Creating a wp_navigation in REST throws undefined property error in WordPress 6.5.

[Hug0-Drelon]

Description

Creating a wp_navigation in REST throws Undefined property: stdClass::$ID error.

Step-by-step reproduction instructions

Create a POST REST request on wp/v2/navigation with at least title or content parameter set.
See debug.log for an error such as:

Undefined property: stdClass::$ID

/var/www/html/wp-includes/blocks/navigation.php:1479
/var/www/html/wp-includes/class-wp-hook.php:326
/var/www/html/wp-includes/plugin.php:205
/var/www/html/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php:1399
/var/www/html/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php:650
/var/www/html/wp-includes/rest-api/class-wp-rest-server.php:1230
/var/www/html/wp-includes/rest-api/class-wp-rest-server.php:1063
/wordpress-phpunit/includes/spy-rest-server.php:71

Screenshots, screen recording, code snippet

Here is a PHPUnit test that shows the bug:

<?php

class Gutenberg_REST_Create_Navigation_Block_Test extends WP_UnitTestCase {
	public function test_block_core_navigation_rest_creation() {
		wp_set_current_user( 1 );

		$post_type_object = get_post_type_object( 'wp_navigation' );
		$request = new WP_REST_Request( 'POST', '/wp/v2/' . $post_type_object->rest_base );
		$request->set_param( 'title', 'Title ' . $post_type_object->label );
		$request->set_param( 'content', $post_type_object->label );
		$request->set_param( '_locale', 'user' );

		$response = rest_get_server()->dispatch( $request ); // Triggers the error.

                 // Assertions aren't reached.
		$this->assertNotEmpty( $response->get_status() );
		$this->assertSame( 201, $response->get_status() );
	}
}

For what I understand, the bug was introduced in this PR.
During creation, there is no $post->ID set yet, so doing get_post( $post->iD ) causes the error.

Environment info

• WordPress nightly (from 6.5 RC2 I think)

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[Mamaduka]

cc @ockham