Function requireArrayLength

src/lib/validate.ts:195–225

(
  field: string,
  arr: unknown,
  opts: KindOpts & { min?: number; max?: number; itemNoun?: string },
)

 *                     for the max message.
 */
export function requireArrayLength(
  field: string,
  arr: unknown,
  opts: KindOpts & { min?: number; max?: number; itemNoun?: string },
): asserts arr is unknown[] {
  const { kind = 'field', min = 0, max, itemNoun = 'item' } = opts;

  // Structural check: must be an array.
  const typeResult = v.safeParse(v.array(v.unknown()), arr);
  if (!typeResult.success) {
    throw localValidationError(field, 'is required and must be an array', undefined, kind);
  }

  const arrVal = arr as unknown[];

  // Lower bound.
  if (arrVal.length < min) {
    const minLabel = min === 1 ? `one ${itemNoun}` : `${min} ${itemNoun}s`;
    throw localValidationError(field, `must contain at least ${minLabel}`, undefined, kind);
  }

  // Upper bound.
  if (max !== undefined && arrVal.length > max) {
    throw localValidationError(
      field,
      `must contain at most ${max} ${itemNoun}s (got ${arrVal.length})`,
      undefined,
      kind,
    );
  }
}