sickn33/agentic-awesome-skills · warning · Error

Age must be positive

Error message

Age must be positive

What it means

Thrown by the throw-based validateUser example in fp-pragmatic when `age` is a number but is negative. It represents a range/semantic check layered after the type check, and the skill contrasts it with an Either pipeline that surfaces the same failure without exceptions.

Solutions

1. Clamp or reject negative values at the input layer (min='0' on numeric inputs)
2. Validate with a boundary-aware schema (zod .nonnegative() / io-ts brand) before business logic
3. Return the error via Either/Result instead of throwing, as the skill's 'After' version does

Example fix

// before
if (obj.age < 0) throw new Error('Age must be positive')

// after
const ageCheck = (obj: Record<string, unknown>) =>
  typeof obj.age === 'number' && obj.age >= 0
    ? E.right(obj as User)
    : E.left('Age must be positive')

const isValidAge = (a: unknown) => typeof a === 'number' && Number.isFinite(a) && a >= 0

const hasNonNegativeAge = (x: unknown): x is { age: number } =>
  typeof x === 'object' && x !== null && typeof (x as any).age === 'number' && (x as any).age >= 0

When it happens

Trigger: Calling validateUser with an object whose email is valid and age is a negative number, e.g. { email: 'a@b.c', age: -1 }.

Common situations: Test fixtures with sentinel values like -1; arithmetic that computes age from dates with an inverted subtraction; free-text numeric fields accepting minus signs.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Age must be a number
• Age required
• Data must be an object
• ID required
• ID required

AI-assisted analysis of sickn33/agentic-awesome-skills@58d857988f (2026-08-26). Data as JSON: /api/errors/0e87f27908e29d28. Report an issue: GitHub.

Appendix: source

Thrown at skills/fp-pragmatic/SKILL.md:470

  getManagerEmail(employee),
  O.fold(
    () => sendToDefault(),
    (email) => sendTo(email)
  )
)
```

### Validation with Multiple Checks

```typescript
// Before: Throws on first error
function validateUser(data: unknown): User {
  if (!data || typeof data !== 'object') throw new Error('Must be object')
  const obj = data as Record<string, unknown>
  if (typeof obj.email !== 'string') throw new Error('Email required')
  if (!obj.email.includes('@')) throw new Error('Invalid email')
  if (typeof obj.age !== 'number') throw new Error('Age required')
  if (obj.age < 0) throw new Error('Age must be positive')
  return obj as User
}

// After: Returns first error, type-safe
const validateUser = (data: unknown): E.Either<string, User> =>
  pipe(
    E.Do,
    E.bind('obj', () =>
      typeof data === 'object' && data !== null
        ? E.right(data as Record<string, unknown>)
        : E.left('Must be object')
    ),
    E.bind('email', ({ obj }) =>
      typeof obj.email === 'string' && obj.email.includes('@')
        ? E.right(obj.email)
        : E.left('Valid email required')
    ),
    E.bind('age', ({ obj }) =>

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