Add filter(s) to get_adjacent_post function to change variables further down

[briandichiara]

I'm finding it incredibly difficult to sort a post type using the existing filters to order by custom post meta alphabetically on a single post (for next/previous post).

A use case is when I have a separate field for a custom post type called "Last Name" where I would want my posts to display in alphabetical order by last name. When sorting on an archive with pre_get_posts, it's not a problem, however when navigating posts from the single post, there just doesn't appear to be a simple way to change the "next" and "previous" posts to maintain the same custom sort order when dealing with an alphabetical meta_value.

I'm proposing adding one or two filters to the get_adjacent_post() function which allows the final query to be filtered, or more importantly, the query result to be filtered so a custom sort can be implemented.

[briandichiara]

patch to link-template.php to add 2 new filters

[swissspidy]

Hey Brian

The use case sounds reasonable. Two notes on the patch:

1. The filters need appropriate documentation, see for more information
2. Since $join, $where and $sort are used in the query string, these variables should probably passed to the filter callback as well.