Unexpected 404 after selecting Parent Page in Page Attributes for hierarchical CPT

[bobbingwide]

• I've read and understood the contribution guidelines.
• I've searched for any related issues and avoided creating a duplicate issue.

Please give us a description of what happened.

When selecting a parent page in the Page Attributes panel for a hierarchical Custom Post Type, a jQuery initiated REST request is sent to the server resulting in a 404. I believe the request is using pages instead of the Custom Post Type name.

https://s.b/cwiccer/wp-json/wp/v2/pages/1413

In this example the selected hierarchical post's ID was 1413.

This request appears to be coming from jQuery and is being invoked by WordPress SEO.
The request is not performed when WordPress SEO is deactivated.

Please describe what you expected to happen and why.

• I don't expect a 404.
• If any request is to be performed I expect it to be for the selected CPT.

How can we reproduce this behavior?

1. Create a hierarchical Custom Post Type, e.g. hierarchical, which supports page-attributes.
2. Create a hierarchical post called H1.
3. Create a new hierarchical post called H1.1.
4. Open the inspector and view the Network tab.
5. In the Page Attributes panel choose H1 as the Parent Page.
6. See the XHR request being fired off, the 404 response, and messages in the console.

Technical info

• If relevant, which editor is affected (or editors):

• Classic Editor
• Gutenberg
• Classic Editor plugin

• Which browser is affected (or browsers):

• Chrome
• Firefox
• Safari
• Other

Used versions

• WordPress version: 5.5.1
• Yoast SEO version: 14.9
• Gutenberg: 9.0.0 - but problem occurs when activated or deactivated
• Gutenberg plugin version:
• Classic Editor plugin version:
• Relevant plugins in case of a bug:

• Tested with theme: TwentyTwenty

• I used my plugin called oik-types to create the hierarchical CPT used for this test.
• I did not set any values for rest_base or rewrite.
• The problem does not occur for Pages.
• I initially discovered the problem for a different CPT. See Add support for block variations bobbingwide/oik-shortcodes#80

[Djennez]

Was able to reproduce. Looking at where / why this happens, it doesn't seem to affect much in terms of functionality.

For any developers looking to reproduce this, you can alter the Yoast Test Helper code (in src -> post-types.php) like this; replace private $movie_args with the following array (making it hierarchical):

		'label'        => 'Movies',
		'labels'       => [
			'name'          => 'Movies',
			'singular_name' => 'Movie',
			'add_new'       => 'Add New',
			'add_new_item'  => 'Add new movie',
		],
		'description'  => 'Our movies post type',
		'public'       => true,
		'menu_icon'    => 'dashicons-format-video',
		'has_archive'  => true,
		'hierarchical' => true,
		'rewrite'      => [
			'slug' => 'yoast-test-movies',
		],
		'show_in_rest' => true,
		'supports' => [
			'title', 'editor', 'author', 'thumbnail', 'page-attributes'
		],

Then, follow the reproduction steps as mentioned by @bobbingwide

[rmarcano]

Please inform the customer of conversation # 684024 when this conversation has been closed.

[mayada-ibrahim]

A user-provided workaround: https://limecanvas.com/how-to-set-a-page-as-the-parent-of-a-wordpress-custom-post-type/