General: Cast $max_depth and $depth to an integer in the Walker…

… class.

This ensures that the arguments are correctly interpreted when passed as a query string, i.e. when `wp_parse_args()` is involved. For example, `wp_list_pages( 'depth=0' )` should display a list of all pages to the maximum depth.

Follow-up to [57848].

Props freibergergarcia, peterwilsoncc, ahortin.
Fixes #61749.

git-svn-id: https://develop.svn.wordpress.org/trunk@58812 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-walker.php

@@ -135,6 +135,9 @@ public function display_element( $element, &$children_elements, $max_depth, $dep
 			return;
 		}
 
+		$max_depth = (int) $max_depth;
+		$depth     = (int) $depth;
+
 		$id_field = $this->db_fields['id'];
 		$id       = $element->$id_field;
 
@@ -191,6 +194,8 @@ public function display_element( $element, &$children_elements, $max_depth, $dep
 	public function walk( $elements, $max_depth, ...$args ) {
 		$output = '';
 
+		$max_depth = (int) $max_depth;
+
 		// Invalid parameter or nothing to walk.
 		if ( $max_depth < -1 || empty( $elements ) ) {
 			return $output;
@@ -285,12 +290,14 @@ public function walk( $elements, $max_depth, ...$args ) {
 	 * @return string XHTML of the specified page of elements.
 	 */
 	public function paged_walk( $elements, $max_depth, $page_num, $per_page, ...$args ) {
+		$output = '';
+
+		$max_depth = (int) $max_depth;
+
 		if ( empty( $elements ) || $max_depth < -1 ) {
-			return '';
+			return $output;
 		}
 
-		$output = '';
-
 		$parent_field = $this->db_fields['parent'];
 
 		$count = -1;

tests/phpunit/tests/post/wpListPages.php

@@ -160,6 +160,42 @@ public function test_wp_list_pages_depth() {
 		$this->assertSameIgnoreEOL( $expected, wp_list_pages( $args ) );
 	}
 
+	/**
+	 * @ticket 61749
+	 */
+	public function test_wp_list_pages_depth_equals_zero() {
+		$expected = '<li class="pagenav">Pages<ul><li class="page_item page-item-' . self::$parent_1 . ' page_item_has_children"><a href="' . get_permalink( self::$parent_1 ) . '">Parent 1</a>
+<ul class=\'children\'>
+	<li class="page_item page-item-' . self::$children[ self::$parent_1 ][0] . '"><a href="' . get_permalink( self::$children[ self::$parent_1 ][0] ) . '">Child 1</a></li>
+	<li class="page_item page-item-' . self::$children[ self::$parent_1 ][1] . '"><a href="' . get_permalink( self::$children[ self::$parent_1 ][1] ) . '">Child 2</a></li>
+	<li class="page_item page-item-' . self::$children[ self::$parent_1 ][2] . '"><a href="' . get_permalink( self::$children[ self::$parent_1 ][2] ) . '">Child 3</a></li>
+</ul>
+</li>
+<li class="page_item page-item-' . self::$parent_2 . ' page_item_has_children"><a href="' . get_permalink( self::$parent_2 ) . '">Parent 2</a>
+<ul class=\'children\'>
+	<li class="page_item page-item-' . self::$children[ self::$parent_2 ][0] . '"><a href="' . get_permalink( self::$children[ self::$parent_2 ][0] ) . '">Child 1</a></li>
+	<li class="page_item page-item-' . self::$children[ self::$parent_2 ][1] . '"><a href="' . get_permalink( self::$children[ self::$parent_2 ][1] ) . '">Child 2</a></li>
+	<li class="page_item page-item-' . self::$children[ self::$parent_2 ][2] . '"><a href="' . get_permalink( self::$children[ self::$parent_2 ][2] ) . '">Child 3</a></li>
+</ul>
+</li>
+<li class="page_item page-item-' . self::$parent_3 . ' page_item_has_children"><a href="' . get_permalink( self::$parent_3 ) . '">Parent 3</a>
+<ul class=\'children\'>
+	<li class="page_item page-item-' . self::$children[ self::$parent_3 ][0] . '"><a href="' . get_permalink( self::$children[ self::$parent_3 ][0] ) . '">Child 1</a></li>
+	<li class="page_item page-item-' . self::$children[ self::$parent_3 ][1] . '"><a href="' . get_permalink( self::$children[ self::$parent_3 ][1] ) . '">Child 2</a></li>
+	<li class="page_item page-item-' . self::$children[ self::$parent_3 ][2] . '"><a href="' . get_permalink( self::$children[ self::$parent_3 ][2] ) . '">Child 3</a></li>
+</ul>
+</li>
+</ul></li>';
+
+		// Execute wp_list_pages() with a string to force calling wp_parse_args().
+		ob_start();
+		wp_list_pages( 'depth=0' );
+		$output = ob_get_clean();
+
+		// If depth equals 0, all levels should be displayed.
+		$this->assertSameIgnoreEOL( $expected, $output );
+	}
+
 	public function test_wp_list_pages_show_date() {
 		$args = array(
 			'echo'      => false,