Rewrite endpoints are lost if a custom category or tag base is defined

[sanchothefat]

Problem

So this little bug was winding me up for a while.

The standard approach according to the codex for adding rewrite endpoints is to call the add_rewrite_endpoint() function within the init hook. So far so good.

The problem occurs whenever WP_Rewrite::init() is called after the init hook. It resets the endpoints array and so when rewrite rules are subsequently generated through the options-permalink.php admin page the rewrite rules are unknown to the system and hence don't work.

WP_Rewrite::init() is called within WP_Rewrite::set_category_base(), WP_Rewrite::set_tag_base() and WP_Rewrite::set_permalink_structure().

In the latter it is only called if the permalink structure has changed so on first save of a change endpoints are lost. In the other 2 it is called every time if the slug doesn't match the default so rewrites are always lost.

Solutions:

1. add an action hook to the start of WP_Rewrite::rewrite_rules() where endpoints should be added
2. store the endpoints at the start of WP_Rewrite::init() and restore them at the end
3. don't reset them at all

I think solution 3 would make sense, the endpoints could be defaulted to an empty array and I can't see any reason to want to reset them anyway.

I've attached a simple patch that works (for me at least).

NB. this problem may also affect the $extra_rules and $non_wp_rules but I haven't tested that theory yet.

Patch for rewrite endpoints being wiped in certain situations

This one just caught me out and cost me two hours. Looking forward to seeing this patch added to core soon.