register_hook );
+		}
+	}
+}

plugins/woocommerce/tests/php/src/LayoutTemplates/TestLayoutTemplate.php

@@ -0,0 +1,98 @@
+<?php
+
+namespace Automattic\WooCommerce\Tests\LayoutTemplates;
+
+use Automattic\WooCommerce\Admin\BlockTemplates\BlockInterface;
+use Automattic\WooCommerce\Admin\BlockTemplates\BlockTemplateInterface;
+
+/**
+ * Test layout template.
+ */
+class TestLayoutTemplate implements BlockTemplateInterface {
+	/**
+	 * Get the layout template ID.
+	 */
+	public function get_id(): string {
+		return 'test-layout-template';
+	}
+
+	/**
+	 * Get the layout template title.
+	 */
+	public function get_title(): string {
+		return 'Test layout template';
+	}
+
+	/**
+	 * Get the layout template description.
+	 */
+	public function get_description(): string {
+		return 'A test layout template';
+	}
+
+	/**
+	 * Get the layout template area.
+	 */
+	public function get_area(): string {
+		return 'test';
+	}
+
+	/**
+	 * Get the layout template blocks.
+	 *
+	 * @param string $id_base Block ID base.
+	 */
+	public function generate_block_id( string $id_base ): string {
+		return $id_base . '-test';
+	}
+
+	/**
+	 * Get the layout template blocks.
+	 */
+	public function &get_root_template(): BlockTemplateInterface {
+		return $this;
+	}
+
+	/**
+	 * Get the layout template blocks.
+	 *
+	 * @param string $block_id Block ID.
+	 */
+	public function get_block( string $block_id ): ?BlockInterface {
+		return null;
+	}
+
+	/**
+	 * Get the layout template blocks.
+	 *
+	 * @param string $block_id Block ID.
+	 */
+	public function remove_block( string $block_id ) {
+	}
+
+	/**
+	 * Get the layout template blocks.
+	 */
+	public function remove_blocks() {
+	}
+
+	/**
+	 * Get the layout template blocks.
+	 */
+	public function get_formatted_template(): array {
+		return array();
+	}
+
+	/**
+	 * Get the layout template blocks.
+	 */
+	public function to_json(): array {
+		return array(
+			'id'             => $this->get_id(),
+			'title'          => $this->get_title(),
+			'description'    => $this->get_description(),
+			'area'           => $this->get_area(),
+			'blockTemplates' => array(),
+		);
+	}
+}