Joi nested when

Question

const schema = {
    a: Joi.any(),
    b: Joi
      .boolean()
      .default(false),
    c: Joi
      .boolean()
      .default(false)
}

How can I fix the abovementioned Joi schema to matches the following rules

• One of b or c can be true at the same time
• When b or c is true, a is forbidden otherwise a is required

Answer 1

Joi.object( {
  a: Joi
      .boolean()
      .default(false),
  b: Joi
      .boolean()
      .default(false),
  c: Joi.string().when(
    'a', {
      is: false,
      then: Joi.when(
        'b', {
          is: false,
          then: Joi.string().required()
        }
      )
    }
  ),
})

I tried nested when before asking question, but it not working before because of the order of rules

Joi.object( {
  c: Joi.string().when(
    'a', {
      is: false,
      then: Joi.when(
        'b', {
          is: false,
          then: Joi.string().required()
        }
      )
    }
  ),
  a: Joi
      .boolean()
      .default(false),
  b: Joi
      .boolean()
      .default(false),
})

the default value in the second schema is not set when the when is checking, So If you validate an empty object {}, the first schema has Validation Error: "c" is required error while the second Passed with {a: false, b: false}

I opened an issue here https://github.com/sideway/joi/issues/2683