Utility to add conditional fields to react hook forms and Zod resolvers

form-extensions.tsx

type Rule<T> = {
  field: keyof T;
  operator: 'is' | 'isNot';
  value: T[keyof T];
};

type Condition<T> = {
  type: 'show' | 'hide';
  rulesMatch: 'any' | 'all';
  rules: Rule<T>[];
};
type ConditionsType<T> = Record<keyof T, Condition<T>>
export type Conditions<T> = Partial<Record<keyof T, Condition<T>>>

export function resolveKeysToOmit<T>(data: Partial<T>, conditions: Conditions<T>) {
  const keys: (keyof T)[] = []
  if (!conditions) return keys
  // https://alexharri.com/blog/typescript-structural-typing
  Object.entries<Condition<T>>(conditions as ConditionsType<T>).forEach(([key, condition]) => {
    if (!condition) return;

    const isMatched = condition.rulesMatch === 'all'
      ? condition.rules.every((r) => {
        const value = data[r.field];
        return (
          (r.operator === 'is' && value === r.value) ||
          (r.operator === 'isNot' && value !== r.value)
        );
      })
      : condition.rules.some((r) => {
        const value = data[r.field];
        return (
          (r.operator === 'is' && value === r.value) ||
          (r.operator === 'isNot' && value !== r.value)
        );
      });

    if ((condition.type === 'show' && !isMatched) || (condition.type === 'hide' && isMatched)) {
      keys.push(key as keyof T);
    }
  })
  return keys
}