Typoas is an OpenAPI 3.X generator for Typescript. It's inspired by openapi-generator but is written in Typescript for Typescript. The generator uses the Typescript AST to generate code instead on relaying on templates which allows better schemas definitions and other cool stuff.

Main features are:

• Fully typed and fully customizable
• References $ref handling (including cyclic refs)
• Tree Shaking out of the box
• Support for allOf, oneOf and anyOf schemas.
• Automatically convert format: 'date-time' to JS Date
• Handle API Key, HTTP Config and OAuth2¹ auth security schemes
• JSDoc for schemas and operations
• Uses fetch api (can be customized)
• Non JSON content type support
• Small bundle size
• And more...

¹: OAuth2 scheme does not handle flows to retrieve an accessToken. You need to provide your own accessToken through the provider.getConfig() function.

The project is split into 3 parts:

• @typoas/generator is used to generate the API specific code.
• @typoas/cli is a CLI entry point built on top of @typoas/generator.
• @typoas/runtime is the package that will be used by the generated code.

It will generate a single TS file containing all the code specific to the underlying API. This file only has a single dependency on @typoas/runtime. You need to manually add @typoas/runtime to your dependencies. It handles common things like serialization/authentification

You can generate the TS client from the spec from the command line:

yarn dlx @typoas/cli generate -i my-spec.json -o src/client.ts
npx @typoas/cli generate -i my-spec.json -o src/client.ts

Here is a short list of supported command line options:

    -i, --input [path/url]         Path or URL to the OpenAPI JSON specification (yaml/json format)
    -o, --output [path]            Path where to write the generated TS file
    -e,--generate-enums            Generate enums instead of literal string types where possible
    --js-doc, --no-js-doc          Whether to add JS Doc to the generated code (default: true)
    --wrap-lines-at                Define a maximum width for JS Doc comments, 0 to disable (default: 120)
    --only-types                   Use it to only generate types in #components/schemas/
    --no-fetcher-options           Use it to disable the additional param added to every operations
    --version                      Output the version number
    -h, --help                     Display help for command

    -n, --name                     Deprecated, name isn't used anymore

or you can use it in code:

import cli from '@typoas/cli';

await cli.run(
  [
    'generate',
    '-i',
    'https://raw.githubusercontent.com/github/rest-api-description/main/descriptions/api.github.com/api.github.com.yaml',
    '-o',
    `./src/github.ts`,
  ],
  {
    stdin: process.stdin,
    stdout: process.stdout,
    stderr: process.stderr,
  },
);

The API is still at an alpha stage, so it may break between minors.

It uses typescript API to generate usable code:

import { readFileSync, writeFileSync } from 'fs';
import { createPrinter, NewLineKind, SourceFile } from 'typescript';
import { generateClient, getStringFromSourceFile } from '@typoas/generator';

const specs = JSON.parse(readFileSync('path/to/github-openapi.json', 'utf8'));
const src = generateClient(specs, {
  /* options */
});
const data = getStringFromSourceFile(src);

writeFileSync('./src/client.ts', data, 'utf8');

Once the file is generated you'll be able to use it like this:

import { ServerConfiguration } from '@typoas/runtime';
import { createContext, pullsList } from './client';

const ctx = createContext();

pullsList(ctx, {
  repo: 'typoas',
  owner: 'embraser01',
})
  .then((list) => console.log('List of PRs', list))
  .catch((err) => console.error('Error while getting PRs', err));

The default fetch implementation is used (included in Node.js >= 18.0.0). You can always override the default fetch implementation in createContext

You can find examples in the examples folder.

Here is some notes on some known issues.

External references are not supported. Every $ref must be in the spec. An issue is open here.

Typoas has partial support for serialization specified here: https://swagger.io/docs/specification/serialization/

• It does support array serialization for query.
• It does NOT support serialization for path parameters with style label or matrix.
• It does NOT support serialization for query parameters with nested objects. It will be JSON.stringify
• It does NOT support serialization for headers or cookie parameters.

On query serialization, there can only be one style for a full operation. The first query param will set the style for the whole operation.

In v1, the whole API was generated in a single class. In V2 this was replaced by individual function which allow Tree Shaking. To get a similar result, you can use wrapApi helper:

import { ServerConfiguration, wrapApi } from '@typoas/runtime';
import { createContext, pullsList, issuesList } from './client';

const ctx = createContext();
const ghClient = wrapApi(ctx, {
  pullsList,
  issuesList,
  // ...
});

ghClient
  .pullsList(ctx, {
    repo: 'typoas',
    owner: 'embraser01',
  })
  .then((list) => console.log('List of PRs', list))
  .catch((err) => console.error('Error while getting PRs', err));

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

MIT