Humanizr/Humanizer · error · InvalidOperationException

Inflection lexeme '{lexemeId}' form '{name}' preferred value

Error message

Inflection lexeme '{lexemeId}' form '{name}' preferred value must be accepted.

What it means

For each form, the 'preferred:' value must also appear in the 'accepted:' list (ordinal comparison). ParseForm throws when preferred is not a member of accepted, because the preferred form is the default and must be an accepted spelling.

Source

Thrown at src/Humanizer.SourceGenerators/Generators/ProfileCatalogs/InflectionCatalogParsing.cs:392

                    $"Inflection lexeme '{lexemeId}' form '{name}' must define preferred"),
                casing,
                ownerScripts,
                subject,
                allowStemPlaceholder: false,
                allowNonLetters: true);
            var accepted = NormalizeAuthoredTexts(
                GetRequiredStrings(
                    mapping,
                    "accepted",
                    $"Inflection lexeme '{lexemeId}' form '{name}' must define accepted"),
                casing,
                ownerScripts,
                subject,
                allowStemPlaceholder: false,
                allowNonLetters: true);
            if (!accepted.Contains(preferred, StringComparer.Ordinal))
            {
                throw new InvalidOperationException(
                    $"Inflection lexeme '{lexemeId}' form '{name}' preferred value must be accepted.");
            }

            return new(preferred, accepted);
        }

        static ImmutableArray<InflectionRuleInput> ParseRules(
            SimpleYamlMapping mapping,
            ImmutableHashSet<string> sourceIds,
            ImmutableHashSet<string> lexemeIds,
            ImmutableArray<string> ownerScripts,
            string cardinalRule,
            string casing)
        {
            if (!mapping.TryGetValue("rules", out var value))
            {
                return [];
            }

View on GitHub (pinned to ffc2b77c0f)

Solutions

1. Add the preferred value verbatim to the accepted list

Example fix

# before
            other:
              preferred: 'cats'
              accepted:
                - 'cat'
# after
            other:
              preferred: 'cats'
              accepted:
                - 'cats'

foreach (var form in allForms)
    if (!form.Accepted.Contains(form.Preferred, StringComparer.Ordinal))
        Report($"{locale}: preferred '{form.Preferred}' must appear in accepted.");

static bool PreferredIsAccepted(Form f) =>
    f.Accepted.Contains(f.Preferred, StringComparer.Ordinal);

When it happens

Trigger: 'preferred:' names a spelling that is absent from (or differs in case/spacing from) every entry in 'accepted:'.

Common situations: Editing the preferred spelling and forgetting to mirror it in the accepted list; a casing-mode change that alters preferred but not accepted.

Related errors

• Inflection defines unsupported quantity selector; expected '
• Inflection quantitySelector 'exact-numeric-singleton' requir
• Inflection quantitySelector 'exact-numeric-singleton' cannot
• Inflection display category 'one' is unreachable without qua
• Active inflection bundle must define lexemes.

AI-assisted analysis of Humanizr/Humanizer@ffc2b77c0f (2026-08-13). Data as JSON: /api/errors/77e1b4a3069d9f42. Report an issue: GitHub.