kataras/iris · error

catalog: empty languages

Error message

catalog: empty languages

What it means

catalog.NewCatalog builds a Catalog from an ordered slice of golang.org/x/text language.Tag values; the first becomes the default. An empty slice means there is no default language, so construction is rejected with this error.

Source

Thrown at i18n/internal/catalog.go:52

type Options struct {
	// Left delimiter for template messages.
	Left string
	// Right delimeter for template messages.
	Right string
	// Enable strict mode.
	Strict bool
	// Optional functions for template messages per locale.
	Funcs func(context.Locale) template.FuncMap
	// Optional function to be called when no message was found.
	DefaultMessageFunc MessageFunc
	// Customize the overall behavior of the plurazation feature.
	PluralFormDecoder PluralFormDecoder
}

// NewCatalog returns a new Catalog based on the registered languages and the loader options.
func NewCatalog(languages []language.Tag, opts Options) (*Catalog, error) { // ordered languages, the first should be the default one.
	if len(languages) == 0 {
		return nil, fmt.Errorf("catalog: empty languages")
	}

	if opts.Left == "" {
		opts.Left = "{{"
	}

	if opts.Right == "" {
		opts.Right = "}}"
	}

	if opts.PluralFormDecoder == nil {
		opts.PluralFormDecoder = DefaultPluralFormDecoder
	}

	builder := catalog.NewBuilder(catalog.Fallback(languages[0]))

	locales := make([]*Locale, 0, len(languages))
	for idx, tag := range languages {

View on GitHub (pinned to 7bedaf55a0)

Solutions

1. Pass at least one language tag, with the default first, to i18n.New
2. Fix the glob/path or directory scan so translation files are actually discovered
3. Ship locale files with the deployment (embed them or copy into the container)
4. Log the detected languages before constructing the catalog to catch empty detection early

Example fix

// before
i, err := i18n.New(i18n.Glob("./locales/*.yml")) // dir empty -> empty languages
// after
if _, err := os.Stat("./locales/en.yml"); err != nil { log.Fatal("missing default locale") }
i, err := i18n.New(i18n.Glob("./locales/*.yml"), "en", "el")

if len(languages) == 0 {
    return errors.New("i18n: no languages detected; check locale directory")
}

cat, err := i18n.New(loader, langs...)
if err != nil && strings.Contains(err.Error(), "empty languages") {
    log.Fatal("no translation files found; verify locale path and bundling")
}

When it happens

Trigger: Passing an empty languages slice to i18n.New / catalog.NewCatalog — e.g. deriving languages from directory scanning or config that matched no files.

Common situations: Translation directory empty or wrong path so language detection yields zero languages; config file missing the languages key; glob pattern with no matches; environments where locales were not bundled in the container image.

Related errors

• nil loader
• expected language index to be lower or equal than %d but got
• auth: configuration: %s access token is missing from the con
• %w: example: %s
• parse yaml: %w

AI-assisted analysis of kataras/iris@7bedaf55a0 (2026-08-30). Data as JSON: /api/errors/b3a1c5ecc82cb8b6. Report an issue: GitHub.