[wp-trac] [WordPress Trac] #15157: Circular References in Categories

[WordPress Trac]

#15157: Circular References in Categories
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 Reporter:  interlock     |       Owner:                   
     Type:  defect (bug)  |      Status:  new              
 Priority:  normal        |   Milestone:  Awaiting Review  
Component:  Taxonomy      |     Version:  3.0.1            
 Severity:  normal        |    Keywords:  category taxonomy
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 Came across this with a client this morning.

 Basically, it appears that hierarchical taxonomy entries can end up in
 circular references quite easily, since the list only appears to filter
 out the current term entry, not any possible children entries as well. The
 first symptom of this is that the taxonomy entries disappear from the menu
 once this occurs. Requiring you to manually edit the database and fix the
 parent references. Some plugins also have a very difficult time dealing
 with this, leading to unpredictable behaviours and possibly some data
 corruption.

 Reproducing is easy!
 1. Make a category, let's say "Newsletters"
 2. Make a sub category, let's say "Newsletters Archive". Let's set the
 parent to "Newsletters"
 3. Let's go back and edit "Newsletters" and set the parent to "Newsletters
 Archive". (You ask yourself why you do this, but silently ignore the
 voice...)

 Results:
 Your category list no longer contains either entry now.

 Expected Result:
 Changing "Newletters" parent to "Newletters Archive" should result in a
 failure to save with a message about, "You cannot set the parent to a
 child of its self."

 Fix:
 Filter the parent selection when editing taxonomy entries to not include
 any children of the current entry. Should prevent most instances of this
 happening.

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Ticket URL: <http://core.trac.wordpress.org/ticket/15157>
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