Name: alonso-skills/joi
Rating: 100 (1 reviews)
Author: alonso-skills

alonso-skills/joi

Use when building joi schemas, validating input data, defining custom types, conditional validation with .when(), cross-field references, custom error messages, or writing joi extensions. Standalone package that integrates with the @hapi ecosystem.

100

Quality

100%

Does it follow best practices?

Impact

Pending

No eval scenarios have been run

Securityby

Passed

No known issues

Error Handling

ValidationError structure

const { error } = schema.validate(value);

error.message;    // Human-readable summary
error.details;    // Array of error detail objects
error.annotate(); // Annotated version of the input

Each detail object:

{
    message: '"name" is required',
    path: ['user', 'name'],          // Key path to the error
    type: 'any.required',            // Error code
    context: {
        label: 'user.name',          // Auto-generated label
        key: 'name',                 // Immediate key
        value: undefined             // The failing value
    }
}

`Joi.isError(err)`

Returns true if the error is a joi ValidationError.

`Joi.ValidationError`

The ValidationError constructor. Useful for instanceof checks.

Customizing error messages

`.messages(messages)` - Override specific error codes

Joi.string().min(3).max(30).messages({
    'string.base': '{{#label}} must be text',
    'string.min': '{{#label}} must be at least {{#limit}} characters',
    'string.max': '{{#label}} cannot exceed {{#limit}} characters',
    'any.required': '{{#label}} is required'
});

`.message(message)` - Override for last rule only

Joi.string().min(3).message('Too short').max(30).message('Too long');

`.label(name)` - Set the field label

Joi.string().label('Username').required();
// Error: "Username" is required

`.error(err)` - Completely override the error

// Static error
Joi.string().error(new Error('Invalid input'));

// Dynamic error
Joi.string().error((errors) => {
    return new Error(`Got ${errors.length} validation errors`);
});

Error message template variables

Available in .messages() templates:

Variable	Description
`#label`	Field label (auto or from `.label()`)
`#value`	The failing value
`#key`	The immediate object key
`#limit`	Rule argument (min, max, length)
`#type`	Expected type
`#name`	Rule name
`#regex`	Pattern source
`#valids`	List of allowed values
`#invalids`	List of denied values
`#encoding`	String encoding

Error codes by type

Common error codes:

Code	When
`any.required`	Required field missing
`any.unknown`	Unknown key in object
`any.invalid`	Value in `.invalid()` list
`any.only`	Value not in `.valid()` list
`string.base`	Not a string
`string.empty`	Empty string
`string.min`	Below minimum length
`string.max`	Above maximum length
`string.email`	Invalid email
`string.pattern.base`	Regex mismatch
`number.base`	Not a number
`number.min`	Below minimum
`number.max`	Above maximum
`number.integer`	Not an integer
`date.base`	Not a valid date
`object.base`	Not an object
`object.unknown`	Unknown key
`array.base`	Not an array
`array.min`	Below minimum items
`array.includesRequiredUnknowns`	Missing required item type

`.warning(code, [context])`

Emit a warning instead of an error. Warnings are collected but don't fail validation:

const schema = Joi.string().warning('custom.deprecation', { alt: 'newField' });

const { value, warning } = schema.validate('test', { warnings: true });
// warning.details[0].type === 'custom.deprecation'

`error.annotate([stripColors])`

Returns a string with the input annotated with error markers. Useful for debugging:

const { error } = Joi.object({
    a: Joi.number()
}).validate({ a: 'not a number' });

console.log(error.annotate());
// {
//   "a" [1]: "not a number"
// }
//
// [1] "a" must be a number