From fd8b7faff6e872771dff5849926f4dce1a6079c2 Mon Sep 17 00:00:00 2001
From: Boone Gorges <boonebgorges@git.wordpress.org>
Date: Sat, 3 Jan 2015 02:04:17 +0000
Subject: [PATCH] In `Walker_Category`, don't generate list elements for empty
 cat names.

This change allows the 'list_cats' filter to be used to suppress certain
items in category lists, without creating invalid or superfluous markup.

Props samo9789.
Fixes #16792.

git-svn-id: https://develop.svn.wordpress.org/trunk@31025 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/category-template.php         |  5 +++
 .../tests/category/wpListCategories.php       | 39 +++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 tests/phpunit/tests/category/wpListCategories.php

diff --git a/src/wp-includes/category-template.php b/src/wp-includes/category-template.php
index 7f2c539676..ad66987f7b 100644
--- a/src/wp-includes/category-template.php
+++ b/src/wp-includes/category-template.php
@@ -996,6 +996,11 @@ class Walker_Category extends Walker {
 			$category
 		);
 
+		// Don't generate an element if the category name is empty.
+		if ( ! $cat_name ) {
+			return;
+		}
+
 		$link = '<a href="' . esc_url( get_term_link( $category ) ) . '" ';
 		if ( $args['use_desc_for_title'] && ! empty( $category->description ) ) {
 			/**
diff --git a/tests/phpunit/tests/category/wpListCategories.php b/tests/phpunit/tests/category/wpListCategories.php
new file mode 100644
index 0000000000..dbd4cbb98d
--- /dev/null
+++ b/tests/phpunit/tests/category/wpListCategories.php
@@ -0,0 +1,39 @@
+<?php
+
+/**
+ * @group category
+ */
+class Tests_Category_WpListCategories extends WP_UnitTestCase {
+	/**
+	 * @ticket 16792
+	 */
+	public function test_should_not_create_element_when_cat_name_is_filtered_to_empty_string() {
+		$c1 = $this->factory->category->create( array(
+			'name' => 'Test Cat 1',
+		) );
+		$c2 = $this->factory->category->create( array(
+			'name' => 'Test Cat 2',
+		) );
+
+		add_filter( 'list_cats', array( $this, 'list_cats_callback' ) );
+		$found = wp_list_categories( array(
+			'hide_empty' => false,
+			'echo' => false,
+		) );
+		remove_filter( 'list_cats', array( $this, 'list_cats_callback' ) );
+
+		$this->assertContains( "cat-item-$c2", $found );
+		$this->assertContains( 'Test Cat 2', $found );
+
+		$this->assertNotContains( "cat-item-$c1", $found );
+		$this->assertNotContains( 'Test Cat 1', $found );
+	}
+
+	public function list_cats_callback( $cat ) {
+		if ( 'Test Cat 1' === $cat ) {
+			return '';
+		}
+
+		return $cat;
+	}
+}