From 52384c2e6bb80a8a96d43dc483f254ca417df618 Mon Sep 17 00:00:00 2001
From: Boone Gorges <boonebgorges@git.wordpress.org>
Date: Thu, 10 Dec 2015 03:34:51 +0000
Subject: [PATCH] Improve handling for `WP_Error` objects in `get_the_terms()`.

`wp_get_object_terms()` can return a `WP_Error` object. As such, the
`get_the_terms()` cache wrapper should handle them properly. To wit:

* Don't try to map an error object to `get_term()`. Introduced in [35032].
* Don't cache an error object as taxonomy relationships. Introduced in at least [16487], maybe earlier.

Props stephenharris.
Fixes #34723.

git-svn-id: https://develop.svn.wordpress.org/trunk@35850 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/category-template.php | 14 +++++++++-----
 tests/phpunit/tests/term.php          |  9 +++++++++
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/wp-includes/category-template.php b/src/wp-includes/category-template.php
index 9b685edb11..68cd74c8e5 100644
--- a/src/wp-includes/category-template.php
+++ b/src/wp-includes/category-template.php
@@ -1148,14 +1148,18 @@ function get_the_terms( $post, $taxonomy ) {
 	$terms = get_object_term_cache( $post->ID, $taxonomy );
 	if ( false === $terms ) {
 		$terms = wp_get_object_terms( $post->ID, $taxonomy );
-		$to_cache = array();
-		foreach ( $terms as $key => $term ) {
-			$to_cache[ $key ] = $term->data;
+		if ( ! is_wp_error( $terms ) ) {
+			$to_cache = array();
+			foreach ( $terms as $key => $term ) {
+				$to_cache[ $key ] = $term->data;
+			}
+			wp_cache_add( $post->ID, $to_cache, $taxonomy . '_relationships' );
 		}
-		wp_cache_add( $post->ID, $to_cache, $taxonomy . '_relationships' );
 	}
 
-	$terms = array_map( 'get_term', $terms );
+	if ( ! is_wp_error( $terms ) ) {
+		$terms = array_map( 'get_term', $terms );
+	}
 
 	/**
 	 * Filter the list of terms attached to the given post.
diff --git a/tests/phpunit/tests/term.php b/tests/phpunit/tests/term.php
index 0d005f38d3..9c6e9655a4 100644
--- a/tests/phpunit/tests/term.php
+++ b/tests/phpunit/tests/term.php
@@ -627,4 +627,13 @@ class Tests_Term extends WP_UnitTestCase {
 		$cat_id2 = self::factory()->category->create( array( 'parent' => $cat_id1 ) );
 		$this->assertWPError( $cat_id2 );
 	}
+
+	/**
+	 * @ticket 34723
+	 */
+	function test_get_the_terms_should_return_wp_error_when_taxonomy_is_unregistered() {
+		$p = self::$post_ids[0];
+		$terms = get_the_terms( $p, 'this-taxonomy-does-not-exist' );
+		$this->assertTrue( is_wp_error( $terms ) );
+	}
 }