[wp-trac] [WordPress Trac] #33187: Menu becomes empty after saving in WordPress 4.2.3

[WordPress Trac]

#33187: Menu becomes empty after saving in WordPress 4.2.3
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 Reporter:  jcexygy         |      Owner:
     Type:  defect (bug)    |     Status:  new
 Priority:  normal          |  Milestone:  Awaiting Review
Component:  Taxonomy        |    Version:  4.2.3
 Severity:  normal          |   Keywords:
  Focuses:  administration  |
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 After upgrading to WordPress 4.2.2 (and the same happens with 4.2.3), I
 tried to add an item to a menu (in Appearance > Menus), and upon clicking
 Save, the menu becomes blank.

 This bug seems to be related to the new Taxonomy Term Splitting
 functionality. The last commenter here seems to have had the same issue:
 https://make.wordpress.org/core/2015/02/16/taxonomy-term-splitting-
 in-4-2-a-developer-guide

 When this happened, I checked the database to see what was happening. It
 appears a new term was created in the wp_terms table. The original term
 was 'Apps' and had a term_id of 6. There was also a category using the
 term 'Apps'. I also checked the wp_term_relationships table, and all of
 the rows with a term_taxonomy_id of 6 have been deleted.

 I did a diff against the previous version of the database in order to find
 out what happened - here's a screenshot of part of that diff:
 https://www.dropbox.com/s/u76zynmz4jz5scx/Screenshot%202015-07-29%2014.43.16.png?dl=0

 Also, in the wp_term_taxonomy table, the related row changed - you can see
 by this diff that the term_id changed to 199 (which is the term_id of the
 newly created 'Apps' term), and the count went from 66 to 0:
 https://www.dropbox.com/s/oejbedp5vgur240/Screenshot%202015-07-29%2014.45.56.png?dl=0

 I've been able to replicate this several times on a dev site and live
 site. I deactivated all plugins and switched to the TwentyFourteen theme,
 and the issue still occurs. Note that once the "split" happens, I can add
 items back to the menu, and the problem doesn't recur. In order to
 replicate, I had to revert to a previous version of the database.

 I realize this is an edge case (having a menu name that's the same as a
 category name - or other taxonomy term), and that once it happens, the
 problem doesn't recur, but it can be frustrating and disconcerting to lose
 an entire menu structure, especially when that menu contains a lot of
 items and has to be re-created.

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Ticket URL: <https://core.trac.wordpress.org/ticket/33187>
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