Code Styling Project

While writing new posts you will realize, that something is wrong with the tree view of all categories. WordPress lists all categories as tree and i expect that the defined tree structure will be shown all the time.

Unfortunately WordPress steps in with an unexpected manner which forces the tree view to be shown damaged. The sorting of already used categories for the actual post in front of tree breaks the tree view and makes a tree view obsolete.

Again i was searching the code lines at WordPress Core, that are responsible for this damaged display. Finally i found it at the file template.php inside the function wp_category_checklist. The function tries a pre-filter on categories, which already have been used for this post. This results into creation of 2 disjuct sets of categories:

• categories already assigned to this post
• all unassigned remaining categories

Afterwards both sets will be dumped as HTML tree views. Because of this rupture of tree connections only a part of the categories can be shown as tree view. All not found parent relations will result into appending the categories in linear order at the end of possible tree. The above shown image may illustrate this issue in a simple way.

The only solution i found is a modification of WordPress Core. That’s why i changed the file: wp-admin/includes/template.php at function wp_category_checklist and have commented out the pre-filtering:

The red marked section is the pre-filter not longer been executed but keeped for the moment at file. But i was also curious to know, what other WordPress versions have a similar coding to this. After inspectation of all versions beginning 2.7-RC1 downto 2.5.1 i realized, that this code can be found unchanged at all of them. So the patch can be applied to all this versions as shown here.

As you can see the result is a logical tree view, that displays correctly the relationship of all categories as expected. This patch is a simple solution to solve this issue. In my opinion the WordPress core team has to find a more sophisticated solution. If categories will be shown as tree than all relations should be displayed in a way that meets the parent relationship defined at category page.

I will register this issue at WordPress Bug Trac and will try to explain it there. Hopefully an appropriated solution will be published at upcomming releases of WordPress, but i’m afraid, that it is too late for next version 2.7 published soon.

The issue has been filed at WordPress Trac as follows: Ticket #8521