[wp-trac] [WordPress Trac] #49799: get_the_terms() object term cache check too strict?

[WordPress Trac]

#49799: get_the_terms() object term cache check too strict?
--------------------------+------------------------------------------------
 Reporter:  dingo_d       |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Taxonomy      |    Version:  5.4
 Severity:  normal        |   Keywords:  dev-feedback 2nd-opinion has-patch
  Focuses:                |
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 I ran into a weird issue when doing integration tests on one of a client's
 project.

 I was setting up custom post and custom taxonomy from the factory (for
 posts I used the default one, and for custom taxonomy I have created my
 own factory that extends `WP_UnitTest_Factory_For_Term`), set everything
 up, but the part of the plugins code that used `get_the_terms` returned
 nothing. So after racking my brains, I tried `wp_get_post_terms`, and lo
 and behold, this worked (the test posts had assigned terms for them, I
 checked before invoking my function I needed to test using
 `get_the_terms`).

 So something was up with caching. I started to dig and it turned out that

 {{{#!php
 $terms = get_object_term_cache( $post->ID, $taxonomy );
 }}}

 inside `wp-includes/category-template.php`

 returned an empty array.

 Now, since the line 1246 says

 {{{#!php
 if ( false === $terms ) {
 }}}

 The empty array, while being a ''falsy'' value, it's not a `false` value
 (https://3v4l.org/RVuG7), so the above check will return false and the
 returned value from the `get_the_terms` function will be `false`.

 So when I 'loosened' the condition in my test suite WP, the `$terms =
 wp_get_object_terms( $post->ID, $taxonomy );`
 works, and I get my terms inside the tests.

 If the condition is loosened, nothing seems to be lost in terms of
 checking the emptiness of the terms from the term object cache (if it's
 full, it's `false` all the times https://3v4l.org/34UQk).

 Now, on the face value, this could be the oddity of the test suite (which
 in my case is set up using wpcli scaffold command), but I'm thinking that
 changing this requirement cannot hurt (from what I can tell) in the long
 run.

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Ticket URL: <https://core.trac.wordpress.org/ticket/49799>
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