denosaurs / typefetch

📤 Magically generate `fetch` types from OpenAPI schemas for zero-cost browser-native api clients

TypeFetch

TypeFetch is a tool for generating zero-cost type-safe fetch clients from OpenAPI schemas. It works everywhere you can call fetch, and anywhere you can use TypeScript.

Usage

To use TypeFetch, you need to have an OpenAPI schema. You can either provide a local file path or a URL to the schema (which can be either json or yaml), then all you need to do is run the cli using deno, node, or any other JavaScript runtime supported by the jsr registry.

deno run -A jsr:@denosaurs/typefetch

Usage: typefetch [OPTIONS] <PATH>
Options:
  -h, --help                  Print this help message
  -V, --version               Print the version of TypeFetch
  -o, --output   <PATH>       Output file path                                            (default: typefetch.d.ts)
      --config   <PATH>       File path to the tsconfig.json file
      --import   <PATH>       Import path for TypeFetch                                   (default: https://raw.githubusercontent.com/denosaurs/typefetch/main)
      --base-url <URL>        A custom base url for paths to start with
      --include-base-url      Include the base url in the generated paths                 (default: false)
      --include-server-urls   Include server URLs from the schema in the generated paths  (default: true)
      --include-relative-url  Include relative URLs in the generated paths                (default: false)

Example

deno run -A jsr:@denosaurs/typefetch https://api.jsr.io/.well-known/openapi

This will generate a typefetch.d.ts file in the current directory, which will modify the global scope and the type definitions for the fetch function and all types defined within the schema. For example:

declare global {
  ...
  /**
   * Returns a list of packages
   * @summary List packages
   */
  function fetch(
    input: `https://api.jsr.io/packages` | `/packages`,
    init?: Omit<RequestInit, "method" | "body" | "headers"> & {
      method: "GET";
    },
  ): Promise<
    & Omit<
      Response,
      "ok" | "status" | "arrayBuffer" | "blob" | "formData" | "json" | "text"
    >
    & (
      | ({
        ok: true;
        status: 200;
        json(): Promise<{ items: Package[]; total: number }>;
        text(): Promise<JSONString<{ items: Package[]; total: number }>>;
      })
      | ({
        ok: false;
        status: 400;
        json(): Promise<Error>;
        text(): Promise<JSONString<Error>>;
      })
    )
  >;
  ...
}

Which now allows you to use the fetch function with the https://api.jsr.io/packages endpoint as following:

const response = await fetch("https://api.jsr.io/packages");

// The ok and status properties work as discriminators here to narrow the
// types of the response. That way the json and text methods are made
// type-safe.
if (response.ok) {
  console.assert(response.status === 200);

  const { items, total } = await response.json();
  // even this works because we augment the global JSON object!
  const { items, total } = JSON.parse(await response.text());
} else {
  console.assert(response.status === 400);

  const error = await response.json();
  // or
  const error = JSON.parse(await response.text());
}

Maintainers

• Elias Sjögreen (@eliassjogreen)

Contributing

Pull request, issues and feedback are very welcome. Code style is formatted with deno fmt and commit messages are done following Conventional Commits spec.

Please use it! And let us know if you have any issues, feedback or requests.

Licence

Copyright 2024, the Denosaurs team. All rights reserved. MIT license.