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📘️ openapi-typescript

🚀 Convert static OpenAPI schemas to TypeScript types quickly using pure Node.js. Fast, lightweight, (almost) dependency-free, and no Java/node-gyp/running OpenAPI servers necessary.

Features

  • Supports YAML and JSON formats
  • Supports advanced OpenAPI 3.1 features like discriminators
  • Supports loading via remote URL (simple authentication supported with the --auth flag)
  • Supports remote references: $ref: "external.yaml#components/schemas/User"
  • Fetches remote schemas quickly using undici

Examples

👀 See examples

Usage

Note:️ openapiTS requires VALID OpenAPI 3.x schemas to work, and this library does not handle validation. There are several quality tools that handle this like @apidevtools/swagger-parser. Make sure to validate your schemas first!

🖥️ CLI

🗄️ Reading a local schema

npx openapi-typescript schema.yaml --output schema.ts

# 🔭 Loading spec from schema.yaml…
# 🚀 schema.yaml -> schema.ts [250ms]
🦠 Globbing local schemas
npx openapi-typescript "specs/**/*.yaml" --output schemas/

# 🔭 Loading spec from specs/one.yaml…
# 🔭 Loading spec from specs/two.yaml…
# 🔭 Loading spec from specs/three.yaml…
# 🚀 specs/one.yaml -> schemas/specs/one.ts [250ms]
# 🚀 specs/two.yaml -> schemas/specs/two.ts [250ms]
# 🚀 specs/three.yaml -> schemas/specs/three.ts [250ms]

Thanks, @sharmarajdaksh!

☁️ Reading remote schemas

npx openapi-typescript https://petstore3.swagger.io/api/v3/openapi.yaml --output petstore.d.ts

# 🔭 Loading spec from https://petstore3.swagger.io/api/v3/openapi.yaml…
# 🚀 https://petstore3.swagger.io/api/v3/openapi.yaml -> petstore.d.ts [650ms]

Thanks, @psmyrdek!

🟦 Using in TypeScript

Import any top-level item from the generated spec to use it. It works best if you also alias types to save on typing:

import { components } from "./generated-schema.ts";

type APIResponse = components["schemas"]["APIResponse"];

Because OpenAPI schemas may have invalid TypeScript characters as names, the square brackets are a safe way to access every property.

🏗️ Operations

Operations can be imported directly by their operationId:

import { operations } from "./generated-schema.ts";

type getUsersById = operations["getUsersById"];

Thanks, @gr2m!

Fetching data

Simple example

Any fetch call can be typed from the paths like so:

import { paths } from './my-types';

const response: paths["/api/v1/user/{user_id}"]["get"][200 | 500] = await fetch(`/api/v1/user/${user_id}`).then((res) => res.json());

Or if you add the --path-params-as-types CLI flag, you can take advantage of more automatic inference:

import { paths } from './my-types';

const url = `/api/v1/user/${user_id}`;
const response: paths[url]["get"][200 | 500] = await fetch(url).then((res) => res.json());
openapi-typescript-fetch

You can generate a fully-typed Fetch API client from openapiTS types with the openapi-typescript-fetch package:

import { paths } from "./petstore";
import { Fetcher } from "openapi-typescript-fetch";

const fetcher = Fetcher.for<paths>();

// GET
const findPetsByStatus = fetcher.path("/pet/findByStatus").method("get").create();
const { status, data: pets } = await findPetsByStatus({
  status: ["available", "pending"],
});

// POST
const addPet = fetcher.path("/pet").method("post").create();
await addPet({ ... })

See docs

Thanks, @ajaishankar!

📖 Options

The following flags can be appended to the CLI command.

Option Alias Default Description
--help Display inline help message and exit
--version Display this library’s version and exit
--output [location] -o (stdout) Where should the output file be saved?
--auth [token] Provide an auth token to be passed along in the request (only if accessing a private schema)
--header -x Provide an array of or singular headers as an alternative to a JSON object. Each header must follow the key: value pattern
--headers-object="{…}" -h Provide a JSON object as string of HTTP headers for remote schema request. This will take priority over --header
--http-method -m GET Provide the HTTP Verb/Method for fetching a schema from a remote URL
--immutable-types false Generates immutable types (readonly properties and readonly array)
--additional-properties false Allow arbitrary properties for all schema objects without additionalProperties: false
--default-non-nullable false Treat schema objects with default values as non-nullable
--export-type -t false Export type instead of interface
--path-params-as-types false Allow dynamic string lookups on the paths object
--support-array-length false Generate tuples using array minItems / maxItems
--alphabetize false Sort types alphabetically

