Code generation from OpenAPI 3 to TypeScript

Lightweight and simple. Can be used for browser's and for Node.js ecosystems. Now supports converting from OpenAPI 3 to TypeScript types (OpenAPI 2 and below are not supported).

For example, creates constructions such as (click to expand):

/**
 * Typical 401 response
 */
export interface HttpErrorUnauthorized {
  /**
   * Error message
   */
  message: string;

  /**
   * Data appropriate to
   * [WWW-Authenticate](https://tools.ietf.org/html/rfc7235#section-3.1).
   */
  wwwAuthenticate?: {
    /**
     * Prompt to authenticate
     */
    title: string;

    /**
     * Kind of authorization user has to use
     */
    type: string;

    /**
     * Type of authority ("barrier" or etc.)
     */
    realm: string;
  };
}

export interface GetParametersMeta_response401
  extends HttpErrorUnauthorized {

  /**
   * Error message
   */
  message: string;

  /**
   * Data appropriate to
   * [WWW-Authenticate](https://tools.ietf.org/html/rfc7235#section-3.1).
   */
  wwwAuthenticate?: {
    /**
     * Prompt to authenticate
     */
    title: string;

    /**
     * Kind of authorization user has to use
     */
    type: string;

    /**
     * Type of authority ("barrier" or etc.)
     */
    realm: string;
  };
}

/**
 * Kind of request error: syntax or semantic. Syntax error means the
 * application logic error, semantics — error of data, that contragent
 * inputs.
 */
export enum HttpErrorBadRequestTypeEnum {
  Syntax = "syntax",
  Semantic = "semantic"
}

/**
 * Typical response one Bad Request Error (400)
 */
export interface HttpErrorBadRequest {
  /**
   * Common error message
   */
  message: string;

  /**
   * Kind of request error: syntax or semantic. Syntax error means the
   * application logic error, semantics — error of data, that contragent
   * inputs.
   */
  type?: HttpErrorBadRequestTypeEnum;

  /**
   * Explained description of error
   */
  description?: string;

  /**
   * Additional list of errors with JSON-pointers
   */
  errors?: Array<{
    originalMessage: string;

    message?: string;

    jsonPointer: string;
  }>;
}

/**
 * ## MetaDataView
 * MetaData helps decide what the method has to use to
 * interpret and render parameter or category of parameters.
 */
export type GetParametersMeta_response200 = Array<Category | Parameter>;

---

🚦 Status of project

• Stabilization: ready to use in non-production projects (see Road Map).
• Not supported YML (only JSON). Will be supported soon. Now, you can use something like js-yaml
• 🐞 UPDATE: Fixed problem with infinity loop in recursive types!

Please, if it possible: send me your schemas that not converts properly.

Online demo

Work in progress! Now, see how to use.

Road map

Work is just started, and current functionality (creating TypeScript types) — It's just a first part of the supposed functionality. With time, it's supposed, possibilities of this plugin will be extended by:

• Make project well documented [in progress]
• YAML support [in progress]
• Stabilization [in progress]
• Playground site [in progress]
• Plugins support
• Generation classes (now creates only interfaces) with internal validation [ concept description is coming soon ]
• Generation API Classes
  • Solutions for AngularX based on Assured requests idea with internal validation [ concept description is coming soon ]
  • May be, something else...
• DDD-tools (Start kit for OpenAPI3-projects):
  • Bundler for complex files structure. Need fo organization complex API-libraries.
  • Dredd
  • Most populars doc-generators (at least, Redoc and SwaggerUI)
  • Convention for working with DDD OpenAPI3
• Other languages (is there are need for it?): Kotlin, Java, PHP,

Ideology

• Data format loyalty: it's should be as useful as it possible regardless validity of source data.
• Integration: solution should be able to be integrated to any system (at least, based on NPM). It's mean, should have CLI and API.

Why not swagger-codegen?

• Uses NPM instead Java (install via npm and easy-integratable)
• Lightweight (swagger-codegen solution — it's about a 14mb for ready JAR)
• Supports OpenAPI3
• Above all, intended for TypeScript

Install

1. Install TypeScript

npm install typescript@latest -g

2. Install oapi3codegen global (for CLI using)

npm install oapi3codegen -g

3. Install oapi3codegen for local project

npm install oapi3codegen --save

Using via CLI

oapi3codegen --srcPath /PATH/TO/SRC/open-api-file.json --destPath /PATH/TO/DEST --separatedFiles true

CLI arguments

CLI Argument	Description
srcPath	Path of url of JSON file with OpenAPI3 specification
destPath	Path for destination directory
separatedFiles	Whether should converted types be saved in separated files, or in single file

Also, you can set some of options for convertor's configuration config via CLI:

Option	Description
defaultContentType	Default content-type contains no prefixes/suffixes in type names.
implicitTypesRefReplacement	Mode when models that refer to any models via $ref are replacing implicitly even if firsts have names

Using via API (TypeScript)

You can convert whole OpenAPI3-specification:

import { Convertor } from 'oapi3codegen';

const convertor: Convertor = new Convertor();

/**
 * Base models of specification:
 *  - Requests bodies models
 *  - Requests params sets models
 *  - Responses models
 *
 * Converting starts from entry points and extracts
 * referred types and dependencies. It s why we need
 * to get "entry points". 
 */
const entryPoints = convertor.getOAPI3EntryPoints(context);

/**
 * Rendering each type: every entry point and each of
 * theirs related types.
 */
Convertor.renderRecursive(
    entryPoints,
    (descriptor: DataTypeDescriptor, text) => {
        // Here your code: you get text and type descriptor.
        // You can see how oapi3codegen's CLI uses this calback here:
        // https://github.com/koshevy/oapi3codegen/blob/master/cli.ts#L73
    }
);

And also, you can convert stand-alone JSON-schema into type descriptor, that could be rendered:

import { Convertor } from 'oapi3codegen';
// you need prettier to beautify result of rendering
import * as prettier from 'prettier';
// provides `_.each(...)` for our example
import * as _ from 'lodash';

const convertor: Convertor = new Convertor();

const anotherJsonSchemaObject = {
    "title": "Person",
    "description": "Information about person you have to register in your system.",
    "type": "object",
    "properties": {
        "firstName": {
            "type": "string"
        },
        "lastName": {
            "type": "string"
        },
        "age": {
            "description": "Age in years",
            "type": "integer",
            "minimum": 0
        }
    },
    "required": ["firstName", "lastName"]
};

const convertResult = convertor.convert(
    anotherJsonSchemaObject,
    {},
    'AnotherType'
);

_.each(convertResult, typeDescriptor => {
    const typeCode = prettier.format(
        typeDescriptor.render([]),
        {parser: 'typescript'}
    );

    console.log(typeCode);
});

And this code will print result:

/**
 * ## Person
 * Information about person you have to register in your system.
 */
export interface AnotherType {
  firstName: string;

  lastName: string;

  /**
   * Age in years
   */
  age?: number;
}

API (TypeScript)

Coming soon...

How to extend?

Coming soon...