Custom messages

The validate method accepts the custom messages alongside the validation schema object. You can define messages just for the validation rules, or you can specify them for individual fields as well.

await request.validate({
  schema: schema.create({
    // ...
  }),
  messages: {
    required: 'The {{ field }} is required to create a new account',
    'username.unique': 'Username not available'
  }
})

• The custom message for the required rule will be used by all the fields that fail the required validation.
• The username.unique combination applies only to the username field for the unique validation rule.

Messages for nested objects and arrays can be defined using the dot separator.

{
  messages: {
    'user.username.required': 'Missing value for username',
    'tags.*.number': 'Tags must be an array of numbers',
    'products.*.title.required': 'Each product must have a title'
  }  
}

Dynamic placeholders

You can make use of the following placeholders to reference runtime values inside your custom messages.

{
  messages: {
    required: '{{ field }} is required to sign up',
    enum: 'The value of {{ field }} must be in {{ options.choices }}'
  }
}

Wildcard callback

You can also define a callback function to construct the message at runtime. The callback can only be defined as a fallback using the wildcard * expression.

The callback will be invoked for all the fields in the following example, except for the username field only when it fails the required validation.

{
  messages: {
    '*': (field, rule, arrayExpressionPointer, options) => {
      return `${rule} validation error on ${field}`
    },
    'username.required': 'Username is required to sign up',
  }
}

Options passed to the message string

Following is the list of options passed by the different validation methods to the message string.

date

The date validation rule will pass the options.format.

{
  'date.format': '{{ field }} must be formatted as {{ options.format }}',
}

distinct

The distinct validation rule will pass the field on which the distinct rule is applied, along with the index at which the duplicate value was found.

{
  'products.distinct': 'The product at {{ options.index + 1 }} position has already been added earlier'
}

enum / enumSet

The enum and enumSet validation rules will pass an array of options.choices.

{
  'enum': 'The value must be one of {{ options.choices }}',
  'enumSet': 'The values must be one of {{ options.choices }}',
}

file

The file validation allows defining custom messages for the sub-rules. For example:

{
  'file.size': 'The file size must be under {{ options.size }}',
  'file.extname': 'The file must have one of {{ options.extnames }} extension names',
}

minLength / maxLength

The minLength and maxLength validation rules will pass the following options to custom messages.

{
  'minLength': 'The array must have minimum of {{ options.minLength }} items',
  'maxLength': 'The array can contain maximum of {{ options.maxLength }} items',
}

range

The range validation rule passes the start and the stop options to custom messages.

{
  'range': 'Candidate age must be between {{ options.start }} and {{ options.stop }} years',
}

requiredIfExists / requiredIfNotExists

The requiredIfExists and requiredIfNotExists validation rules will pass the options.otherField as a string.

{
  'requiredIfExists': '{{ options.otherField }} requires {{ field }}',
}

Conditional required rules

The following requiredIf* rules will pass the options.otherFields as an array of strings.

• requiredIfExistsAll
• requiredIfExistsAny
• requiredIfNotExistsAll
• requiredIfNotExistsAny

{
  'requiredIfExistsAll': '{{ options.otherFields }} requires {{ field }}',
}

requiredWhen

The requiredWhen validation rule will pass the following options.

• options.otherField
• options.operator
• options.values

{
  'requiredWhen': '{{ field }} is required when {{ otherField }}{{ operator }}{{ values }}'
}

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