Humanizr/Humanizer · error · InvalidOperationException

Inflection quantitySelector 'exact-numeric-singleton' requir

Error message

Inflection quantitySelector 'exact-numeric-singleton' requires at least one lexeme with an authored 'one' display.

What it means

When 'quantitySelector: exact-numeric-singleton' is active, the selector picks the 'one' display category, so at least one lexeme must author a 'display.one' form. ValidateQuantitySelector throws when the selector is set but no lexeme has an authored 'one' display, because the selector would have nothing to select.

Source

Thrown at src/Humanizer.SourceGenerators/Generators/ProfileCatalogs/InflectionCatalogParsing.cs:179

                ? ExactNumericSingletonSelector
                : throw new InvalidOperationException(
                    "Inflection defines unsupported quantity selector; expected 'exact-numeric-singleton'.");
        }

        static void ValidateQuantitySelector(
            SimpleYamlMapping mapping,
            string cardinalRule,
            string? quantitySelector,
            ImmutableArray<InflectionLexemeInput> lexemes,
            ImmutableArray<InflectionRuleInput> rules)
        {
            var hasOptedLexeme = lexemes.Any(static lexeme =>
                lexeme.Display.ContainsKey("one"));
            if (quantitySelector is not null)
            {
                if (!hasOptedLexeme)
                {
                    throw new InvalidOperationException(
                        "Inflection quantitySelector 'exact-numeric-singleton' requires at least one lexeme with an authored 'one' display.");
                }

                if (rules.Any(static rule => rule.Display.ContainsKey("one")))
                {
                    throw new InvalidOperationException(
                        "Inflection quantitySelector 'exact-numeric-singleton' cannot select productive rule display.");
                }

                return;
            }

            if (!IsCategoryReachable(mapping, cardinalRule, "one") &&
                (hasOptedLexeme ||
                 rules.Any(static rule => rule.Display.ContainsKey("one"))))
            {
                throw new InvalidOperationException(
                    "Inflection display category 'one' is unreachable without quantitySelector 'exact-numeric-singleton'.");

View on GitHub (pinned to ffc2b77c0f)

Solutions

1. Add a 'display.one' block (preferred + accepted) to at least one lexeme
2. Remove the quantitySelector if the locale's cardinal rule already reaches 'one' via its CLDR rule

Example fix

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

// Given parsed lexemes and an active quantitySelector:
bool selectorSet = m.GetScalar("quantitySelector") == "exact-numeric-singleton";
bool anyOne = lexemes.Any(l => l.Forms.Display.ContainsKey("one"));
if (selectorSet && !anyOne)
    Report($"{locale}: add a lexeme display.one or drop quantitySelector.");

static bool SelectorHasOneDisplay(
    bool selectorSet, IEnumerable<Lexeme> lexemes) =>
    !selectorSet || lexemes.Any(l => l.Display.ContainsKey("one"));

When it happens

Trigger: quantitySelector is set to 'exact-numeric-singleton' but every lexeme's 'forms.display' omits the 'one' category (only 'other' or other categories are present).

Common situations: Enabling the selector on a locale whose lexemes only declare 'other'; deleting the lexeme that was the sole provider of the 'one' display; forgetting to add the 'one:' block when enabling the selector.

Related errors

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

AI-assisted analysis of Humanizr/Humanizer@ffc2b77c0f (2026-08-13). Data as JSON: /api/errors/fe553dd847f9dfcb. Report an issue: GitHub.