sequelize-validate-subfields

simple framework for validating subfields of JSON attributes of Sequelize models

Introduction

If you ever use JSON attributes in Sequelize models, you'll probably want to validate that the JSON matches some schema. And if values within the JSON come from a form filled out by a user, you'll probably want to be able to show validation errors from the server associated with the correct form field on the client.

But Sequelize ValidationErrors be default only identify the top-level attribute of each validation error. For example if you have the following validator:

  address: {
    type: Sequelize.JSON,
    validate: {
      isValid(address) {
        if (/^\d{5}$/.test(address.postalCode)) throw new Error('invalid postal code')
      }
    }
  }

You'll get an error including the following information:

ValidationError {
  errors: [
    ValidationErrorItem {
      message: 'invalid postal code',
      type: 'Validation error',
      path: 'address',
      __raw: Error {
        message: 'invalid postal code',
      },
      ...
    }
  ]
}

If you use this package to perform validation, you can tag each validation error with a specific field path instead:

  address: {
    type: Sequelize.JSON,
    validate: {
      isValid: validateSubfields(function * (address) {
        if (/^\d{5}$/.test(address.postalCode)) yield {path: ['postalCode'], message: 'invalid postal code'}
        if (states.has(address.state)) yield {path: ['state'], message: 'invalid state'}
        // etc.
      })
    }
  }

And you'll get an error including those paths:

ValidationError {
  errors: [
    ValidationErrorItem {
      message: 'validation failed',
      type: 'Validation error',
      path: 'address',
      __raw: Error {
        message: 'validation failed',
        validation: {
          errors: [
            {path: ['postalCode'], message: 'invalid postal code'},
            {path: ['state'], message: 'invalid state'},
          ]
        }
      }
    }
  ]
}

This package also provides a flattenValidationErrors function to combine subfield validation errors like in the example above with normal validation errors on non-JSON fields:

;[
  { path: ['address', 'postalCode'], message: 'invalid postal code' },
  { path: ['address', 'state'], message: 'invalid state' },
]

Installation

npm install --save sequelize-validate-subfields

API

validateSubfields(validator)

const { validateSubfields } = require('sequelize-validate-subfields')

Arguments

validator: (value: any) => Iterable<FieldValidation>

a generator function which receives the attribute value and may yield as many validation FieldValidation objects as you wish, each specifying a validation error in the following form:

{
  path: Array<string | number>,
  message: string,
}

path is the lodash.get-style path within the attribute (i.e. not including the attribute name itself) that message is associated with. For example if you define an address attribute and validator on a model like this:

  address: {
    type: Sequelize.JSON,
    validate: {
      isValid: validateSubfields(function * (address) {
        if (/^\d{5}$/.test(address.postalCode)) yield {path: ['postalCode'], message: 'invalid postal code'}
        if (states.has(address.state)) yield {path: ['state'], message: 'invalid state'}
        // etc.
      })
    }
  }

Notice that the yielded paths don't contain 'address' (the name of the attribute) themselves; they must be relative to the root of the attribute, instead of the root of the model instance.

Returns: (value: any) => void

A Sequelize custom validator function that delegates to your validator function and combines any FieldValidations it yielded into the appropriate thrown error.

flattenValidationErrors(error, [options])

const { flattenValidationErrors } = require('sequelize-validate-subfields')

Arguments

error: Sequelize.ValidationError

A ValidationError hich may contain zero or more ValidationErrorItems -- some may be from non-JSON field validation errors, and some may contain FieldValidations from validateSubfields.

options?: {formatItemMessage?: (item: ValidationErrorItem) => string}

formatItemMessage allows you to override the error messages output for ValidationErrorItems that don't contain FieldValidations using your own custom function.

Returns: Array<FieldValidation>

A flattened array of FieldValidations with paths relative to the root of the model instance instead of being relative to specific attributes. For instance, if you have the following model:

const User = sequelize.define('User', {
  username: {
    type: Sequelize.STRING,
    validate: {
      notEmpty: {
        msg: 'required',
      },
    },
  },
  address: {
    type: Sequelize.JSON,
    validate: {
      isValid: validateSubfields(function* (address) {
        if (/^\d{5}$/.test(address.postalCode))
          yield { path: ['postalCode'], message: 'invalid postal code' }
        if (states.has(address.state))
          yield { path: ['state'], message: 'invalid state' }
        // etc.
      }),
    },
  },
})

And you validate the following fields:

{
  username: '',
  address: {
    postalCode: '123',
    state: 'KG',
  }
}

You will get a ValidationError with the following structure:

ValidationError {
  errors: [
    ValidationErrorItem {
      message: 'required',
      type: 'Validation error',
      path: 'username',
    },
    ValidationErrorItem {
      message: 'validation failed',
      type: 'Validation error',
      path: 'address',
      __raw: Error {
        message: 'validation failed',
        validation: {
          errors: [
            {path: ['postalCode'], message: 'invalid postal code'},
            {path: ['state'], message: 'invalid state'},
          ]
        }
      }
    }
  ]
}

Calling flattenValidationErrors on this will produce:

;[
  { path: ['username'], message: 'required' },
  { path: ['address', 'postalCode'], message: 'invalid postal code' },
  { path: ['address', 'state'], message: 'invalid state' },
]