Taxonomy: Introduce `term_exists_default_query_args` filter.

In [52921] `term_exists` was converted to use `get_terms`. This change adds a filter called `term_exists_default_query_args` 
to the `term_exists` function to allow developers to modify the arguments passed to `get_terms` before the query is run.

Props Chouby, Spacedmonkey, peterwilsoncc.
Fixes #55439.



Built from https://develop.svn.wordpress.org/trunk@52987


git-svn-id: http://core.svn.wordpress.org/trunk@52576 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/taxonomy.php

@@ -1559,6 +1559,18 @@ function term_exists( $term, $taxonomy = '', $parent = null ) {
 		$defaults['fields']   = 'all';
 	}
 
+	/**
+	 * Filters default arguments for checking if term exists.
+	 *
+	 * @since 6.0.0
+	 *
+	 * @param array      $defaults An array of arguments for term_exists.
+	 * @param int|string $term     The term to check. Accepts term ID, slug, or name.
+	 * @param string     $taxonomy The taxonomy name to use. An empty string indicates the search is against all taxonomies.
+	 * @param int|null   $parent   ID of parent term under which to confine the exists search. Null indicates the search is unconfined.
+	 */
+	$defaults = apply_filters( 'term_exists_default_query_args', $defaults, $term, $taxonomy, $parent );
+
 	if ( is_int( $term ) ) {
 		if ( 0 === $term ) {
 			return 0;

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.0-alpha-52986';
+$wp_version = '6.0-alpha-52987';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.