Comparing two objects in Joi validation (eg. to avoid duplicates) - joi

Question

I'm using Joi to validate a complex form entry. The form asks for two addresses, mainContactAddress and seniorContactAddress. I want to validate them to ensure they aren't the same address.
Each address is an object like this:
{
"line1": "123 Some Street",
"line2": "Some Town",
"county": "Some County",
"postcode": "123 ABC",
"townCity": "City"
}
I initially tried this:
Joi.ukAddress().invalid(Joi.ref('seniorContactAddress'))
(ukAddress() is a custom extension I've created which specifies each of the above fields as a required string.)
This doesn't work, because the equality === comparison between the two objects returns false even when they have the same string values.
I can't see a Joi method to do this. I was hoping to be able to serialise the object (eg. something like Object.values(mainContactAddress).join(',') and then compare the resulting strings) but Joi.ref() only gives, well, a reference to the object, so I can't call functions against it directly.
Any thoughts on how I could achieve this validation/comparison?

Answer 1

I ended up writing a custom rule for my extension:
{
// Enforce a unique address compared to the senior contact
name: 'mainContact',
validate(params, value, state, options) {
// Format addresses into a comparable string,
// making sure we sort them as the stored version
// is in a different order to the form-submitted one.
const serialize = address =>
Object.values(address)
.sort()
.join(',');
const seniorContactAddress = get(
state.parent,
'seniorContactAddress',
[]
);
if (serialize(seniorContactAddress) === serialize(value)) {
return this.createError(
'address.matchesSenior',
{ v: value },
state,
options
);
} else {
return value;
}
}
}
This does feel like an anti-pattern (eg. abusing state to look at other values in the Joi object) but it does what I needed.