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joi

Conditional validation with Joi

I try to implement conditional validation with Joi. I have an endpoint that can accept either:

{
    from: 'abc'
}

Or

{
    type: 'some-type'
}

If the type field isn't present, the from field is mandatory and if the from field isn't present, the type field is mandatory. The type can only accept a set of values.

I tried the following approach without success:

type: joi.alternatives().conditional('from', {
    is: joi.string().empty(), 
    then: joi.string().required().valid('val1', 'val2'),
    otherwise: joi.optional()
}).messages({
    'any.valid': 'type.not.supported.value',
    'any.required': 'type.required'
}),
from: joi.alternatives().conditional('type', {
    is: joi.string().empty(),
    then: joi.required(),
    otherwise: joi.optional() 
}).messages({
    'any.valid': 'from.not.supported.value',
    'any.required': 'from.required'
})
Solution

  • What you describe sounds like an or constraint.

    ...a relationship between keys where one of the peers is required (and more than one is allowed)

    The following schema would work:

    joi.object().keys({
  type: joi.string().valid('val1', 'val2'),
  from: joi.string()
}).or('type', 'from');