Gutenberg doesn't show metaboxes for Tags & Categories, for custom post types

[nicolasleroy]

When enabling a custom post type for default taxonomies "category" and "post_tag", Gutenberg doesn't show the Tags & Categories metaboxes in the right-hand panel.

Steps to reproduce the behavior:

1. I have installed a fresh WordPress setup; using TwentyNineteen as theme.

2. In functions.php, I have created my post type using the following piece of code:

register_post_type('album', array(
			'public' => true,
			'show_ui' => true,
			'publicly_queryable' => true,
			'exclude_from_search' => false,
			'map_meta_cap' => true,
			'capability_type' => 'post',
			'hierarchical' => false,
			'query_var' => true,
			'supports' => array('title', 'editor', 'custom-fields', 'comments'),		
			'label' => __('Albums'),
			'singular_label' => __('Album'),
			'show_in_rest' => true,
			'taxonomies' => array('category', 'post_tag'),
			'rewrite' => array('slug' => 'album', 'with_front' => false )
		));

3. In WordPress Admin, I can create a new “album” without any problem, but don’t see the metabox to create tags (as I do see when creating a post)

4. On the page to create a new “album”, when checking “3 dots > Options”, I don’t see the option to display the “Tags” metabox.

5. When debugging, and doing “print_r($wp_taxonomies);”, I can see that my custom post type “album” is registered within the “[object_type]” array of “[post_tag] => WP_Taxonomy Object”

6. Issue reproduced on 3 different instances of Wordpress.

Expected behavior : I expect a metabox to manage Tags & Categories, to appear on the right-hand side, as I do have when managing posts.

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Microsoft Edge with Chromium
• Version: 80.0.361.9
• Wordpress 5.3.2, with embedded Gutenberg version.

PS: a support request has been created, but I have been advised to open a bug request instead - https://wordpress.org/support/topic/custom-post-types-gutenberg-tags-2-2/

[youknowriad]

I was not able to reproduce this personally as you can see in the screenshot (album CPT created with the exact same code as above)

[nicolasleroy]

Interesting. @youknowriad would you be able to tell me what Wordpress / Gutenberg versions you use? Thanks !

[youknowriad]

I'm using master (this is Gutenberg 7.2 approximatively) but I'm pretty sure we didn't touch this code for a long time now.

[nicolasleroy]

Thanks @youknowriad .

I have reinstalled a fresh Wordpress 5.3.2, with TwentyNineteen as theme. I have added Gutenberg 7.3 as plugin. I have added the CPT definition in functions.php (I've tried at the top of it, at the bottom of it).

And still don't see Tags or Categories metaboxes in the right-hand side column.

Really don't get what can be different between my setup and yours ... What mystery.

[youknowriad]

I think the issue is that you should run the CPT creation on the "init" hook and not at the root of the file. this should fix it.

[nicolasleroy]

@youknowriad THANK YOU SO MUCH !!! I had this problem opened for 8 months, was unable to put my head around this... And it was a matter of reading properly the documentation for register_post_type ...

Thank you very much again, as I wouldn't have solved this by myself.