Add level class to terms list-table rows

[johnjamesjacoby]

I have a need to style & target taxonomy terms of a certain depth in the terms list table. Posts already includes a level-%d style class, so this should be pretty straight forward.

One caveat is that posts uses get_post_ancestors() (and terms will need to use get_ancestors()) but this comment from @nacin may not apply in exactly the same way.

There also is no get_term_class() function ala get_post_class(), so I'm going to propose a patch for only the single purpose of this ticket vs. aiming for feature parity with posts.

See #25791, r26244. Patch imminent.

[johnjamesjacoby]

For added context, I have this plugin: ​https://wordpress.org/plugins/wp-term-order/

As is, I cannot target terms within the same branch in the hierarchy, which results in the next/prev/current positions only being based on a flat term relationship. This means when terms are reordered, it reorders the entire view, not just siblings.

The attached patch would allow me to target .level-2, and I could query, rearrange, and redraw only the correct terms.

[boonebgorges]

This seems like a good and straightforward enhancement.

Performance issues were my only initiall concern. But seeing as this arises only on edit-tags.php, performance is less worrisome. Moreover, the way that edit-tags.php is built (top-of-hierarchy, down), the parents fetched by get_term( $term->parent ) should be in the cache in nearly all circumstances.

[boonebgorges]

In 44804:

Taxonomy: Add level-n classes to rows on edit-tags.php.

Props johnjamesjacoby.
Fixes #38810.