[wp-trac] [WordPress Trac] #33341: WP_Meta_Query IN operator with empty array does not return expected result

[WordPress Trac]

#33341: WP_Meta_Query IN operator with empty array does not return expected result
--------------------------+-----------------------------
 Reporter:  flixos90      |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Query         |    Version:  trunk
 Severity:  normal        |   Keywords:
  Focuses:                |
--------------------------+-----------------------------
 When using the `IN` compare mode in a `WP_Meta_Query` where the value is
 an empty array, this query is evaluated with an unexpected behavior.

 For example, I have some posts with a meta field called `'some-
 textfield'`:

 {{{
 $posts = get_posts( array(
         'posts_per_page' => -1,
         'post_type' => 'post',
         'post_status' => 'publish',
         'meta_query' => array(
                 array(
                         'key'    => 'some-textfield',
                         'value' => array(),
                         'compare' => 'IN',
                 ),
         ),
 ) );
 }}}

 This code returns all posts although I would rather expect it to return no
 posts at all since the value of `'some-textfield'` (whatever it may be) is
 not ''in'' those provided in the `value` field.

 I discovered it when I needed to perform a meta query where the value was
 an array that was returned by a previous operation. It is obviously a
 minor issue since we can simply check if the array is empty (and in that
 case do not make the query at all) - but I thought it's not really the
 expected result of such a query.

 The solution would be to:
 * ignore this condition if the `relation` is set to `OR` and there are
 other conditions available
 * evaluate this condition to false otherwise (and thus return no results)

--
Ticket URL: <https://core.trac.wordpress.org/ticket/33341>
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