Filesystem API: Return `false` for empty paths in FTP `::exists()` methods.

When `ftp_nlist()` receives an empty path, it checks the current working directory and may return `true`.

This affects:
* `WP_Filesystem_FTPext::exists()`
* `WP_Filesystem_ftpsockets::exists()`

As the purpose of the API is to provide a consistent interface for various filesystem implementations, this commit updates the affected methods to returns `false` when an empty path is provided, bringing consistency with the other filesystem abstraction classes, specifically `WP_Filesystem_Direct` and `WP_Filesystem_SSH2`.

Follow-up to [6779], [11821], [25274], [31815].

Props mkox, costdev, Zdrobau, dd32, pbiron, azaozz, mukesh27, SergeyBiryukov.
Fixes #33058.
Built from https://develop.svn.wordpress.org/trunk@55556


git-svn-id: http://core.svn.wordpress.org/trunk@55068 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/class-wp-filesystem-ftpext.php

@@ -419,11 +419,22 @@ class WP_Filesystem_FTPext extends WP_Filesystem_Base {
 	 * Checks if a file or directory exists.
 	 *
 	 * @since 2.5.0
+	 * @since 6.3.0 Returns false for an empty path.
 	 *
 	 * @param string $path Path to file or directory.
 	 * @return bool Whether $path exists or not.
 	 */
 	public function exists( $path ) {
+		/*
+		 * Check for empty path. If ftp_nlist() receives an empty path,
+		 * it checks the current working directory and may return true.
+		 *
+		 * See https://core.trac.wordpress.org/ticket/33058.
+		 */
+		if ( '' === $path ) {
+			return false;
+		}
+
 		$list = ftp_nlist( $this->link, $path );
 
 		if ( empty( $list ) && $this->is_dir( $path ) ) {

wp-admin/includes/class-wp-filesystem-ftpsockets.php

@@ -421,11 +421,22 @@ class WP_Filesystem_ftpsockets extends WP_Filesystem_Base {
 	 * Checks if a file or directory exists.
 	 *
 	 * @since 2.5.0
+	 * @since 6.3.0 Returns false for an empty path.
 	 *
 	 * @param string $path Path to file or directory.
 	 * @return bool Whether $path exists or not.
 	 */
 	public function exists( $path ) {
+		/*
+		 * Check for empty path. If ftp::nlist() receives an empty path,
+		 * it checks the current working directory and may return true.
+		 *
+		 * See https://core.trac.wordpress.org/ticket/33058.
+		 */
+		if ( '' === $path ) {
+			return false;
+		}
+
 		$list = $this->ftp->nlist( $path );
 
 		if ( empty( $list ) && $this->is_dir( $path ) ) {

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.3-alpha-55555';
+$wp_version = '6.3-alpha-55556';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.