From bdda122e7f03059516f678c6f07dc32881beafc7 Mon Sep 17 00:00:00 2001
From: Boone Gorges <boonebgorges@git.wordpress.org>
Date: Sat, 7 Feb 2015 19:49:17 +0000
Subject: [PATCH] In `WP_Query::get_queried_object()`, avoid PHP notices when
 `is_tax` is paired with an empty `tax_query`.

It's possible to have an empty `tax_query` and `is_tax=true` when the initial
query contains a taxonomy var (and is processed as such during
`WP_Query::parse_query()`) but the taxonomy var is unset during a 'parse_query'
callback. While this kind of behavior is not necessarily something we need to
support, we should continue to avoid PHP notices in such cases, as we did prior
to WP 4.1.

Fixes #31246.

git-svn-id: https://develop.svn.wordpress.org/trunk@31366 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/query.php     | 18 ++++++++++--------
 tests/phpunit/tests/query.php | 33 ++++++++++++++++++++++++++++++++-
 2 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/src/wp-includes/query.php b/src/wp-includes/query.php
index c38a11c083..27d8c26fa4 100644
--- a/src/wp-includes/query.php
+++ b/src/wp-includes/query.php
@@ -3900,15 +3900,17 @@ class WP_Query {
 				// For other tax queries, grab the first term from the first clause.
 				$tax_query_in_and = wp_list_filter( $this->tax_query->queried_terms, array( 'operator' => 'NOT IN' ), 'NOT' );
 
-				$queried_taxonomies = array_keys( $tax_query_in_and );
-				$matched_taxonomy = reset( $queried_taxonomies );
-				$query = $tax_query_in_and[ $matched_taxonomy ];
+				if ( ! empty( $tax_query_in_and ) ) {
+					$queried_taxonomies = array_keys( $tax_query_in_and );
+					$matched_taxonomy = reset( $queried_taxonomies );
+					$query = $tax_query_in_and[ $matched_taxonomy ];
 
-				if ( $query['terms'] ) {
-					if ( 'term_id' == $query['field'] ) {
-						$term = get_term( reset( $query['terms'] ), $matched_taxonomy );
-					} else {
-						$term = get_term_by( $query['field'], reset( $query['terms'] ), $matched_taxonomy );
+					if ( $query['terms'] ) {
+						if ( 'term_id' == $query['field'] ) {
+							$term = get_term( reset( $query['terms'] ), $matched_taxonomy );
+						} else {
+							$term = get_term_by( $query['field'], reset( $query['terms'] ), $matched_taxonomy );
+						}
 					}
 				}
 			}
diff --git a/tests/phpunit/tests/query.php b/tests/phpunit/tests/query.php
index 3217ac5c37..c1aa6df309 100644
--- a/tests/phpunit/tests/query.php
+++ b/tests/phpunit/tests/query.php
@@ -91,4 +91,35 @@ class Tests_Query extends WP_UnitTestCase {
 		$this->assertCount( 1, $query->get( 'tag_slug__in' ) );
 		$this->assertEquals( $query->get_queried_object(), $tag );
 	}
-}
\ No newline at end of file
+
+	/**
+	 * @ticket 31246
+	 */
+	public function test_get_queried_object_should_return_null_when_is_tax_is_true_but_the_taxonomy_args_have_been_removed_in_a_parse_query_callback() {
+		// Don't override the args provided below.
+		remove_action( 'pre_get_posts', array( $this, 'pre_get_posts_tax_category_tax_query' ) );
+		register_taxonomy( 'wptests_tax', 'post' );
+		$terms = $this->factory->term->create_many( 2, array(
+			'taxonomy' => 'wptests_tax',
+		) );
+
+		$posts = $this->factory->post->create_many( 2 );
+
+		wp_set_object_terms( $posts[0], array( $terms[0] ), 'wptests_tax' );
+		wp_set_object_terms( $posts[1], array( $terms[1] ), 'wptests_tax' );
+
+		add_action( 'parse_query', array( $this, 'filter_parse_query_to_remove_tax' ) );
+		$q = new WP_Query( array(
+			'fields' => 'ids',
+			'wptests_tax' => $terms[1],
+		) );
+
+		remove_action( 'parse_query', array( $this, 'filter_parse_query_to_remove_tax' ) );
+
+		$this->assertNull( $q->get_queried_object() );
+	}
+
+	public function filter_parse_query_to_remove_tax( $q ) {
+		unset( $q->query_vars['wptests_tax'] );
+	}
+}