What causes "key: %q: no registered plurals for " in kataras/iris?

Register the missing plural form(s) for the key — ensure "other" is always defined as a fallback.

key: %q: no registered plurals for <%d>

Error message

key: %q: no registered plurals for <%d>

What it means

When rendering a plural Message, the library finds the plural count from the first argument and searches m.Plurals for a registered PluralForm whose rules match that count. If none matches, Render returns "key: %q: no registered plurals for <%d>". This means the count is valid but no plural form was registered that covers it.

Source

Thrown at i18n/internal/message.go:73

// Render completes the Renderer interface.
// It accepts arguments, which can resolve the pluralization type of the message
// and its variables. If the Message is wrapped by a Template then the
// first argument should be a map. The map key resolves to the pluralization
// of the message is the "PluralCount". And for variables the user
// should set a message key which looks like: %VAR_NAME%Count, e.g. "DogsCount"
// to set plural count for the "Dogs" variable, case-sensitive.
func (m *Message) Render(args ...any) (string, error) {
	if m.Plural {
		if len(args) > 0 {
			if pluralCount, ok := findPluralCount(args[0]); ok {
				for _, plural := range m.Plurals {
					if plural.Form.MatchPlural(pluralCount) {
						return plural.Renderer.Render(args...)
					}
				}

				return "", fmt.Errorf("key: %q: no registered plurals for <%d>", m.Key, pluralCount)
			}
		}

		return "", fmt.Errorf("key: %q: missing plural count argument", m.Key)
	}

	return m.Locale.Printer.Sprintf(m.Key, args...), nil
}

View on GitHub (pinned to 7bedaf55a0)

Solutions

Register the missing plural form(s) for the key — ensure "other" is always defined as a fallback.
Verify the language's CLDR plural categories and add all required forms (e.g. few/many for ru, zero/one/two/few/many for ar).
Check findPluralCount behavior: pass the count as the first Render argument as a plain number.
Provide a DefaultMessageFunc to fall back to the default language message when a form is missing.

Example fix

// before (en-US style forms on ru locale)
"apples": "one:%d яблоко|other:%d яблок"
// after
"apples": "one:%d яблоко|few:%d яблока|many:%d яблок|other:%d яблока"

Defensive patterns

Strategy: fallback

Validate before calling

// ensure counts you will render are covered
for _, n := range []int{0, 1, 2, 5, 100, 1000} {
    if _, err := msg.Render(n); err != nil {
        log.Printf("key %s uncovered for count %d: %v", key, n, err)
    }
}

Try / catch

s, err := tr.Render(n)
if err != nil && strings.Contains(err.Error(), "no registered plurals") {
    s, err = tr.Render(1) // fallback to a covered form
}

Prevention

Always define the "other" plural form as a catch-all.
For Slavic/Arabic locales, register all CLDR forms (few, many, zero...).
Smoke-test rendering with edge counts (0, 1, 2, large numbers).
Use DefaultMessageFunc to fall back to default language messages.

When it happens

Trigger: Calling Render/T with a plural key and a numeric count (e.g. 0, 2, 100) for which no PluralForm was registered — e.g. only "one" and "other" forms were defined but the language requires "few"/"many" (Russian, Arabic) or the count falls outside registered ranges.

Common situations: Incomplete translation files missing plural cases for a language, counts like 0 or 2 hitting unregistered forms in Slavic/Arabic locales, or custom PluralFormDecoder mismatching the registered forms.

Related errors

AI-assisted analysis of kataras/iris@7bedaf55a0 (2026-08-30). Data as JSON: /api/errors/97ad33ab14ff66f2. Report an issue: GitHub.