muesli/duf · error

unknown theme

Error message

unknown theme: %s

What it means

loadTheme builds a fixed map of supported themes ("dark", "light", "ansi") and returns this error when the requested theme name is not a key in that map. It is a simple lookup failure: the theme string passed in (typically from a CLI flag or config) does not match any registered theme. The error message includes the offending theme name so the caller can see what was rejected.

Solutions

1. Run with one of the supported theme names: dark, light, or ansi
2. Check the exact spelling and casing — the lookup is case-sensitive, so "Dark" fails
3. If the theme came from a config file or env var, fix or remove that value
4. List available themes from the tool's help output (or themes map in themes.go) and pick a valid one
5. If a new theme is genuinely needed, add it to the themes map in loadTheme (or contribute it upstream)

Example fix

// before
loadTheme("Dark") // -> unknown theme: Dark
// after
loadTheme("dark") // valid: dark | light | ansi

var validThemes = []string{"dark", "light", "ansi"}
func isValidTheme(name string) bool {
	for _, t := range validThemes {
		if t == name {
			return true
		}
	}
	return false
}
// before calling: if !isValidTheme(themeName) { themeName = "dark" }

func knownTheme(name string) (string, bool) {
	switch name {
	case "dark", "light", "ansi":
		return name, true
	}
	return "", false
}

theme, err := loadTheme(name)
if err != nil {
	fmt.Fprintf(os.Stderr, "warning: %v; falling back to default theme %q\n", err, defaultThemeName())
	theme, err = loadTheme(defaultThemeName())
	if err != nil {
		fmt.Fprintln(os.Stderr, "fatal: default theme failed:", err)
		os.Exit(1)
	}
}

When it happens

Trigger: Calling loadTheme(name) where name is not exactly "dark", "light", or "ansi" — e.g. loadTheme("solarized"), loadTheme("Dark") (case mismatch), loadTheme(""), or a misspelled name like "dakr". main reaches this whenever a user supplies an unlisted -theme/--theme flag value or a config file sets theme to an unknown name.

Common situations: A user passes --theme=monokai expecting extra built-in themes; a config file written for another tool carries a theme name this tool doesn't support; a typo or wrong casing ("Dark" vs "dark"); an empty theme value from an unset env var or blank CLI flag; version drift where a theme name was removed/renamed.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• error parsing avail-threshold: invalid option
• error parsing usage-threshold: invalid option
• unknown column: (valid: )
• unknown device group
• unknown style option

AI-assisted analysis of muesli/duf@4636deb4a7 (2026-09-06). Data as JSON: /api/errors/aea2babf10f7b3cc. Report an issue: GitHub.

Appendix: source

Thrown at themes.go:74

		colorBgYellow: env.Color("#fff4d0"),
		colorBgGreen:  env.Color("#e6ffe6"),
	}

	themes["ansi"] = Theme{
		colorRed:      env.Color("9"),
		colorYellow:   env.Color("11"),
		colorGreen:    env.Color("10"),
		colorBlue:     env.Color("12"),
		colorGray:     env.Color("7"),
		colorMagenta:  env.Color("13"),
		colorCyan:     env.Color("8"),
		colorBgRed:    env.Color("1"),
		colorBgYellow: env.Color("3"),
		colorBgGreen:  env.Color("2"),
	}

	if _, ok := themes[theme]; !ok {
		return Theme{}, fmt.Errorf("unknown theme: %s", theme)
	}

	return themes[theme], nil
}

View on GitHub (pinned to 4636deb4a7)