`posts_selection` is an action, not a filter

[SeanDS]

The source code has the following filter registration:

add_filter( 'posts_selection', array( $this, 'fix_author_page' ) ); // use posts_selection since it's after WP_Query has built the request and before it's queried any posts

However, posts_selection is an action, not a filter, so this line presently does nothing.

[TheCrowned]

Thanks for reporting this, I will fix it. It will not change CAP behavior though, because the filter was firing anyway even if it technically is not a filter, as you said. You can see the function fix_author_page is being executed by dropping in a random print or exit.

tl;dr - when add_action() or add_filter() is called, a new WP_Hook object is generated. apply_filters() will fire the apply_filters() method of that object, while do_action() will fire the do_action() method of the object. However, this latter will in turn call the WP_Hook object apply_filters() method with an empty value to filter. Point is, the structure is the same, and the fact that fix_author_page() was not filtering anything but only changing global vars makes it work anyway.