chenhg5/cc-connect · error

telegram: invalid preview handle type %T

Error message

telegram: invalid preview handle type %T

What it means

DeletePreviewMessage requires the previewHandle argument to be a *telegramPreviewHandle; this error is returned when it is not. Like the reply-context check, it is a contract violation caught at runtime via a type assertion, with %T exposing the offending type.

Source

Thrown at platform/telegram/telegram.go:1332

			// Handle message too long: first chunk with buttons, rest without
			slog.Warn("telegram: message too long, splitting into chunks",
				"method", "SendWithButtons",
				"html_len", len(html),
			)
			return p.sendChunkedWithButtons(ctx, bot, rc, html, rows)
		}
		if err != nil {
			return fmt.Errorf("telegram: sendWithButtons: %w", err)
		}
	}
	return nil
}

// DeletePreviewMessage deletes a stale preview message so the caller can send a fresh one.
func (p *Platform) DeletePreviewMessage(ctx context.Context, previewHandle any) error {
	h, ok := previewHandle.(*telegramPreviewHandle)
	if !ok {
		return fmt.Errorf("telegram: invalid preview handle type %T", previewHandle)
	}
	bot, err := p.connectedBot("delete preview")
	if err != nil {
		return err
	}
	_, err = bot.DeleteMessage(ctx, &tgbot.DeleteMessageParams{ChatID: h.chatID, MessageID: h.messageID})
	if err != nil {
		slog.Debug("telegram: delete preview message failed", "error", err)
	}
	return err
}

func (p *Platform) downloadFile(fileID string) ([]byte, error) {
	bot, err := p.connectedBot("download file")
	if err != nil {
		return nil, err
	}
	ctx := context.Background()

View on GitHub (pinned to 4000b2338a)

Solutions

  1. Pass the *telegramPreviewHandle exactly as returned by the platform's preview-message send API.
  2. Fix the code path that produced the wrong handle type — check the %T output against platform/telegram's handle type.
  3. Keep platform-specific handles scoped to their platform's code paths.
  4. If handles cross a serialization boundary, store the chatID/messageID fields and rebuild the handle on this side.

Example fix

// before
platform.DeletePreviewMessage(ctx, genericHandle)
// after
h, ok := genericHandle.(*telegram.PreviewHandle)
if !ok { return fmt.Errorf("unexpected handle %T", genericHandle) }
platform.DeletePreviewMessage(ctx, h)
Defensive patterns

Strategy: type-guard

Validate before calling

if handle == nil { return errors.New("nil preview handle") }

Type guard

func asTelegramPreviewHandle(v any) (*telegramPreviewHandle, bool) {
    h, ok := v.(*telegramPreviewHandle)
    return h, ok
}

Try / catch

h, ok := previewHandle.(*telegramPreviewHandle)
if !ok {
    return fmt.Errorf("telegram: invalid preview handle type %T", previewHandle)
}

Prevention

When it happens

Trigger: Calling p.DeletePreviewMessage(ctx, handle) with a handle produced by a different platform adapter, a plain struct copy instead of a pointer, or nil.

Common situations: Storing preview handles from multiple platforms in one map keyed by session and passing the wrong one; serializing/deserializing handles so the concrete pointer type is lost; passing the string message ID directly instead of the handle object.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of chenhg5/cc-connect@4000b2338a (2026-09-06). Data as JSON: /api/errors/684384962d2d8e82. Report an issue: GitHub.