joi-to-json

Objective

I have been using joi a lot in different Node.js projects to guard the API. It's The most powerful schema description language and data validator for JavaScript. as it said.

Many times, we need to utilize this schema description to produce other output, such as Swagger OpenAPI doc. That is why I build joi-route-to-swagger in the first place.

At the beginning, joi-route-to-swagger relies on joi-to-json-schema which utilizes many joi internal api or properties. I believed there was reason. Maybe joi did not provide the describe api way before. But I always feel uncomfortable and think it's time to move on.

The intention of joi-to-json is to support converting different version's joi schema to JSON Schema using describe api.

2.0.0 is out

It's a breaking change.

• Functionally, output format supports OpenAPI Schema other than purely JSON Schema.

• Technically, implementation theory has a big change:

  • In v1.0.0, it directly converts joi.describe() to JSON schema using different parser implementations.
  • In v2.0.0, joi.describe() of different versions are first converted to one base format, the latest version of joi.describe() output. Then different parsers (JSON, OpenAPI) all refer to this base format.

• The benefits of the change are:

  • Easier to retire old version of joi.
  • Easier to support more output formats.

Installation

npm install joi-to-json

Joi Version Support

• @commercial/joi
  • v12.1.0
• joi
  • 13.7.0
  • 14.3.1
• @hapi/joi
  • 15.1.1
  • 16.1.8
• joi
  • 17.4.2

For all above versions, I have tested one complex joi object fixtures which covers most of the JSON schema attributes that can be described in joi schema.

Although the versions chosen are the latest one for each major version, I believe it should be supporting other minor version as well.

Usage

Only one API parse is available. It's signature is parse(joiObj, type = 'json')

Currently supported output types:

• json - Default. Stands for JSON Schema Draft 07
• open-api - Stands for OpenAPI Schema
• json-draft-04 - Stands for JSON Schema Draft 04
• json-draft-2019-09 - Stands for JSON Schema Draft 2019-09

The output schema format are in outputs under specific folders for different types.

Sample code is as below:

const parse = require('joi-to-json')

const joiSchema = joi.object().keys({
  nickName: joi.string().required().min(3).max(20).example('鹄思乱想').description('Hero Nickname')
    .regex(/^[a-z]+$/, { name: 'alpha', invert: true }),
  avatar: joi.string().required().uri(),
  email: joi.string().email(),
  ip: joi.string().ip({ version: ['ipv4', 'ipv6'] }),
  hostname: joi.string().hostname().insensitive(),
  gender: joi.string().valid('Male', 'Female', '').default('Male'),
  height: joi.number().precision(2).positive().greater(0).less(200),
  birthday: joi.date().iso(),
  birthTime: joi.date().timestamp('unix'),
  skills: joi.array().items(joi.alternatives().try(
    joi.string(),
    joi.object().keys({
      name: joi.string().example('teleport').alphanum().lowercase().required().description('Skill Name'),
      level: joi.number().integer().min(10).max(100).default(50).multiple(10).example(10).description('Skill Level')
    })
  ).required()).min(1).max(3).unique().description('Skills'),
  tags: joi.array().items(joi.string().required()).length(2),
  retired: joi.boolean().truthy('yes').falsy('no').insensitive(false),
  certificate: joi.binary().encoding('base64'),
  notes: joi.any().meta({ 'x-supported-lang': ['zh-CN', 'en-US'], deprecated: true })
})

const jsonSchema = parse(joiSchema)
// Or parsing to OpenAPI schema through:
// const openApiSchema = parse(joiSchema, 'open-api')

Joi to OpenAPI

Most Joi specifications result in the expected OpenAPI schema.

