[wp-trac] [WordPress Trac] #27123: get_categories returning duplicate child categories in 3.9

[WordPress Trac]

#27123: get_categories returning duplicate child categories in 3.9
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 Reporter:  BStofko                     |       Owner:
     Type:  defect (bug)                |      Status:  new
 Priority:  normal                      |   Milestone:  3.9
Component:  Taxonomy                    |     Version:  trunk
 Severity:  normal                      |  Resolution:
 Keywords:  needs-unit-tests has-patch  |     Focuses:
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Changes (by SergeyBiryukov):

 * keywords:  needs-patch needs-unit-tests => needs-unit-tests has-patch


Comment:

 So, we have a public function `get_term_children()`, which returns all
 child IDs of an item, and a private function `_get_term_children()`, which
 only returns child items (IDs or objects) from a given subset.

 It looks like the changes to `_get_term_children()` in [27108] and [27125]
 were an attempt to make it work like `get_term_children()`, i.e. return
 all child IDs, regardless of the passed subset. This leads to duplicated
 results when using `child_of`, due to the same items being added to the
 `$term_list` array twice.

 Instead, I think the correct fix for both #26903 and this ticket would be
 to revert those changes and just use `get_term_children()` in
 `get_terms()` when dealing with `hierarchical`.

 This is confirmed by unit tests, however they still intermittently fail
 for some unknown reason, as noted in IRC:
 http://irclogs.wordpress.org/chanlog.php?channel=wordpress-
 dev&day=2014-02-19&sort=asc#m794718

 [attachment:27123.patch] contains the fix and the new test. It also makes
 assertions for #26903 a bit more accurate.

 `delete_option()` hack looks weird, but it seems to be required for
 `get_terms()` to work properly in the test.
 `test_get_terms_exclude_tree()` has the same hack:
 [source:tags/3.8.1/tests/phpunit/tests/term/getTerms.php#L168] (added in
 [25933]).

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Ticket URL: <https://core.trac.wordpress.org/ticket/27123#comment:4>
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