Humanizr/Humanizer · error · InvalidOperationException

Locale ' ' is not defined.

Error message

Locale '{localeCode}' is not defined.

What it means

Thrown by ResolveLocale when a locale is referenced (typically via an 'inherits'/'variantOf' parent) but no locale file defines that code. Inheritance targets must exist in the catalog. Surfaced as compiler diagnostic HSG003 (severity Error).

Solutions

1. Verify the parent code in the message matches an existing file name (without extension) under src/Humanizer/Locales.
2. Correct the inherits/variantOf value to the real parent code, or add the missing parent file.
3. Check casing: locale codes are compared ordinally, so fr-FR does not match fr-fr.
4. Rebuild to confirm the HSG003 diagnostic clears.

Example fix

# before (file src/Humanizer/Locales/fr-FR.yml)
inherits: fr-CA
# after (no fr-CA.yml exists; inherit from fr instead)
inherits: fr

# Collect every inherits/variantOf target and confirm a matching file exists.
codes=$(find src/Humanizer/Locales -name '*.yml' -printf '%f\n' | sed 's/\.yml$//' | sort -u)
grep -rhoE '^(inherits|variantOf):\s*.*' src/Humanizer/Locales | awk '{print $2}' | sort -u | while read parent; do
  echo "$codes" | grep -qxF "$parent" || echo "MISSING PARENT: $parent"
done

When it happens

Trigger: A locale file sets inherits: <parent> (or variantOf) to a code that has no corresponding file, e.g. inherits: fr-FR when only fr.yml exists, or a typo like inherits: en-US.

Common situations: Author renames a parent locale without updating children; typo in the inherits value; referencing a not-yet-added locale; case mismatch between the inherits value and the file name.

Related errors

• Locale ' ' is defined more than once.
• Phrase forms ' ' must define at least one form.
• Phrase ' ' can only use placeholders: .
• Phrase ' ' can only use placeholders in explicit 'template'…
• Phrase ' ' cannot use numeric placeholder ' }'.

AI-assisted analysis of Humanizr/Humanizer@ffc2b77c0f (2026-08-13). Data as JSON: /api/errors/ea19f9896c53f341. Report an issue: GitHub.

Appendix: source

Thrown at src/Humanizer.SourceGenerators/Common/LocaleYamlCatalog.cs:452

        static LocaleDefinition ParseLocaleDefinition(string localeCode, string fileText)
        {
            var document = CanonicalLocaleAuthoring.Parse(localeCode, fileText);
            return CanonicalLocaleAuthoring.ToLocaleDefinition(document);
        }

        static ResolvedLocaleDefinition ResolveLocale(
            string localeCode,
            Dictionary<string, LocaleDefinition> parsedLocales,
            HashSet<string> resolving,
            ImmutableArray<ResolvedLocaleDefinition>.Builder cache,
            ImmutableArray<Diagnostic>.Builder diagnostics)
        {
            if (cache.FirstOrDefault(cached => cached.LocaleCode == localeCode) is { } cached)
                return cached;

            if (!parsedLocales.TryGetValue(localeCode, out var locale))
            {
                throw new InvalidOperationException($"Locale '{localeCode}' is not defined.");
            }

            if (!resolving.Add(localeCode))
            {
                throw new InvalidOperationException($"Locale inheritance cycle detected at '{localeCode}'.");
            }

            ResolvedLocaleDefinition inherited;
            if (string.IsNullOrWhiteSpace(locale.Inherits))
            {
                inherited = ResolvedLocaleDefinition.Empty(localeCode);
            }
            else
            {
                var inheritedLocale = locale.Inherits!;
                if (!parsedLocales.ContainsKey(inheritedLocale))
                {
                    diagnostics.Add(Diagnostic.Create(

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