[wp-trac] [WordPress Trac] #62003: User_Query cache triggers fatal error by ignoring 'fields' query var

[WordPress Trac]

#62003: User_Query cache triggers fatal error by ignoring 'fields' query var
--------------------------+-----------------------------
 Reporter:  sermitr       |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Users         |    Version:  6.6.1
 Severity:  normal        |   Keywords:
  Focuses:                |
--------------------------+-----------------------------
 Method `WP_User_Query::query()` generates different results depending on
 whether `$this->query_vars['fields']` an array (array of objects) or a
 string (array of scalar values).

 However, if it contains only one field, the generated SQL query will be
 the same.

 Function `generate_cache_key()` doesn't take into account the `fields`
 query var, and relies on the generated SQL query instead. This leads to
 the unpredictability of the returned data format (array of objects or
 array of scalar values).

 How to reproduce:
 1. Clean the cache: `wp cache flush`.
 2. Fetch the users passing `fields` as an array:
 {{{#!php
 <?php
 $wp_user_search = new WP_User_Query( array( 'fields' => array( 'ID' ),
 'count_total' => false ) );
 $users = $wp_user_search->get_results();
 var_dump( $users );
 // Result is an array of objects, which is now cached: array(1) { [0]=>
 object(stdClass)#1268 (2) { ["ID"]=> string(1) "1" ["id"]=> string(1) "1"
 } }
 }}}
 3. Run the same request with the `fields` being a string: `'fields' =>
 'ID'`. The result will be an array of objects pulled from cache, although
 array of strings is expected.
 3. Fetch the users by CLI command: `wp user list`. The result is expected
 to be an array of strings, so the fatal error is triggered:
 {{{
 Fatal error: Uncaught TypeError: Illegal offset type in wp-includes/class-
 wp-user-query.php:892
 }}}
 4. Clean the cache: `wp cache flush`
 5. Run the request from step 3, where `fields` is a string:
 {{{#!php
 <?php
 $wp_user_search = new WP_User_Query(array('fields' => 'ID', 'count_total'
 => false));
 $users = $wp_user_search->get_results();
 var_dump( $users);
 // Result is an array of strings, which is now cached: array(1) { [0]=>
 string(1) "1" }
 }}}
 6. Run the request from step 2, where `fields` is an array. The result be
 the same array of strings pulled from cache, which is different from what
 we had on step 2.
 7. Run the CLI command `wp user list`. There will be no fatal error,
 because the data pulled from cache is an array of strings as expected.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/62003>
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