From 324748a854d5d52d4a19a0a30671a22fa02fd7ff Mon Sep 17 00:00:00 2001
From: Dominik Schilling <dominikschilling+git@gmail.com>
Date: Thu, 29 Sep 2016 22:36:30 +0000
Subject: [PATCH] Taxonomy: Use `WP_Term_Query` in `get_term_by()`.

`WP_Term_Query` already supports querying terms by 'slug', 'name', and 'term_taxonomy_id'. Its additional arguments allow us to generate nearly the same SQL queries as before.
This change has one yuge benefit: the term queries are now cached.

Add tests to increase coverage of `get_term_by()`.

Props spacedmonkey, boonebgorges, johnjamesjacoby, pento, ocean90.
Fixes #21760.
Built from https://develop.svn.wordpress.org/trunk@38677


git-svn-id: http://core.svn.wordpress.org/trunk@38620 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/taxonomy.php | 54 ++++++++++++++++++++++------------------
 wp-includes/version.php  |  2 +-
 2 files changed, 31 insertions(+), 25 deletions(-)

diff --git a/wp-includes/taxonomy.php b/wp-includes/taxonomy.php
index 5767ebf7a3..a39fa47518 100644
--- a/wp-includes/taxonomy.php
+++ b/wp-includes/taxonomy.php
@@ -927,49 +927,55 @@ function get_term( $term, $taxonomy = '', $output = OBJECT, $filter = 'raw' ) {
  *                      or `$term` was not found.
  */
 function get_term_by( $field, $value, $taxonomy = '', $output = OBJECT, $filter = 'raw' ) {
-	global $wpdb;
 
 	// 'term_taxonomy_id' lookups don't require taxonomy checks.
 	if ( 'term_taxonomy_id' !== $field && ! taxonomy_exists( $taxonomy ) ) {
 		return false;
 	}
 
-	$tax_clause = $wpdb->prepare( "AND tt.taxonomy = %s", $taxonomy );
-
-	if ( 'slug' == $field ) {
-		$_field = 't.slug';
-		$value = sanitize_title($value);
-		if ( empty($value) )
-			return false;
-	} elseif ( 'name' == $field ) {
-		// Assume already escaped
-		$value = wp_unslash($value);
-		$_field = 't.name';
-	} elseif ( 'term_taxonomy_id' == $field ) {
-		$value = (int) $value;
-		$_field = 'tt.term_taxonomy_id';
-
-		// No `taxonomy` clause when searching by 'term_taxonomy_id'.
-		$tax_clause = '';
-	} else {
+	if ( 'id' === $field || 'term_id' === $field ) {
 		$term = get_term( (int) $value, $taxonomy, $output, $filter );
-		if ( is_wp_error( $term ) || is_null( $term ) ) {
+		if ( is_wp_error( $term ) || null === $term ) {
 			$term = false;
 		}
 		return $term;
 	}
 
-	$term = $wpdb->get_row( $wpdb->prepare( "SELECT t.*, tt.* FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id WHERE $_field = %s", $value ) . " $tax_clause LIMIT 1" );
-	if ( ! $term )
+	$args = array(
+		'get'                    => 'all',
+		'number'                 => 1,
+		'taxonomy'               => $taxonomy,
+		'update_term_meta_cache' => false,
+		'orderby'                => 'none',
+	);
+
+	switch ( $field ) {
+		case 'slug' :
+			$args['slug'] = $value;
+			break;
+		case 'name' :
+			$args['name'] = $value;
+			break;
+		case 'term_taxonomy_id' :
+			$args['term_taxonomy_id'] = $value;
+			unset( $args[ 'taxonomy' ] );
+			break;
+		default :
+			return false;
+	}
+
+	$terms = get_terms( $args );
+	if ( is_wp_error( $terms ) || empty( $terms ) ) {
 		return false;
+	}
+
+	$term = array_shift( $terms );
 
 	// In the case of 'term_taxonomy_id', override the provided `$taxonomy` with whatever we find in the db.
 	if ( 'term_taxonomy_id' === $field ) {
 		$taxonomy = $term->taxonomy;
 	}
 
-	wp_cache_add( $term->term_id, $term, 'terms' );
-
 	return get_term( $term, $taxonomy, $output, $filter );
 }
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 9d1e3dcf2f..2d06feb5e6 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-alpha-38676';
+$wp_version = '4.7-alpha-38677';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.