Function LoadConfigAtStartup

lib/syncthing/utils.go:88–118

LoadConfigAtStartup loads an existing config. If it doesn't yet exist, it creates a default one. Otherwise it checks the version, and archives and upgrades the config if necessary or returns an error, if the version isn't compatible.

(path string, cert tls.Certificate, evLogger events.Logger, allowNewerConfig, skipPortProbing bool)

// upgrades the config if necessary or returns an error, if the version
// isn't compatible.
func LoadConfigAtStartup(path string, cert tls.Certificate, evLogger events.Logger, allowNewerConfig, skipPortProbing bool) (config.Wrapper, error) {
	myID := protocol.NewDeviceID(cert.Certificate[0])
	cfg, originalVersion, err := config.Load(path, myID, evLogger)
	if fs.IsNotExist(err) {
		cfg, err = DefaultConfig(path, myID, evLogger, skipPortProbing)
		if err != nil {
			return nil, fmt.Errorf("failed to generate default config: %w", err)
		}
		err = cfg.Save()
		if err != nil {
			return nil, fmt.Errorf("failed to save default config: %w", err)
		}
		slog.Info("Default config saved; edit to taste (with Syncthing stopped) or use the GUI", slogutil.FilePath(cfg.ConfigPath()))
	} else if errors.Is(err, io.EOF) {
		return nil, errors.New("failed to load config: unexpected end of file. Truncated or empty configuration?")
	} else if err != nil {
		return nil, fmt.Errorf("failed to load config: %w", err)
	}

	if originalVersion != config.CurrentVersion {
		if originalVersion > config.CurrentVersion && !allowNewerConfig {
			return nil, fmt.Errorf("config file version (%d) is newer than supported version (%d); if this is expected, use --allow-newer-config to override", originalVersion, config.CurrentVersion)
		}
		err = archiveAndSaveConfig(cfg, originalVersion)
		if err != nil {
			return nil, fmt.Errorf("config archive: %w", err)
		}
	}

	return cfg, nil
}

func archiveAndSaveConfig(cfg config.Wrapper, originalVersion int) error {
	// Copy the existing config to an archive copy