Function serializeDates

api/vitest.utils.ts:286–319

(data: T)

 * Recursively finds and converts Date objects to ISO strings while preserving shape.
 */
export function serializeDates<T>(data: T): ReplaceDates<T> {
  if (data === null || data === undefined) {
    return data as ReplaceDates<T>;
  }

  // Preserve Vitest/Jest asymmetric matchers (e.g., expect.any(Number))
  if (
    typeof data === 'object' &&
    data !== null &&
    typeof (data as { asymmetricMatch?: unknown }).asymmetricMatch ===
      'function'
  ) {
    return data as unknown as ReplaceDates<T>;
  }

  if (data instanceof Date) {
    return data.toISOString() as ReplaceDates<T>;
  }

  if (Array.isArray(data)) {
    return (data as unknown[]).map(item =>
      serializeDates(item)
    ) as ReplaceDates<T>;
  }

  if (typeof data === 'object') {
    const entries = Object.entries(data as Record<string, unknown>).map(
      ([key, value]) => [key, serializeDates(value)] as const
    );
    return Object.fromEntries(entries) as ReplaceDates<T>;
  }

  return data as ReplaceDates<T>;
}