kovidgoyal/kitty · error

%s is not a valid type signature: %w

Error message

%s is not a valid type signature: %w

What it means

ParseValueWithSignature strips a leading '@' from the signature and hands it to dbus.ParseSignature; if the remaining string is not a valid D-Bus type signature (e.g. 'uu' where 'u' is expected, or 'x'), this error is returned.

Source

Thrown at kittens/desktop_ui/portal.go:237

		"ChangeSetting": {{"namespace", "s", false}, {"key", "s", false}, {"value", "v", false}},
		"RemoveSetting": {{"namespace", "s", false}, {"key", "s", false}},
	}
	props["version"].Value = uint32(1)
	if err = ExportInterface(self.bus, self, CHANGE_SETTINGS_INTERFACE, KITTY_OBJECT_PATH, methods, props, nil); err != nil {
		return
	}
	return
}

func ParseValueWithSignature(value, value_type_signature string) (v dbus.Variant, err error) {
	var s dbus.Signature
	if value_type_signature != "" {
		if value_type_signature[0] == '@' {
			value_type_signature = value_type_signature[1:]
		}
		s, err = dbus.ParseSignature(value_type_signature)
		if err != nil {
			return dbus.Variant{}, fmt.Errorf("%s is not a valid type signature: %w", value_type_signature, err)
		}
	}
	v, err = dbus.ParseVariant(value, s)
	if err != nil {
		if value_type_signature == "" {
			return dbus.Variant{}, fmt.Errorf("could not guess the data type of: %s with error: %w", value, err)
		}
		return dbus.Variant{}, fmt.Errorf("%s is not a valid value for signature: %#v with error: %w", value, value_type_signature, err)
	}
	return v, nil
}

func ParseValue(value string) (dbus.Variant, error) {
	return ParseValueWithSignature(value, "")
}

type ShowSettingsOptions struct {
	AsJson             bool

View on GitHub (pinned to 6d5d0c4406)

Solutions

1. Use a single valid D-Bus signature character/structure, e.g. '@u', '@s', '@b', '@(ii)'
2. Consult the GVariant type string documentation
3. Omit the signature entirely and let ParseValue guess the type

Example fix

# before
kitten desktop-ui set ns key --value-type '@uint32' 1
# after
kitten desktop-ui set ns key --value-type '@u' 1

sig := strings.TrimPrefix(sig, "@")
if _, err := dbus.ParseSignature(sig); err != nil {
    return fmt.Errorf("bad signature %q", sig)
}

func isValidSignature(s string) bool {
    s = strings.TrimPrefix(s, "@")
    _, err := dbus.ParseSignature(s)
    return err == nil
}

When it happens

Trigger: Calling set with a --value-type/signature argument like '@q', '@ii', or an empty-after-@ signature.

Common situations: Users unfamiliar with GVariant type strings passing full type names ('uint32') instead of signature characters ('u'), or concatenating multiple type characters.

Related errors

• could not guess the data type of: %s with error: %w
• %s is not a valid value for signature: %#v with error: %w
• failed to export interface: %s at object path: %s with error
• failed to export properties with error: %w
• failed to export introspected methods with error: %w

AI-assisted analysis of kovidgoyal/kitty@6d5d0c4406 (2026-08-27). Data as JSON: /api/errors/8c4ec1e920da5559. Report an issue: GitHub.