WP_Query's "fields" => "ids" should return an array of integers

[danielbachhuber]

When using WP_Query's "fields" => "ids" (or "fields" => "id=>parent"), the returned values should be an array of integers, not array of integers represented by strings.

The current, latter behavior causes a subsequent WP_Query with post__in to fail because it's being passed an array of strings.

[danielbachhuber]

Cast returned post IDs as integers

[nacin]

I'm all for this but post__in appears to accept an array of numeric strings fine:

$post__in = implode(',', array_map( 'absint', $q['post__in'] ));

[wonderboymusic]

In 27686:

When using WP_Query's "fields" => "ids" (or "fields" => "id=>parent"), the returned values should be an array of integers, not array of integers represented by strings.

Adds unit tests. All other unit tests pass.

Props danielbachhuber.
Fixes #27252.

[SergeyBiryukov]

Follow-up: #31194

[SergeyBiryukov]

In 31324:

When using WP_Query's 'fields' => 'ids' (or 'fields' => 'id=>parent'), make sure the returned result is always an array of integers.

fixes #31194. see #27252.