Schematized

Turn objects into JSON schemas! The more examples you provide, the better your schema will be.

A Node port of the Python module GenSON but with more inferred constraints.

Example use case: Generate JSON schemas using your API tests, then use the schemas to validate. To keep up to date, Write a test that compares your current schema with the generated schema. Then when your API changes, just update the tests with the newly generated schemas and move on with your day.

Schematized

🚀 Quick start

Add dependency

yarn add schematized

Basic usage : See output

import SchemaBuilder from 'schematized' // Typescript & ESM
const { default: SchemaBuilder } = require('schematized') // CommonJS

const builder = new SchemaBuilder()

// Consume JSON
builder.addObject({
  token: '74aea1a53d68b77e4f1f55fa90a7eb81',
  role: ['Basic'],
})

// Produce JSON Schemas!
const schema = builder.toPrettySchema()

Improve the schema with examples : See output

...

builder.addObject({
  token: 'Bearer 6498d9afc96d1d8d881a2b7ded4f9290',
  role: [
    'Admin',
    'Basic',
    'Publisher'
  ]
})

Improve the schema with existing schemas : See output

...

builder.addSchema({
  title: '/user server response',
  description: '/user server response'
})

Schema from the single example

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "token": {
      "type": "string",
      "maxLength": 32,
      "minLength": 32
    },
    "role": {
      "type": "array",
      "items": {
        "type": "string",
        "maxLength": 5,
        "minLength": 5
      }
    }
  },
  "required": [
    "role",
    "token"
  ],
  "additionalProperties": false,
  "maxProperties": 2,
  "minProperties": 2
}

Schema from the two examples

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "token": {
      "type": "string",
      "maxLength": 39,
      "minLength": 32
    },
    "role": {
      "type": "array",
      "items": {
        "type": "string",
        "maxLength": 9,
        "minLength": 5
      }
    }
  },
  "required": [
    "role",
    "token"
  ],
  "additionalProperties": false,
  "maxProperties": 2,
  "minProperties": 2
}

Schema from the two examples and the schema

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "/user server response",
  "description": "/user server response",
  "type": "object",
  "properties": {
    "token": {
      "type": "string",
      "maxLength": 39,
      "minLength": 32
    },
    "role": {
      "type": "array",
      "items": {
        "type": "string",
        "maxLength": 9,
        "minLength": 5
      }
    }
  },
  "required": [
    "role",
    "token"
  ],
  "additionalProperties": false,
  "maxProperties": 2,
  "minProperties": 2
}

📚 API

Method	Definition	Parameter
`.addObject($object)`	Add an example to improve the generated schema.	Valid JSON object
`.addSchema($schema)`	Add schemas to improve the generated schema.	Valid JSON Schema
`.toSchema()`	Generate the schema.	None
`.toPrettySchema()`	Generate the schema and pretty print.	None

🎯 Supported Schema Features

Visit the official JSON Schema site for specification details.

Types

Type	Supported
String	Yes
Number	Yes
Integer	Never
Object	Yes
Array	Yes
Tuple	Not yet
Boolean	Yes
Null	Yes

Typeless

Constraint	addSchema()	addObject()
title	Yes	Never
description	Yes	Never
$comment	Yes	Never
default	Not yet	Not yet
examples	Not yet	Not yet
enum	Not yet	Not yet
const	Not yet	Not yet
anyOf	Yes	Yes
allOf	Not yet	Not yet
oneOf	Not yet	Not yet
not	Not yet	Not yet
if/then/else	Not yet	Not yet

String

Constraint	addSchema()	addObject()
maxLength	Yes	Yes
minLength	Yes	Yes
format	Yes	Yes
pattern	Not yet	Not yet
contentMediaType	Not yet	Not yet
contentEncoding	Not yet	Not yet

Supported String formats

Format	Supported?
date-time	Yes
date	Yes
time	Yes
email	Yes
hostname	Not yet
idn-hostname	Not yet
ipv4	Yes
ipv6	Yes
uri	Yes
uri-reference	Not yet
url	Yes
uuid	Yes
iri	Not yet
iri-reference	Not yet
uri-template	Not yet
json-pointer	Not yet
relative-json-pointer	Not yet
regex	Not yet

Number

Constraint	addSchema()	addObject()
maximum	Yes	Yes
minimum	Yes	Yes
exclusiveMaximum	Not yet	Not yet
exclusiveMinimum	Not yet	Not yet
multiple	Not yet	Not yet

Object

Constraint	addSchema()	addObject()
propertyPatterns	Yes	Yes
additionalProperties	Yes	Yes
required	Yes	Yes
maxProperties	Yes	Yes
minProperties	Yes	Yes

Array

Constraint	addSchema()	addObject()
maxItems	Not yet	Not yet
minItems	Not yet	Not yet
uniqueItems	Not yet	Not yet

ryparker/schematized