How to do a cross field validation?

[askareija]

Hi!, i have a question. I'm using elysia and i know that elysia using typebox for validation. I have validation code like this:

export const authRequestVerificationCodeValidation = {
  body: t.Object({
    contact: t.Union([
      t.String({ format: "email" }),
      t.String({ minLength: 8 }),
    ]),
    sendMethod: t.Union([t.Literal("email"), t.Literal("whatsapp")]),
  }),
};

Is there a way i can validate if the sendMethod field is email, then contact field validation must be t.String with email format, else if whatsapp then the validation is t.String with minLength of 8?

Thanks

[sinclairzx81]

@askareija Hi,

TypeBox doesn't have cross field validation as it's not well represented in the Json Schema specification. However you can reimplement this type in the following way to make use of TypeScript discriminated unions (which is supported in TypeBox)

TypeScript Link Here

import { Type as t, Static } from '@sinclair/typebox'

export type AuthRequestVerificationType = Static<typeof AuthRequestVerificationType>
export const AuthRequestVerificationType = t.Union([
  t.Object({ 
    sendMethod: t.Literal('email'),    // discriminator
    contact: t.String({ format: 'email' })
  }),
  t.Object({ 
    sendMethod: t.Literal('whatsapp'), // discriminator
    contact: t.String({ minLength: 8 })
  }),
])

Hope this helps S

[sinclairzx81]

Just as follow on addendum, for your particular case, the specification does support conditional schematics which would work for your particular use case...

import { Type, Static } from '@sinclair/typebox'

export const T = Type.Object({
    x: Type.Union([
        Type.Literal(1),
        Type.Literal(2),
    ]),
}, {
    if: Type.Object({ x: Type.Literal(1) }),
    then: Type.Object({ y: Type.Literal(3) })
})

// if x === 1 expect { x: 1, y: '...' }
// if x === 2 expect { x: 2 }

However the TypeBox compiler infrastructure doesn't currently support these kind of schematics as there are difficulties reconciling the appropriate static type (although the above schematic is supported in Ajv and other standard validators). As Elysia is backed by the TypeBox TypeCompiler, the recommendation is to use the Discriminated Union type above.

Cheers S

[askareija]

Ah i see, thanks! i'll try this