forms

name	forms
version	1.0.0
description	Forms with React Hook Form + Zod. Use this skill whenever the user is building a form, adding a form field, writing a Zod schema for a form, creating a form hook, wiring a Server Action to a form, or handling form validation. Trigger when the user creates a new form component, asks how to validate a field, wants to handle form submission, or needs to show server-side errors. Do NOT trigger for general Zod schema questions unrelated to forms.

Forms — React Hook Form + Zod

Every form in this project MUST use React Hook Form + Zod. No exceptions.

---

Required Stack

Concern	Tool	Location
Form state & submission	React Hook Form	Custom hook
Validation schema	Zod	[entity].schema.ts
Schema → RHF bridge	@hookform/resolvers/zod	Custom hook
Error messages	validation-messages.ts	Per domain
Form submission	Server Action	actions.ts

---

File Structure (per form)

domains/[entity]/
├── [form-name].schema.ts          ← Zod schema + inferred type
├── hooks/
│   └── use-[form-name]-submit.ts  ← useForm, resolver, onSubmit
├── components/organisms/
│   └── [form-name]-form.tsx       ← purely presentational
└── actions.ts                     ← Server Action with server-side revalidation

---

1. Schema ([form-name].schema.ts)

// domains/auth/login.schema.ts
import { z } from 'zod';
import { authValidationMessages } from './validation-messages';

export const loginSchema = z.object({
  email: z.string().email(authValidationMessages.email),
  password: z.string().min(8, authValidationMessages.passwordTooShort)
});

export type LoginInput = z.infer<typeof loginSchema>;

Rules:

• One schema per file — never mix unrelated schemas
• Export both the schema constant and the inferred Input type
• Error messages from validation-messages.ts — no hardcoded strings
• Never use any or bypass .safeParse() type narrowing

---

2. Hook (use-[form-name]-submit.ts)

// domains/auth/hooks/use-login-submit.ts
'use client';
import { useForm } from 'react-hook-form';
import { zodResolver } from '@hookform/resolvers/zod';
import { loginSchema, type LoginInput } from '../login.schema';
import { loginAction } from '../actions';

export function useLoginSubmit() {
  const {
    register,
    handleSubmit,
    formState: { errors, isSubmitting },
    setError
  } = useForm<LoginInput>({
    resolver: zodResolver(loginSchema)
  });

  const onSubmit = handleSubmit(async data => {
    const result = await loginAction(data);
    if (result?.error) {
      setError('root', { message: result.error });
    }
  });

  return { register, onSubmit, errors, isSubmitting };
}

Rules:

• Always pass resolver: zodResolver(schema) to useForm
• Type useForm<SchemaInput> explicitly — never infer any
• Wrap submission with handleSubmit — never call directly
• Map server errors back via setError('root', ...)
• Never call Server Actions directly from a component

---

3. Form Component ([form-name]-form.tsx)

// domains/auth/components/organisms/login-form.tsx
'use client';
import { useLoginSubmit } from '../../hooks/use-login-submit';
import { authMessages } from '../../messages';

export function LoginForm() {
  const { register, onSubmit, errors, isSubmitting } = useLoginSubmit();

  return (
    <form onSubmit={onSubmit} className="login-form">
      <div className="login-form__field">
        <label htmlFor="email">{authMessages.login.emailLabel}</label>
        <input id="email" type="email" {...register('email')} />
        {errors.email && (
          <span className="login-form__error">{errors.email.message}</span>
        )}
      </div>

      <div className="login-form__field">
        <label htmlFor="password">{authMessages.login.passwordLabel}</label>
        <input id="password" type="password" {...register('password')} />
        {errors.password && (
          <span className="login-form__error">{errors.password.message}</span>
        )}
      </div>

      {errors.root && (
        <p className="login-form__root-error">{errors.root.message}</p>
      )}

      <button type="submit" disabled={isSubmitting}>
        {isSubmitting
          ? authMessages.login.submitting
          : authMessages.login.submit}
      </button>
    </form>
  );
}

Rules:

• Form component only renders — all logic lives in the hook
• Use {...register('fieldName')} for every input
• Always render errors.{field}.message beside each field
• Always handle errors.root for server-side errors
• Disable submit button while isSubmitting
• Never use useState to track field values — RHF owns state
• Never use e.preventDefault() — handleSubmit does it

---

4. Server Action (actions.ts)

// domains/auth/actions.ts
'use server';
import { loginSchema, type LoginInput } from './login.schema';

export async function loginAction(input: LoginInput) {
  const validated = loginSchema.safeParse(input);
  if (!validated.success) {
    return { error: 'Invalid input' };
  }

  const { email, password } = validated.data;
  // ... business logic
}

Rules:

• Always revalidate on the server with schema.safeParse() — never trust client validation alone
• Return { error: string } for errors the hook can pass to setError('root', ...)

---

Multi-Step Forms

Split by step. Compose with .merge() for server validation.

// step schemas stay independent
export const step1Schema = z.object({
  firstName: z.string().min(1),
  lastName: z.string().min(1)
});
export const step2Schema = z.object({
  role: z.enum(['admin', 'member']),
  team: z.string().min(1)
});

// composed for server-side full validation
export const onboardingSchema = step1Schema.merge(step2Schema);
export type OnboardingInput = z.infer<typeof onboardingSchema>;

---

Anti-Patterns

// ❌ useState for form fields
const [email, setEmail] = useState('');

// ❌ Manual validation without Zod
if (!email.includes('@')) { setError('Invalid email'); }

// ❌ Inline schema in component
const schema = z.object({ email: z.string() }); // must be in .schema.ts

// ❌ Server Action directly in JSX for complex forms
<form action={loginAction}>

// ❌ useForm without resolver
useForm(); // validation won't run

// ❌ Hardcoded error messages in schema
z.string().email('Please enter a valid email') // must be in validation-messages.ts

---

Pre-Submit Checklist

• Schema in {name}.schema.ts with exported type
• Validation messages in validation-messages.ts
• useForm<InputType>({ resolver: zodResolver(schema) }) in the hook
• Server Action revalidates with schema.safeParse(input)
• errors.root handled for server errors
• Submit button disabled during isSubmitting
• All field errors rendered beside each input