pikpak: add file name integrity check during upload

This commit introduces a new validation step to ensure data integrity 
during file uploads.

- The API's returned file name (new.File.Name) is now verified 
  against the requested file name (leaf) immediately after 
  the initial upload ticket is created.
- If a mismatch is detected, the upload process is aborted with an error, 
  and the defer cleanup logic is triggered to delete any partially created file.
- This addresses an unexpected API behavior where numbered suffixes 
  might be appended to filenames even without conflicts.
- This change prevents corrupted or misnamed files from being uploaded 
  without client-side awareness.

backend/pikpak/pikpak.go

@@ -1508,8 +1508,30 @@ func (f *Fs) upload(ctx context.Context, in io.Reader, leaf, dirID, gcid string,
 	}
 	if new.File == nil {
 		return nil, fmt.Errorf("invalid response: %+v", new)
-	} else if new.File.Phase == api.PhaseTypeComplete {
+	}
-		// early return; in case of zero-byte objects
+
+	defer atexit.OnError(&err, func() {
+		fs.Debugf(leaf, "canceling upload: %v", err)
+		if cancelErr := f.deleteObjects(ctx, []string{new.File.ID}, false); cancelErr != nil {
+			fs.Logf(leaf, "failed to cancel upload: %v", cancelErr)
+		}
+		if new.Task != nil {
+			if cancelErr := f.deleteTask(ctx, new.Task.ID, false); cancelErr != nil {
+				fs.Logf(leaf, "failed to cancel upload: %v", cancelErr)
+			}
+			fs.Debugf(leaf, "waiting %v for the cancellation to be effective", taskWaitTime)
+			time.Sleep(taskWaitTime)
+		}
+	})()
+
+	// Note: The API might automatically append a numbered suffix to the filename,
+	// even if a file with the same name does not exist in the target directory.
+	if upName := f.opt.Enc.ToStandardName(new.File.Name); leaf != upName {
+		return nil, fserrors.NoRetryError(fmt.Errorf("uploaded file name mismatch: expected %q, got %q", leaf, upName))
+	}
+
+	// early return; in case of zero-byte objects or uploaded by matched gcid
+	if new.File.Phase == api.PhaseTypeComplete {
 		if acc, ok := in.(*accounting.Account); ok && acc != nil {
 			// if `in io.Reader` is still in type of `*accounting.Account` (meaning that it is unused)
 			// it is considered as a server side copy as no incoming/outgoing traffic occur at all
@@ -1519,18 +1541,6 @@ func (f *Fs) upload(ctx context.Context, in io.Reader, leaf, dirID, gcid string,
 		return new.File, nil
 	}
 
-	defer atexit.OnError(&err, func() {
-		fs.Debugf(leaf, "canceling upload: %v", err)
-		if cancelErr := f.deleteObjects(ctx, []string{new.File.ID}, false); cancelErr != nil {
-			fs.Logf(leaf, "failed to cancel upload: %v", cancelErr)
-		}
-		if cancelErr := f.deleteTask(ctx, new.Task.ID, false); cancelErr != nil {
-			fs.Logf(leaf, "failed to cancel upload: %v", cancelErr)
-		}
-		fs.Debugf(leaf, "waiting %v for the cancellation to be effective", taskWaitTime)
-		time.Sleep(taskWaitTime)
-	})()
-
 	if uploadType == api.UploadTypeForm && new.Form != nil {
 		err = f.uploadByForm(ctx, in, req.Name, size, new.Form, options...)
 	} else if uploadType == api.UploadTypeResumable && new.Resumable != nil {
@@ -1542,6 +1552,9 @@ func (f *Fs) upload(ctx context.Context, in io.Reader, leaf, dirID, gcid string,
 	if err != nil {
 		return nil, fmt.Errorf("failed to upload: %w", err)
 	}
+	if new.Task == nil {
+		return new.File, nil
+	}
 	return new.File, f.waitTask(ctx, new.Task.ID)
 }