zod-4

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• SKILL.md

SKILL.md (first lines)

## Breaking Changes from Zod 3

```typescript
// ❌ Zod 3 (OLD)
z.string().email()
z.string().uuid()
z.string().url()
z.string().nonempty()
z.object({ name: z.string() }).required_error('Required')

// ✅ Zod 4 (NEW)
z.email()
z.uuid()
z.url()
z.string().min(1)
z.object({ name: z.string() }, { error: 'Required' })
```

## Basic Schemas

```typescript
import { z } from 'zod'

// Primitives
const stringSchema = z.string()
const numberSchema = z.number()
const booleanSchema = z.boolean()
const dateSchema = z.date()

// Top-level validators (Zod 4)
const emailSchema = z.email()
const uuidSchema = z.uuid()
const urlSchema = z.url()

// With constraints
const nameSchema = z.string().min(1).max(100)
const ageSchema = z.number().int().positive().max(150)
const priceSchema = z.number().min(0).multipleOf(0.01)
```

## Object Schemas

```typescript
const userSchema = z.object({
  id: z.uuid(),
  email: z.email({ error: 'Invalid email address' }),
  name: z.string().min(1, { error: 'Name is required' }),
  age: z.number().int().positive().optional(),
  role: z.enum(['admin', 'user', 'guest']),
  metadata: z.record(z.string(), z.unknown()).optional(),
})

type User = z.infer<typeof userSchema>

// Parsing
const user = userSchema.parse(data) // Throws on error
const result = userSchema.safeParse(data) // Returns { success, data/error }

if (result.success) {
  console.log(result.data)
} else {
  console.log(result.error.issues)
}
```

## Arrays and Records

```typescript
// Arrays
const tagsSchema = z.array(z.string()).min(1).max(10)
const numbersSchema = z.array(z.number()).nonempty()

// Records (objects with dynamic keys)
const scoresSchema = z.record(z.string(), z.number())
// { [key: string]: number }

// Tuples
const coordinatesSchema = z.tuple([z.number(), z.number()])
// [number, number]
```

## Unions and Discriminated Unions

```typescript
// Simple union
const stringOrNumber = z.union([z.string(), z.number()])

// Discriminated union (more efficient)
const resultSchema = z.discriminatedUnion('status', [
  z.object({ status: z.literal('success'), data: z.unknown() }),
  z.object({ status: z.literal('error'), error: z.string() }),
])
```

## Transformations

```typescript
// Transform during parsing
const lowercaseEmail = z.email().transform((email) => email.toLowerCase())

// Coercion (convert types)
const numberFromString = z.coerce.number() // "42" → 42
const dateFromString = z.coerce.date() // "2024-01-01" → Date

// Preprocessing
const trimmedString = z.preprocess(
  (val) => (typeof val === 'string' ? val.trim() : val),
  z.string(),
)
```

## Refinements

```typescript
const passwordSchema = z
  .string()
  .min(8)
  .refine((val) => /[A-Z]/.test(val), {
    message: 'Must contain uppercase letter',

From vab1997/mecania-assistant, Apache-2.0.

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