I have a form that uses a pattern to validate because some of the keys can be years that change and have any number.

An example of the JSON:

{ 
 yearCosts: {
   2022: {
     other: 40
   },
   2023: {
     other: 60
   }
 },
 yearJustify: {
   years: {
     2022: {
       otherSources: 'Why we need this money this year.'
     },
     2023: {
       otherSources: 'Why we need this money this year.'
     }
   }
 }
}

It is possible to have no costs for a year. If so, then one does not need to provide justification (and therefore no need for validation). However, if there is a cost, then there needs to be justification.

I have been able to get the following to be able to validate in the Joi Sandbox:

Joi.object({
  costAllocation: Joi.object().pattern(
    /\d{4}/,
    Joi.object({
      other: Joi.number().positive().allow(0).required().messages({
        'number.base':
          'Provide a number of hours greater than or equal to 0.',
        'number.positive':
          'Provide a number of hours greater than or equal to 0.',
        'number.allow':
          'Provide a number of hours greater than or equal to 0.',
        'number.empty':
          'Provide a number of hours greater than or equal to 0.',
        'number.format': 'Provide a valid number of hours.'
      })
    })
  ),
  costAllocationNarrative: Joi.object({
    years: Joi.object({
      2022: Joi.alternatives().conditional('....costAllocation.2022.other', {
        is: Joi.number().greater(0),
        then: Joi.object({
          otherSources: Joi.string().trim().min(1).required().messages({
            'string.base': 'Provide a description of other funding.',
            'string.empty': 'Provide a description of other funding.',
            'string.min': 'Provide a description of other funding.'
          })
        }),
        otherwise: Joi.object({
          otherSources: Joi.any()
        })
      }),
      2023: Joi.alternatives().conditional('....costAllocation.2023.other', {
        is: Joi.number().greater(0),
        then: Joi.object({
          otherSources: Joi.string().trim().min(1).required().messages({
            'string.base': 'Provide a description of other funding.',
            'string.empty': 'Provide a description of other funding.',
            'string.min': 'Provide a description of other funding.'
          })
        }),
        otherwise: Joi.object({
          otherSources: Joi.any()
        })
      })
    })
  })
})

But I cannot seem to get the second half of the validation to follow a pattern that corresponds to the correct year above.