fix(templates): nest the REST endpoint so 'schema' survives register_rest_route()'s upgrade step (C)

templates/src/Rest/Rest_Controller.php

@@ -44,23 +44,31 @@ public function init_hooks(): void {
 	 * @return void
 	 */
 	public function register_routes() {
+		// The endpoint definition is nested one level deeper than 'schema':
+		// register_rest_route() checks for a top-level 'callback' key and, if
+		// present, wraps the *whole* array as a single numerically-indexed
+		// endpoint -- 'schema' included, if it were a sibling of 'callback'
+		// here instead of one level up. Nesting keeps 'schema' a route-level
+		// option core can actually find.
 		register_rest_route(
 			$this->namespace,
 			'/' . $this->rest_base,
 			array(
-				'methods'             => \WP_REST_Server::READABLE,
-				'callback'            => $this->get_items( ... ),
-				'permission_callback' => $this->get_items_permissions_check( ... ),
-				'args'                => array(
-					'param' => array(
-						'required'          => false,
-						'sanitize_callback' => 'sanitize_text_field',
-						'validate_callback' => function ( $param ) {
-							return is_string( $param );
-						},
+				array(
+					'methods'             => \WP_REST_Server::READABLE,
+					'callback'            => $this->get_items( ... ),
+					'permission_callback' => $this->get_items_permissions_check( ... ),
+					'args'                => array(
+						'param' => array(
+							'required'          => false,
+							'sanitize_callback' => 'sanitize_text_field',
+							'validate_callback' => function ( $param ) {
+								return is_string( $param );
+							},
+						),
 					),
 				),
-				'schema'              => $this->get_public_item_schema( ... ),
+				'schema' => $this->get_public_item_schema( ... ),
 			)
 		);
 	}

templates/tests/Unit/Rest_Controller_Test.php

@@ -52,6 +52,29 @@ public function test_register_routes(): void {
 		$this->assertTrue( true );
 	}
 
+	/**
+	 * The schema must be a route-level option, not a key inside the endpoint
+	 * definition -- register_rest_route() only upgrades a flat array to
+	 * multiple endpoints when it sees a top-level 'callback' key, and
+	 * otherwise swallows 'schema' into that same numerically-indexed entry,
+	 * where core never looks for it (C).
+	 */
+	public function test_register_routes_exposes_schema_as_a_route_option(): void {
+		Functions\when( '__' )->returnArg();
+
+		Functions\expect( 'register_rest_route' )
+			->once()
+			->andReturnUsing(
+				function ( $route_namespace, $route, $args ) {
+					$this->assertArrayHasKey( 'schema', $args, 'schema must be a route option, not inside the endpoint' );
+					$this->assertArrayHasKey( 0, $args, 'the endpoint must be nested so core does not swallow schema' );
+					return true;
+				}
+			);
+
+		( new Rest_Controller() )->register_routes();
+	}
+
 	/**
 	 * The permission callback fails closed — it gates on a capability, it does
 	 * not blanket-allow.