$query->post is null when WP_Query `fields` parameter is present

[wujek_bogdan]

Normally, WP_Query returns an object where $query->posts contains an array of posts and $query->post contains the first post. But if the fields parameter is present then $query->post returns null. Is it a bug or an expected behaviour? If it's expected then it should be documented because it's confusing and unintuitive.

Example:

<?php

// Works as expected
$query = new \WP_Query([
    'post_type' => 'my-post-type',
]);

if ($query->have_posts()) {
    $firstPost = $query->post; // returns the same as $query->$posts[0]
}

// Weird behaviour
$query = new \WP_Query([
    'post_type' => 'my-post-type',
    'fields'    => 'ids',
]);

if ($query->have_posts()) {
    $firstPost = $query->post; // returns null
}

[mukesh27]

@wujek_bogdan i have checked above issue and found that it's bug in core software. When any WP_Query use fields argument with ids or id=>parent option then system does not set it post variable for that query result and system show null value in result.

[mukesh27]

Patch