WP Super Cache does not clear category and tag pages in some cases

[tigertech]

I have a WordPress installation using these settings:

permalink_structure: /posts/%postname%/
category_base: /category/
tag_base: <no value>

WP Super Cache doesn't clear the cached page for a matching tag when I publish a new post with that tag, although it does clear the categories.

I've traced the problem to the "wpsc_delete_cats_tags" function in wp-cache-phase2.php:

$tag_base = get_option( 'tag_base' );
if ( $tag_base == '' )
    $tag_base = '/tag/';

This isn't right: on my system, the correct path begins with "/posts/tag/". The difference means that wpsc_delete_cats_tags() doesn't find and delete the obsolete tag file.

In "wp-includes/rewrite.php", there's documentation for get_tag_permastruct() that says:

• If the tag_base property has no value, then the tag structure will have
• the front property value, followed by 'tag', and finally '%tag%'. If it
• does, then the root property will be used, along with the tag_base
• property value.

Note that it says it first begins with the "front property value" -- that is, the first part of the posts permalink ("/posts/" in my case). It's not necessarily just "/tag/".

(I think that documentation might be slightly wrong, because when I call get_tag_permastruct, what I get back ends in "%post_tag%", not "%tag%". But that's unrelated to the problem at hand.)

There's similar code for categories:

$category_base = get_option( 'category_base');
if ( $category_base == '' )
    $category_base = '/category/';

... but I wasn't affected by this because I have category_base set.

Perhaps these could be replaced with code that calls $wp_rewrite->get_tag_permastruct() and $wp_rewrite->get_category_permastruct), then does a str_replace to remove the trailing "%post_tag%" and "%category%"?