Messages

Every constraint reports a message for people, in English by default, such as must have at least 2 characters. Change it in three places, from the broadest to the narrowest.

For the whole application

messages { } in the configuration changes the default message of a constraint everywhere. Each message is a property named after the constraint:

Validity.configure {
    messages {
        required = "é obrigatório"
        minLength = "deve ter pelo menos {min} caracteres"
        email = "deve ser um e-mail válido"
    }
}

The others keep their default. The messages reference lists all of them, with their defaults and placeholders.

For one call

The same block inside Validity { } changes them for one validation only, which is how a server answers each request in its own language:

user.validate(Validity { messages { email = "deve ser um e-mail válido" } })

For one rule

Every constraint takes a message, which replaces the default for that call:

::name required { minLength(2, message = "please type your full name") }
::email.required("we need an email to send the receipt") { email() }

Constraints that take an argument also accept a message built from the value, for a message that depends on it:

::name required { minLength(3, message = { min -> "has $length characters, needs $min" }) }

Placeholders

A message can use placeholders in braces, filled in when the violation is built:

Placeholder	Filled with	Available in
`{path}`	the path of the value, such as `shipping.zipCode`	every message
`{value}`	the value being checked	every message
`{min}`, `{max}`, `{other}`, `{pattern}`, …	the arguments of the constraint, by name	the messages of constraints that take them
`{fields}`	the properties of a presence rule	`atLeastOneOf` and the other presence rules

messages { max = "{path} is {value}, more than the maximum of {max}" }

A placeholder the message has no value for is left as it is, so a typo shows up in the message instead of failing.

The message of a constraint is not always its name

Most messages are named after their constraint, but a few constraints share a name across types and need different words. The size rules of a map count entries, not items, and the Boolean rules cannot be named isTrue:

Constraint	Message to change
`minSize`, `maxSize`, `size`, `sizeBetween` on a map	`minEntries`, `maxEntries`, `entries`, `entriesBetween`
`contains`, `notContains` on a collection	`containsElement`, `notContainsElement`
`distinctBy`	`distinct`
`between` on dates and times	`betweenDates`
`isTrue`, `isFalse`	`mustBeTrue`, `mustBeFalse`
`notNull`	`required`

The constraints reference gives the message of every constraint. The code of the violation is always the name of the constraint.

Messages of a country

The constraints of each country have their messages in a block of their own:

messages {
    brazil {
        cpf = "CPF inválido"
        cnpj = "CNPJ inválido"
    }
    spain { dni = "DNI no válido" }
}

The blocks are brazil, bulgaria, canada, france, israel, netherlands, pakistan, poland, russia, slovenia, spain, thailand, ukraine and unitedStates.

Messages of a module

A module such as validity-phone adds its own block to messages:

messages { phone { mobilePhone = "celular inválido" } }

Messages of your own constraints

Your custom constraints can have configurable messages too. Hold them in a class, declare a MessagesKey for it, and read the current messages from the key:

class ShopMessages {
    var sku: String = "must be a SKU such as ABC-1234"
}

val SHOP_MESSAGES = MessagesKey(::ShopMessages)

fun ValidationNode<String>.sku(
    message: String = SHOP_MESSAGES.current.sku
): Unit = constraint(message = message, code = "sku") { SKU_FORMAT.matches(it) }

Users then change them in the same configuration, with module:

Validity.configure { messages { module(SHOP_MESSAGES).sku = "SKU inválido" } }

MessagesKey.current reads the messages of the configuration that is validating, so Validity { } for one call works for them too.

Get started

Writing rules

Beyond the object

Reading the result

Configuration

For AI agents

For the whole application

For one call

For one rule

Placeholders

The message of a constraint is not always its name

Messages of a country

Messages of a module

Messages of your own constraints

​For the whole application

​For one call

​For one rule

​Placeholders

​The message of a constraint is not always its name

​Messages of a country

​Messages of a module

​Messages of your own constraints

For the whole application

For one call

For one rule

Placeholders

The message of a constraint is not always its name

Messages of a country

Messages of a module

Messages of your own constraints