Custom Taxonomy filter on post listing pages

[jtsternberg]

Currently core adds a category dropdown filter to the admin post listing pages. I propose that there ought to be a parameter passed in to register_taxonomy similar to the show_admin_column (#21240) that would enable a filter dropdown for your custom taxonomy. Maybe 'taxononomy_filter' => true. I was sure a ticket would probably exist for this feature request, but was unable to find one.

[wonderboymusic]

28232.diff​ will get the dropdowns on the page. The query is built bizarrely, haven't figured it out yet.

[SergeyBiryukov]

__( 'View all ' ) . $other->labels->name is not localizable, see ticket:17609:3 and ticket:19099:1.

We can just use $other->labels->all_items (and also remove the "View" prefix from "View all categories"), which would be consistent with [27626].

[husobj]

Hi

I just discovered this ticket after working on a patch myself.
I will attach my patch 28232-alternate.diff for reference in case it's any use.

It's pretty similar although I have based my approach on the same way that 'show_admin_column' is implemented in terms of code structure.

I found that if I passed 'value_field' => 'slug' in wp_dropdown_categories() which was introduced in a recent-ish version of WP then the query just works as it queries the slug in the same way that the 'show_admin_column' terms links do.

[boonebgorges]

This seems like a good feature to me. A few comments on [28232-alternate.diff]:

• sprintf( __( 'Filter by %s' ), $taxonomy->labels->singular_name ) is not properly localizable, because of the way many languages will decline the taxonomy name. If we want the screen-reader-text to match that of the Category dropdown, then we'll need a new taxonomy label - something like 'filter_by_item'. @SergeyBiryukov does this seem right to you?
• We should pass 'hide_if_empty' => true to wp_dropdown_categories() - taxonomies with no terms should not have dropdowns here.
• Let's use booleans instead of integers when building the wp_dropdown_categories() argument array. (Never mind that the Category dropdown does it the other way.)
• Not all taxonomies will have a non-false query_var, and I don't think we need to depend on the existence of query_var to make this feature work. I recommend doing something like this: if the taxonomy has a non-boolean query_var, use it; otherwise use sanitize_title_with_dashes( $taxonomy->name )
• We need better escaping (esc_attr()) in the <label> element.
• Why bother getting the 'objects' from get_object_taxonomies() and filtering down to 'name' on the next line, only to call get_taxonomy() in the foreach loop? I'd suggest removing the fourth param ('name') in wp_filter_object_list().

[SergeyBiryukov]

Replying to boonebgorges:

sprintf( __( 'Filter by %s' ), $taxonomy->labels->singular_name ) is not properly localizable, because of the way many languages will decline the taxonomy name. If we want the screen-reader-text to match that of the Category dropdown, then we'll need a new taxonomy label - something like 'filter_by_item'. @SergeyBiryukov does this seem right to you?

Yes, either that or a workaround like __( 'Filter by taxonomy: %s' ).

[johnbillion]

I think this should be opt-in, either on a per-post-type or per-taxonomy basis. If a custom post type has more than about three custom taxonomies then the screen will get really cluttered.

[boonebgorges]

I think this should be opt-in

+1. I was imagining it being on a per-taxonomy basis, but I could imagine 'show_admin_filter' also accepting an array of post types.

[melchoyce]

If this is still relevant, can someone post screenshots for review?

[JoshuaWold]

UI exploration of this ticket

[JoshuaWold]

@wonderboymusic @husobj wanted to followup and see if this sketch is what you had in mind for how taxonomies would display in the post list page?

[runofthemill]

Saw this on Slack and shared with @JoshuaWold ​https://github.com/johnbillion/extended-cpts which provides the functionality (and more) covered by this ticket. Above are a couple of quick screens of how it looks in WP Admin!

[drzraf]

The query tweak needed is here: ​http://scribu.net/wordpress/sortable-taxonomy-columns.html

                $clauses['join'] .= <<<SQL
LEFT OUTER JOIN {$wpdb->term_relationships} ON {$wpdb->posts}.ID={$wpdb->term_relationships}.object_id
LEFT OUTER JOIN {$wpdb->term_taxonomy} USING (term_taxonomy_id)
LEFT OUTER JOIN {$wpdb->terms} USING (term_id)
SQL;
                $clauses['where'] .= " AND (taxonomy = 'color' OR taxonomy IS NULL)";
                $clauses['groupby'] = "object_id";
                $clauses['orderby']  = "GROUP_CONCAT({$wpdb->terms}.name ORDER BY name ASC) ";
                $clauses['orderby'] .= ( 'ASC' == strtoupper( $wp_query->get('order') ) ) ? 'ASC' : 'DESC';

What is needed is an easy and structured way to wrap and this kind of information to a WP_Query without messing-up with other existing query parameters.