How to define "at least one property required"?

[davideroffo]

Good evening, everyone 🌆
I have a question regarding fastify schemas using @sinclair/typebox:
I'm trying to create a schema where my endpoint triggers a validation error if none of the possible body parameters are passed.
Consider the following example:

const Schema = Type.Partial(
  Type.Object({
    a: Type.String(),
    b: Type.String(),
    c: Type.String()
  })
);

Basically, I want to ensure that at least one of the parameters a, b, or c is required. How can I achieve this?
Thank you 🙏

[sinclairzx81]

@davideroffo Hi,

Try minProperties: 1

const Schema = Type.Partial(
  Type.Object({
    a: Type.String(),
    b: Type.String(),
    c: Type.String()
  })
, { minProperties: 1 })

// tests
//
import { Value } from '@sinclair/typebox/value'

Value.Check(Schema, { a: '', b: '', c: '' }) // true
Value.Check(Schema, { a: '', b: '' })        // true
Value.Check(Schema, { a: '' })               // true
Value.Check(Schema, { b: '' })               // true
Value.Check(Schema, { c: '' })               // true
Value.Check(Schema, {})                      // false

[davideroffo]

Thanks a lot for your quick reply.
I just tried, but the problem is that if I pass a d parameter is not throwing any validation error:

const Schema = Type.Partial(
  Type.Object({
    a: Type.String(),
    b: Type.String(),
    c: Type.String()
  })
, { minProperties: 1 })

Value.Check(Schema, { d: '' })               // true

I want it to raise a validation error even if I'm passing properties that shouldn't be passed.

[davideroffo]

I solved it by using minProperties: 1 in conjunction with additionalProperties: false, following this Stack Overflow answer: https://stackoverflow.com/a/75233932/5830331 .

const server = Fastify({
  ajv: {
    customOptions: {
      removeAdditional: false
    }
  }
})

const Schema = Type.Partial(
  Type.Object({
    a: Type.String(),
    b: Type.String(),
    c: Type.String()
  })
, { minProperties: 1, additionalProperties: false })

Value.Check(Schema, { d: '' })               // false