🚩 --path-params-as-types

By default, your URLs are preserved exactly as-written in your schema:

export interface paths {
  '/user/{user_id}': components["schemas"]["User"];
}

Which means your type lookups also have to match the exact URL:

import { paths } from './my-schema';

const url = `/user/${id}`;
type UserResponses = paths['/user/{user_id}']['responses'];

But when --path-params-as-types is enabled, you can take advantage of dynamic lookups like so:

import { paths } from './my-schema';

const url = `/user/${id}`;
type UserResponses = paths[url]['responses']; // automatically matches `paths['/user/{user_id}']`

Though this is a contrived example, you could use this feature to automatically infer typing based on the URL in a fetch client or in some other useful place in your application.

Thanks, @Powell-v2!

🚩 --support-array-length

This option is useful for generating tuples if an array type specifies minItems or maxItems.

For example, given the following schema:

components:
  schemas:
    TupleType
      type: array
      items:
        type: string
      minItems: 1
      maxItems: 2

Enabling --support-array-length would change the typing like so:

  export interface components {
    schemas: {
-     TupleType: string[];
+     TupleType: [string] | [string, string];
    };
  }

This results in more explicit typechecking of array lengths.

Note: this has a reasonable limit, so for example maxItems: 100 would simply flatten back down to string[];

Thanks, @kgtkr!

🐢 Node

npm i --save-dev openapi-typescript
import fs from "node:fs";
import openapiTS from "openapi-typescript";

// example 1: load [object] as schema (JSON only)
const schema = await fs.promises.readFile("spec.json", "utf8") // must be OpenAPI JSON
const output = await openapiTS(JSON.parse(schema));

// example 2: load [string] as local file (YAML or JSON; released in v4.0)
const localPath = new URL("./spec.yaml", import.meta.url); // may be YAML or JSON format
const output = await openapiTS(localPath);

// example 3: load [string] as remote URL (YAML or JSON; released in v4.0)
const output = await openapiTS("https://myurl.com/v1/openapi.yaml");

The Node API may be useful if dealing with dynamically-created schemas, or you’re using within context of a larger application. Pass in either a JSON-friendly object to load a schema from memory, or a string to load a schema from a local file or remote URL (it will load the file quickly using built-in Node methods). Note that a YAML string isn’t supported in the Node.js API; either use the CLI or convert to JSON using js-yaml first.

📖 Node options

The Node API supports all the CLI flags above in camelCase format, plus the following additional options:

Name Type Default Description
commentHeader string Override the default “This file was auto-generated …” file heading
inject string Inject arbitrary TypeScript types into the start of the file
transform Function Override the default Schema Object ➝ TypeScript transformer in certain scenarios
postTransform Function Same as transform but runs after the TypeScript transformation

🤖 transform / postTransform

If using the Node.js API, you can override the normal Schema Object transformer with your own. This is useful for providing enhanced functionality for specific parts of your schema.

For example, say your schema has the following property:

properties:
  updated_at:
    type: string
    format: date-time

By default, openapiTS will generate updated_at?: string; because it’s not sure which format you want by "date-time" (formats are nonstandard and can be whatever you’d like). But we can enhance this by providing our own custom formatter, like so:

const types = openapiTS(mySchema, {
  transform(schemaObject, metadata): string {
    if ("format" in schemaObject && schemaObject.format === "date-time") {
      return "Date";
    }
  },
});

That would result in the following change:

-  updated_at?: string;
+  updated_at?: Date;

Any Schema Object present in your schema will be run through this formatter (even remote ones!). Also be sure to check the metadata parameter for additional context that may be helpful.

There are many other uses for this besides checking format. Because this must return a string you can produce any arbitrary TypeScript code you’d like (even your own custom types).

Don’t forget about postTransform() as well! It works the same way, but runs after the TypeScript transformation so you can extend/modify types as-needed.

🏅 Project Goals

  1. Support converting any valid OpenAPI schema to TypeScript types, no matter how complicated.
  2. This library does NOT validate your schema, there are other libraries for that.
  3. The generated TypeScript types must match your schema as closely as possible (e.g. no renaming to PascalCase)
  4. This library should never require Java, node-gyp, or some other complex environment to work. This should require Node.js and nothing else.
  5. This library will never require a running OpenAPI server to work.

