Fix RemoveUploaded within WP_XMLRPC_UnitTestCase

Because the parent set_up was a trait, it was being bypassed, so the
uploads were not scanned and everything was being deleted.

includes/src/Traits/RemoveUploaded.php

@@ -15,12 +15,15 @@
  *
  */
 trait RemoveUploaded {
-	protected static $ignore_files = [];
+	/**
+	 * @var string[]|null
+	 */
+	protected static ?array $ignore_files = null;
 
 
 	public function set_up() {
 		parent::set_up();
-		if ( [] === static::$ignore_files ) {
+		if ( null === static::$ignore_files ) {
 			// Only scan the directory once per test run.
 			static::$ignore_files = $this->scan_user_uploads();
 		}
@@ -38,13 +41,17 @@ public function tear_down(): void {
 	 *
 	 * This method works in tandem with the `set_up()` and `rmdir()` methods:
 	 * - `set_up()` scans the `uploads` directory before every test, and stores
-	 *   its contents inside of the `$ignore_files` property.
+	 *   its contents inside the `$ignore_files` property.
 	 * - `rmdir()` and its helper methods only delete files that are not listed
 	 *   in the `$ignore_files` property. If called during `tear_down()` in tests,
 	 *   this will only delete files added during the previously run test.
 	 */
 	public function remove_added_uploads(): void {
 		$uploads = wp_upload_dir();
+		if ( null === static::$ignore_files ) {
+			static::$ignore_files = $this->scan_user_uploads();
+		}
+
 		Files::instance()->rmdir( $uploads['basedir'], static::$ignore_files );
 	}
 
@@ -54,16 +61,15 @@ public function remove_added_uploads(): void {
 	 *
 	 * @since 4.0.0
 	 *
-	 * @return array List of file paths.
+	 * @return string[] List of file paths.
 	 */
 	public function scan_user_uploads(): array {
 		static $files = [];
-		if ( ! empty( $files ) ) {
+		if ( [] !== $files ) {
 			return $files;
 		}
 
 		$uploads = wp_upload_dir();
-		$files = Files::instance()->files_in_dir( $uploads['basedir'] );
-		return $files;
+		return Files::instance()->files_in_dir( $uploads['basedir'] );
 	}
 }

includes/testcase-xmlrpc.php

@@ -7,15 +7,17 @@
 require_once ABSPATH . WPINC . '/class-wp-xmlrpc-server.php';
 
 abstract class WP_XMLRPC_UnitTestCase extends WP_UnitTestCase {
-	use RemoveUploaded;
+	use RemoveUploaded {
+		set_up as protected remove_uploaded_set_up;
+	}
 
 	/**
 	 * @var wp_xmlrpc_server
 	 */
 	protected $myxmlrpcserver;
 
 	public function set_up() {
-		parent::set_up();
+		$this->remove_uploaded_set_up();
 
 		add_filter( 'pre_option_enable_xmlrpc', '__return_true' );