Query: Check that taxonomy query var is a string in WP_Query::parse_tax_query().

This prevents a fatal error from `urldecode()` in `wp_basename()` if an array is passed instead.

Follow-up to [15732], [15824], [15825], [15923], [16155], [50565], [60927].

Props patricedefago, alexodiy, SergeyBiryukov.
Fixes #64870.

git-svn-id: https://develop.svn.wordpress.org/trunk@62047 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/class-wp-query.php

@@ -1189,7 +1189,7 @@ public function parse_tax_query( &$query_vars ) {
 					'field'    => 'slug',
 				);
 
-				if ( ! empty( $t->rewrite['hierarchical'] ) ) {
+				if ( is_string( $query_vars[ $t->query_var ] ) && ! empty( $t->rewrite['hierarchical'] ) ) {
 					$query_vars[ $t->query_var ] = wp_basename( $query_vars[ $t->query_var ] );
 				}
 

tests/phpunit/tests/query/parseQuery.php

@@ -233,4 +233,35 @@ public function test_parse_query_attachment_id_nonscalar() {
 
 		$this->assertEmpty( $q->query_vars['attachment_id'] );
 	}
+
+	/**
+	 * Tests that a fatal error is not thrown when a hierarchical taxonomy query var
+	 * passed to wp_basename() in ::parse_tax_query() is an array instead of a string.
+	 *
+	 * The message that we should not see:
+	 * `TypeError: urldecode(): Argument #1 ($string) must be of type string, array given`.
+	 *
+	 * @ticket 64870
+	 */
+	public function test_parse_query_hierarchical_taxonomy_query_var_array() {
+		register_taxonomy(
+			'wptests_tax',
+			'post',
+			array(
+				'query_var' => 'wptests_tax',
+				'rewrite'   => array( 'hierarchical' => true ),
+				'public'    => true,
+			)
+		);
+
+		$q = new WP_Query(
+			array(
+				'wptests_tax' => array( 'term-a', 'term-b' ),
+			)
+		);
+
+		unregister_taxonomy( 'wptests_tax' );
+
+		$this->assertIsArray( $q->posts );
+	}
 }