🤝 Contributing

PRs are welcome! Please see our CONTRIBUTING.md guide.

Contributors

Thanks goes to these wonderful people (emoji key):

Drew Powers
Drew Powers

💻 📖 🚇 ⚠️
Przemek Smyrdek
Przemek Smyrdek

💻 📖 🤔 ⚠️
Dan Enman
Dan Enman

🐛 💻
Atle Frenvik Sveen
Atle Frenvik Sveen

💻 📖 🤔 ⚠️
Tim de Wolf
Tim de Wolf

💻 🤔
Tom Barton
Tom Barton

💻 📖 🤔 ⚠️
Sven Nicolai Viig
Sven Nicolai Viig

🐛 💻 ⚠️
Sorin Davidoi
Sorin Davidoi

🐛 💻 ⚠️
Nathan Schneirov
Nathan Schneirov

💻 📖 🤔 ⚠️
Lucien Bénié
Lucien Bénié

💻 📖 🤔 ⚠️
Boris K
Boris K

📖
Anton
Anton

🐛 💻 🤔 ⚠️
Tim Shelburne
Tim Shelburne

💻 ⚠️
Michał Miszczyszyn
Michał Miszczyszyn

💻
Sam K Hall
Sam K Hall

💻 ⚠️
Matt Jeanes
Matt Jeanes

💻
Kristofer Giltvedt Selbekk
Kristofer Giltvedt Selbekk

💻
Elliana May
Elliana May

💻 ⚠️
Henrik Hall
Henrik Hall

💻 📖 ⚠️
Gregor Martynus
Gregor Martynus

💻 ⚠️ 🐛
Sam Mesterton-Gibbons
Sam Mesterton-Gibbons

💻 🐛 ⚠️
Rendall
Rendall

💻 🐛 ⚠️
Robert Massaioli
Robert Massaioli

💻 🐛
Jan Kuča
Jan Kuča

💻 ⚠️
Thomas Valadez
Thomas Valadez

📖
Asitha de Silva
Asitha de Silva

💻 🐛
Mikhail Yermolayev
Mikhail Yermolayev

🐛
Alex Batalov
Alex Batalov

💻 ⚠️
Federico Bevione
Federico Bevione

🐛 💻 ⚠️
Daisuke Yamamoto
Daisuke Yamamoto

💻 🐛 ⚠️
dnalborczyk
dnalborczyk

📖 💻 ⚠️
FabioWanner
FabioWanner

🐛 💻 ⚠️
Ash Smith
Ash Smith

💻 🐛 ⚠️
Micah Halter
Micah Halter

💻 ⚠️ 🐛
Yuto Yoshihara
Yuto Yoshihara

💻 🐛 ⚠️
Dakshraj Sharma
Dakshraj Sharma

💻
Shaosu Liu
Shaosu Liu

💻
Vytenis
Vytenis

💻
Eric Zorn
Eric Zorn

💻 ⚠️ 📖
Max Belsky
Max Belsky

💻 🐛
Peter Bech
Peter Bech

💻 🐛
Rusty Conover
Rusty Conover

💻
Dave Carlson
Dave Carlson

💻
ottomated
ottomated

💻 🐛
Artem Shuvaev
Artem Shuvaev

💻 🐛
ajaishankar
ajaishankar

📖
Dominik Dosoudil
Dominik Dosoudil

💻 ⚠️
tkr
tkr

💻 📖
berzi
berzi

💻 📖 ⚠️
Philip Trauner
Philip Trauner

💻 📖 ⚠️
Pavel Yermolin
Pavel Yermolin

💻 📖 ⚠️
Duncan Beevers
Duncan Beevers

💻 🐛 ⚠️
Timofey Kukushkin
Timofey Kukushkin

💻 ⚠️ 🐛
Dmitry Semigradsky
Dmitry Semigradsky

🐛 ⚠️ 💻
Jeremy Liberman
Jeremy Liberman

💻 ⚠️
Axel Hernández Ferrera
Axel Hernández Ferrera

💻 🐛 ⚠️
Loïc Fürhoff
Loïc Fürhoff

💻 ⚠️ 🐛
Bartosz Szczeciński
Bartosz Szczeciński

💻 🐛 ⚠️
Marco Salomone
Marco Salomone

💻 ⚠️
Yacine Hmito
Yacine Hmito

💻 ⚠️ 🐛
Sajad Torkamani
Sajad Torkamani

📖

This project follows the all-contributors specification. Contributions of any kind welcome!