Fix for Windows: std.os.windows.DeleteFile()

lib/std/fs/test.zig

@@ -813,3 +813,26 @@ fn run_lock_file_test(contexts: []FileLockTestContext) !void {
         try threads.append(try std.Thread.spawn(ctx, FileLockTestContext.run));
     }
 }
+
+test "deleteDir" {
+    var tmp_dir = tmpDir(.{});
+    defer tmp_dir.cleanup();
+
+    // deleting a non-existent directory
+    testing.expectError(error.FileNotFound, tmp_dir.dir.deleteDir("test_dir"));
+
+    var dir = try tmp_dir.dir.makeOpenPath("test_dir", .{});
+    var file = try dir.createFile("test_file", .{});
+    file.close();
+    dir.close();
+
+    // deleting a non-empty directory
+    testing.expectError(error.DirNotEmpty, tmp_dir.dir.deleteDir("test_dir"));
+
+    dir = try tmp_dir.dir.openDir("test_dir", .{});
+    try dir.deleteFile("test_file");
+    dir.close();
+
+    // deleting an empty directory
+    try tmp_dir.dir.deleteDir("test_dir");
+}

lib/std/os/windows.zig

@@ -764,6 +764,7 @@ pub const DeleteFileError = error{
     Unexpected,
     NotDir,
     IsDir,
+    DirNotEmpty,
 };
 
 pub const DeleteFileOptions = struct {
@@ -818,14 +819,29 @@ pub fn DeleteFile(sub_path_w: []const u16, options: DeleteFileOptions) DeleteFil
         0,
     );
     switch (rc) {
-        .SUCCESS => return CloseHandle(tmp_handle),
+        .SUCCESS => CloseHandle(tmp_handle),
         .OBJECT_NAME_INVALID => unreachable,
         .OBJECT_NAME_NOT_FOUND => return error.FileNotFound,
         .INVALID_PARAMETER => unreachable,
         .FILE_IS_A_DIRECTORY => return error.IsDir,
         .NOT_A_DIRECTORY => return error.NotDir,
         else => return unexpectedStatus(rc),
     }
+
+    // If a directory fails to be deleted, CloseHandle will still report success
+    // Check if the directory still exists and return error.DirNotEmpty if true
+    if (options.remove_dir) {
+        var basic_info: FILE_BASIC_INFORMATION = undefined;
+        switch (ntdll.NtQueryAttributesFile(&attr, &basic_info)) {
+            .SUCCESS => return error.DirNotEmpty,
+            .OBJECT_NAME_NOT_FOUND => return,
+            .OBJECT_PATH_NOT_FOUND => return,
+            .INVALID_PARAMETER => unreachable,
+            .ACCESS_DENIED => return error.AccessDenied,
+            .OBJECT_PATH_SYNTAX_BAD => unreachable,
+            else => |urc| return unexpectedStatus(urc),
+        }
+    }
 }
 
 pub const MoveFileError = error{ FileNotFound, Unexpected };