get_terms() doesn't work on Multisite

[AustinTBiggs]

Today I found a bug within WordPress Multisite functions.

From a subsite I tried accessing the terms of a custom taxonomy on site #1. This worked using get_term_by(), but not with get_terms(). WordPress returns with "Invalid Taxonomy", however I knew the taxonomy existed.

In order to overcome this, I had to create a custom taxonomy on the subsite with the exact same name. Then WordPress successfully returned the terms from site #1.

Below is my code:

switch_to_blog(1);
								
$taxonomy = array( 'custom_taxonomy' );
						
$args = array(
	'hide_empty' => false, 
	'exclude' => array(), 
	'exclude_tree' => array(), 
	'include' => array(),
	'number' => '', 
	'fields' => 'all', 
); 
						
$terms = get_terms( $taxonomy, $args );
						
var_dump($terms);
						
restore_current_blog();

[dd32]

See #32526 & #20541

Ultimately this is an invalid use-case, Taxonomies must be registered during the pageload to be accessible.