From fdeed90e77b9ad3f1de7246c9e23450a4878322c Mon Sep 17 00:00:00 2001
From: Boone Gorges <boonebgorges@git.wordpress.org>
Date: Fri, 18 Dec 2015 17:43:46 +0000
Subject: [PATCH] Ensure `get_terms()` results are unique when using
 'meta_query'.

The introduction of 'meta_query' to `get_terms()` in 4.4 made it possible for
`get_terms()` to erroneously return duplicate results. To address the issue,
we add the `DISTINCT` keyword to the SQL query when a 'meta_query' parameter
has been provided.

Props @jadpm.
Fixes #35137.

git-svn-id: https://develop.svn.wordpress.org/trunk@36003 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/taxonomy.php          |  7 +++++--
 tests/phpunit/tests/term/getTerms.php | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/src/wp-includes/taxonomy.php b/src/wp-includes/taxonomy.php
index 84cc91af8f..42164528fc 100644
--- a/src/wp-includes/taxonomy.php
+++ b/src/wp-includes/taxonomy.php
@@ -1353,12 +1353,14 @@ function get_terms( $taxonomies, $args = '' ) {
 
 	// Meta query support.
 	$join = '';
+	$distinct = '';
 	if ( ! empty( $args['meta_query'] ) ) {
 		$mquery = new WP_Meta_Query( $args['meta_query'] );
 		$mq_sql = $mquery->get_sql( 'term', 't', 'term_id' );
 
 		$join  .= $mq_sql['join'];
 		$where .= $mq_sql['where'];
+		$distinct .= "DISTINCT";
 	}
 
 	$selects = array();
@@ -1408,7 +1410,7 @@ function get_terms( $taxonomies, $args = '' ) {
 
 	$join .= " INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id";
 
-	$pieces = array( 'fields', 'join', 'where', 'orderby', 'order', 'limits' );
+	$pieces = array( 'fields', 'join', 'where', 'distinct', 'orderby', 'order', 'limits' );
 
 	/**
 	 * Filter the terms query SQL clauses.
@@ -1424,11 +1426,12 @@ function get_terms( $taxonomies, $args = '' ) {
 	$fields = isset( $clauses[ 'fields' ] ) ? $clauses[ 'fields' ] : '';
 	$join = isset( $clauses[ 'join' ] ) ? $clauses[ 'join' ] : '';
 	$where = isset( $clauses[ 'where' ] ) ? $clauses[ 'where' ] : '';
+	$distinct = isset( $clauses[ 'distinct' ] ) ? $clauses[ 'distinct' ] : '';
 	$orderby = isset( $clauses[ 'orderby' ] ) ? $clauses[ 'orderby' ] : '';
 	$order = isset( $clauses[ 'order' ] ) ? $clauses[ 'order' ] : '';
 	$limits = isset( $clauses[ 'limits' ] ) ? $clauses[ 'limits' ] : '';
 
-	$query = "SELECT $fields FROM $wpdb->terms AS t $join WHERE $where $orderby $order $limits";
+	$query = "SELECT $distinct $fields FROM $wpdb->terms AS t $join WHERE $where $orderby $order $limits";
 
 	// $args can be anything. Only use the args defined in defaults to compute the key.
 	$key = md5( serialize( wp_array_slice_assoc( $args, array_keys( $defaults ) ) ) . serialize( $taxonomies ) . $query );
diff --git a/tests/phpunit/tests/term/getTerms.php b/tests/phpunit/tests/term/getTerms.php
index f3e9316301..bcd348586b 100644
--- a/tests/phpunit/tests/term/getTerms.php
+++ b/tests/phpunit/tests/term/getTerms.php
@@ -1570,6 +1570,30 @@ class Tests_Term_getTerms extends WP_UnitTestCase {
 		$this->assertEqualSets( array( $terms[0], $terms[1] ), $found );
 	}
 
+	/**
+	 * @ticket 35137
+	 */
+	public function test_meta_query_should_not_return_duplicates() {
+		register_taxonomy( 'wptests_tax', 'post' );
+		$terms = self::factory()->term->create_many( 1, array( 'taxonomy' => 'wptests_tax' ) );
+		add_term_meta( $terms[0], 'foo', 'bar' );
+		add_term_meta( $terms[0], 'foo', 'ber' );
+
+		$found = get_terms( 'wptests_tax', array(
+			'hide_empty' => false,
+			'meta_query' => array(
+				array(
+					'key' => 'foo',
+					'value' => 'bur',
+					'compare' => '!=',
+				),
+			),
+			'fields' => 'ids',
+		) );
+
+		$this->assertEqualSets( array( $terms[0] ), $found );
+	}
+
 	/**
 	 * @ticket 14162
 	 */