E.g.,

const joi = require('joi')
const { dump } = require('js-yaml')
const { writeFile } = require('fs/promises')

const joiSchema = joi.object().keys({
  uuid: joi.string().uuid({ version: ['uuidv3', 'uuidv5'] }),
  nickName: joi.string().required().example('鹄思乱想').description('Hero Nickname').min(3).max(20).pattern(/^[a-z]+$/, { name: 'alpha', invert: true }),
  avatar: joi.string().required().uri(),
  email: joi.string().email(),
  ip: joi.string().ip({ version: ['ipv4', 'ipv6'] }),
  hostname: joi.string().hostname().insensitive(),
  gender: joi.string().valid('Male', 'Female', '', null).default('Male'),
  isoDateString: joi.string().isoDate(),
  isoDurationString: joi.string().isoDuration(),
  birthday: joi.date().iso(),
  certificate: joi.binary().encoding('base64'),
  tags: joi.array().items(joi.string().required()).length(2),
  nested: joi.object().keys({
    key: joi.string()
  }).unknown(true)
}).unknown(false)

async function writeYAML(targetPath) {
  const openApiSchema = parse(joiSchema, 'open-api')

  const openApiSchemaYAML = dump(openApiSchema, {lineWidth: 120, noCompatMode: true})
  await writeFile(targetPath, openApiSchemaYAML)
}

results in

type: object
required:
  - nickName
  - avatar
properties:
  uuid:
    type: string
    format: uuid
  nickName:
    description: Hero Nickname
    type: string
    pattern: ^[a-z]+$
    minLength: 3,
    maxLength: 20,
    example: 鹄思乱想
  avatar:
    type: string
    format: uri
  email:
    type: string
    format: email
  ip:
    type: string
    oneOf:
      - format: ipv4
      - format: ipv6
  hostname:
    type: string
    format: hostname
  gender:
    type: string
    default: Male
    enum:
      - Male
      - Female
      - ''
      - null
    nullable: true
  isoDateString:
    type: string
    format: date-time
  isoDurationString:
    type: string
    format: duration
  birthday:
    type: string
    format: date-time
  certificate:
    type: string
    format: binary
  tags:
    type: array
    items:
      type: string
    minItems: 2
    maxItems: 2
  nested:
    type: object
    properties:
      key:
        type: string
    additionalProperties: true    
additionalProperties: false

Some OpenAPI features are not supported directly in Joi, but Joi schemas can be annotated with joi.any().meta({…}) to get them in the OpenAPI schema:

…

const joiSchema = joi.object().keys({
  deprecatedProperty: joi.string().meta({ deprecated: true }).required(),
  readOnlyProperty: joi.string().meta({ readOnly: true }),
  writeOnlyProperty: joi.string().meta({ writeOnly: true }),
  xMeta: joi.string().meta({ 'x-meta': 42 }),
  unknownMetaProperty: joi.string().meta({ unknownMeta: 42 })
}).unknown(true)

…

begets:

type: object
required:
  - deprecatedProperty
properties:
  deprecatedProperty:
    type: string
    deprecated: true
  readOnlyProperty:
    type: string
    readOnly: true
  writeOnlyProperty:
    type: string
    writeOnly: true
  xMeta:
    type: string
    x-meta: 42
  unknownMetaProperty:
    type: string
    # unknownMeta is not exported
additionalProperties: true

Special Joi Operator Support

• Logical Relation Operator

Browser support

For generating JSON Schema in a browser you should use below import syntax for joi library in order to work because the joi browser minimized build does not have describe api which the joi-to-json relies on.

  import Joi from 'joi/lib/index';

TypeScript support

import joi from 'joi';
import * as Joi2Json from 'joi-to-json';
import parse from 'joi-to-json';

const logicalOpParser: Joi2Json.LogicalOpParserOpts = {
  with: function (a) {}
};

parse(joi.string()); // Default call
parse(joi.string(), 'json', {}, false); // Completely disable Logical Relation Operator
parse(joi.string(), 'open-api', {}, { logicalOpParser }); // Partially override Logical Relation Operator

Test

npm run test

You can optionally set below environment variables:

• CASE_PATTERN=joi-obj-17 to control which version of joi obj to test

Known Limitation

• For object.pattern usage in Joi, pattern parameter can only be a regular expression now as I cannot convert Joi object to regex yet.

Updates

Version 2.3.0

• Supports named link for schema resuse, such as .link('#person'). For open-api conversion, as the shared schemas are located in #/components/schemas which is not self-contained, the conversion result contains an extra schemas field so that you can extract it when required.

License

MIT