yudai/gotty · error

failed to marshal preferences as JSON

Error message

failed to marshal preferences as JSON

What it means

Wrapped json.Marshal error inside the WithMasterPreferences option: the preferences value passed by the server (xterm.js preferences) is not JSON-serializable — e.g. contains channels, funcs, or cyclic structures — so the option rejects itself and aborts webtty.New.

Source

Thrown at webtty/option.go:57

		wt.windowTitle = windowTitle
		return nil
	}
}

// WithReconnect enables reconnection on the master side.
func WithReconnect(timeInSeconds int) Option {
	return func(wt *WebTTY) error {
		wt.reconnect = timeInSeconds
		return nil
	}
}

// WithMasterPreferences sets an optional configuration of master.
func WithMasterPreferences(preferences interface{}) Option {
	return func(wt *WebTTY) error {
		prefs, err := json.Marshal(preferences)
		if err != nil {
			return errors.Wrapf(err, "failed to marshal preferences as JSON")
		}
		wt.masterPrefs = prefs
		return nil
	}
}

View on GitHub (pinned to a080c85cbc)

Solutions

1. Pass a plain map/struct of JSON-compatible types as preferences
2. Marshal the preferences once at config load to catch bad types early
3. Reject unsupported preference types at the config layer with a clear message

When it happens

Trigger: Thrown at webtty/option.go:57 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of yudai/gotty@a080c85cbc (2026-09-02). Data as JSON: /api/errors/5135c18276214870. Report an issue: GitHub.