JSON Schema to GraphQL

This is a tool that compiles JSON Schema to GraphQL schema output types. It uses awesome json-schema-to-typescript under the hood and it's basically custom generator for it, that instead of TypeScript outputs GraphQL using same AST.

Example

Input:

{
  "title": "Example Schema",
  "type": "object",
  "properties": {
    "firstName": {
      "type": "string"
    },
    "lastName": {
      "type": "string"
    },
    "age": {
      "description": "Age in years",
      "type": "integer",
      "minimum": 0
    },
    "hairColor": {
      "title": "Hair color",
      "enum": ["black", "brown", "blue"],
      "type": "string"
    }
  },
  "additionalProperties": false,
  "required": ["firstName", "lastName"]
}

Output:

type ExampleSchema {
  firstName: String!
  lastName: String!

  """
  Age in years
  """
  age: Int
  hairColor: HairColor
}

enum HairColor {
  black
  brown
  blue
}

Installation

Using Yarn:

yarn add @splitti/json-schema-to-graphql

Or, using NPM:

npm install @splitti/json-schema-to-graphql --save

CLI Usage

json-schema-to-graphql example.json example.graphql

Where example.json is your JSON schema file and example.graphql is the output schema is being exported.

Known limitations and missing features

• There is no unions of scalar values in GraphQL
  • Those would be needed to be wrapped to objects
• There is no string or number literals in the GraphQL
  • Unions of string literals are transformed to enums
• GraphQL doesn't support intersections meaning allOf definitions need to be merged
  • Currently has on quite limited support for objects
  • Available merge tools don't seem to maintain object reference equality causing duplicate types.
• There is no support for tuples in GraphQL
  • Currently those are changed to lists when possible
• There is no support for generating input types for now

Development

This library uses dts-cli as zero configuration development tool.

Start development watcher with:

npm run start

Run tests with:

npm run test