[wp-trac] [WordPress Trac] #48360: `meta_value` is ignored when empty string is provided

[WordPress Trac]

#48360: `meta_value` is ignored when empty string is provided
--------------------------+-----------------------------
 Reporter:  JPry          |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Query         |    Version:  3.2
 Severity:  normal        |   Keywords:
  Focuses:                |
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 When trying to create a custom query using `meta_*` parameters,
 `WP_Meta_Query` will ignore `meta_value` if it is an empty string.

 This does appear to be somewhat intentional, since `WP_Query` will set the
 default value for `meta_value` to an empty string. This can be seen here:
 https://core.trac.wordpress.org/browser/trunk/src/wp-includes/class-wp-
 meta-query.php#L255

 The problem comes when you want to write a query that specifically targets
 meta keys that have empty values. The `'meta_value' => ''` parameter is
 stripped, and then the query does not behave properly. Here's an example
 query:

 {{{#!php
 <?php
 $args = array(
     'post_type'      => 'product',
     'posts_per_page' => 10,
     'meta_key'       => '_regular_price',
     'meta_value'     => '',
     'meta_compare'   => '=',
 );

 $query = new WP_Query( $args );
 }}}


 I would like to propose that an empty string be allowed for `meta_value`.
 Alternatively, the fact that an empty value will be stripped should at
 least be documented more clearly so that developers know to expect that
 behavior.

 Props also to richardbuff for helping identify the issue.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/48360>
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