@koa-lite/joi-schema

joi-to-json-schema

The goal is to provide best effort conversion from Joi objects to JSON Schema (draft-04) with the understanding that only some of Joi's schematics can be converted directly. Primarily this module exists to convert Joi schema objects for existing tools which happen to currently consume JSON Schema.

Installation

npm install @yeongjet/joi-to-json-schema

Usage

var joi = require('joi'),
    convert = require('joi-to-json-schema'),
    joiSchema = joi.object({
      'name': joi.string().required().regex(/^\w+$/),
      'description': joi.string().optional().default('no description provided'),
      'a': joi.boolean().required().default(false),
      'b': joi.alternatives().when('a', {
        is: true,
        then: joi.string().default('a is true'),
        otherwise: joi.number().default(0)
      })
    });

convert(joiSchema);

which will produce:

{ type: 'object',
  properties: 
   { name: { type: 'string', pattern: '^\\w+$' },
     description: { default: 'no description provided', type: 'string' },
     a: { type: 'boolean', default: false },
     b: { oneOf: [ { default: 'a is true', type: 'string' }, { type: 'number', default: 0 } ] } },
  additionalProperties: false,
  required: [ 'name', 'a' ] }

JSDOC

 /**
  * Converts the supplied joi validation object into a JSON schema object,
  * optionally applying a transformation.
  *
  * @param {JoiValidation} joi
  * @param {TransformFunction} [transformer=null]
  * @returns {JSONSchema}
  */
 export default function convert(joi,transformer=null) {
   // ...
 };

 /**
  * Joi Validation Object
  * @typedef {object} JoiValidation
  */

 /**
  * Transformation Function - applied just before `convert()` returns and called as `function(object):object`
  * @typedef {function} TransformFunction
  */

 /**
  * JSON Schema Object
  * @typedef {object} JSONSchema
  */

Notes

Joi's conditional form, i.e. .when('name',{is:cond,then:joi,otherwise:joi}), is evaluated at runtime and since, from the perspective of the schema, there is no way of knowing what the condition might resolve to, this module takes the position that it should provide all possible resolutions in a JSON Schema oneOf:[] clause.

Testing

All tests cases are first checked against expected results and then validated using Kris Zyp's excellent json-schema

References

• JSON Schema - Draft 4 from json-schema.org
• IETF Draft: JSON Schema: core definitions and terminology - draft-zyp-json-schema-04
• Understanding JSON Schema(pdf)

LICENSE

Copyright 2014, Mozilla Foundation

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.