@rtf/oazapfts
v3.6.0-alpha.1
Published
OpenApi TypeScript client generator
Downloads
1
Readme
🍻 oazapfts!
Generate TypeScript clients to tap into OpenAPI servers.
Features
- AST-based:
Unlike other code generators
oazapfts
does not use templates to generate code but uses TypeScript's built-in API to generate and pretty-print an abstract syntax tree. - Fast: The cli does not use any of the common Java-based tooling, so the code generation is super fast.
- Tree-shakeable: Individually exported functions allow you to bundle only the ones you actually use.
- Human friendly signatures: The generated api methods don't leak an HTTP-specific implementation details. For example, all optional parameters are grouped together in one object, no matter whether they end up in the headers, path or query-string.
Installation
npm install oazapfts
NOTE: With version 3.0.0 oazapfts has become a runtime dependency and the generated code does no longer include all the fetch logic.
Usage
oazapfts <spec> [filename]
Options:
--exclude, -e tag to exclude
--include, -i tag to include
Where <spec>
is the URL or local path of an OpenAPI or Swagger spec (in either json or yml) and <filename>
is the location of the .ts
file to be generated. If the filename is omitted, the code is written to stdout.
Overriding the defaults
The generated file exports a defaults
constant that can be used to override the basePath
, provide a custom fetch
implementation or to send additional headers with each request:
import * as api from "./api.ts";
import nodeFetch from "node-fetch";
api.default.basePath = "https://example.com/api";
api.defaults.headers = {
access_token: "secret",
};
api.defaults.fetch = nodeFetch;
Consuming the generated API
For each operation defined in the spec the generated API will export a function with a name matching the operationId
. If no id is specified, a reasonable name is generated from the HTTP verb and the path.
The last argument of each function is an optional RequestOpts
object that can be used to pass options to the fetch
call, for example to pass additional headers or an AbortSignal
to cancel the request later on.
Each function returns a Promise for an ApiResponse
which is an object with a status
and a data
property, holding the HTTP status code and the properly typed data from the response body. Since an operation can return different types depending on the status code, the actual return type is a union of all possible responses, discriminated by their status.
Consider the following code generated from the petstore.json
example:
export function getPetById(petId: number, opts?: RequestOpts) {
return fetchJson<
| {
status: 200;
data: Pet;
}
| {
status: 400;
data: string;
}
| {
status: 404;
data: string;
}
>(`/pet/${petId}`, {
...opts,
});
}
In this case the data
property is typed as Pet|string
. We can use a type guard to narrow down the type to Pet
:
const res = await api.getPetById(1);
if (res.status === 200) {
const pet = res.data;
// pet is properly typed as Pet
}
if (res.status === 404) {
const message = res.data;
// message is a string
} else {
// handle the error
}
The above code can be simplified by using the handle
helper:
import { handle } from "oazapfts";
await handle(api.getPetById(1), {
200(pet) {
// pet is properly typed as Pet
},
404(message) {
// message is as string
},
});
The helper will throw an HttpError
error for any unhanled status code unless you add a default
handler:
await handle(api.getPetById(1), {
200(pet) {
// ...
},
default(status, data) {
// handle error
},
});
Optimistic APIs
Instead of handling errors right in place we can also use the ok
helper:
import { ok } from "oazapfts";
const pet = await ok(api.getPetById(1));
With this pattern pet
will be typed as Pet
and a HttpError
will be thrown in case of an error.
You can even turn your whole API into an optimistic one:
import { optimistic } from "oazapfts";
import * as rawApi from "./api.ts";
const api = optimistic(rawApi);
const pet = await api.getPetById(1);
CLI
Since version 3.1.0 you can also use the --optimistic
flag on the command line to generate an optimistic API by default.
About the name
The name comes from a combination of syllables oa (OpenAPI) and ts (TypeScript) and is pronounced 🗣 like the Bavarian O'zapt'is! (it's tapped), the famous words that mark the beginning of the Oktoberfest.
License
MIT