-
RPC-like client with no codegen
Fully typed RPC-like client, with no need for code generation! -
API design agnostic
REST? HTTP-RPC? Your own custom hybrid? rescript-rest doesn't care! -
First class DX
Less unnecessary builds in monorepos, instant compile-time errors, and instantly view endpoint implementations through your IDEs "go to definition" -
Small package size and tree-shakable routes
Routes comple to simple functions which allows tree-shaking only possible with ReScript.
⚠️ rescript-rest relies on rescript-schema which usesevalfor parsing. It's usually fine but might not work in some environments like Cloudflare Workers or third-party scripts used on pages with the script-src header.
Install peer dependencies rescript (instruction) and rescript-schema (instruction).
Then run:
npm install rescript-restAdd rescript-rest to bs-dependencies in your rescript.json:
{
...
"bs-dependencies": ["rescript-rest"],
}Easily define your API contract somewhere shared, for example, Contract.res:
let getPosts = Rest.route(() => {
path: "/posts",
method: Get,
variables: s => {
"skip": s.query("skip", S.int),
"take": s.query("take", S.int),
"page": s.header("x-pagination-page", S.option(S.int)),
},
responses: [
s => {
s.status(#200)
s.field("posts", S.array(postSchema))
},
],
})Consume the API on the client with a RPC-like interface:
let client = Rest.client(~baseUrl="http://localhost:3000")
let result = await client.call(
Contract.getPosts,
{
"skip": 0,
"take": 10,
"page": Some(1),
}
// ^-- Fully typed!
) // ℹ️ It'll do a GET request to http://localhost:3000/posts?skip=0&take=10 with the `{"x-pagination-page": "1"}` headersFulfil the contract on your sever, with a type-safe Fasitfy integration:
let app = Fastify.make()
app->Fastify.route(Contract.getPosts, variables => {
queryPosts(~skip=variables["skip"], ~take=variables["take"], ~page=variables["page"])
})
// ^-- Both variables and return value are fully typed!
let _ = app->Fastify.listen({port: 3000})Examples from public repositories:
You can define path parameters by adding them to the path strin with a curly brace {} including the parameter name. Then each parameter must be defined in variables with the s.param method.
let getPost = Rest.route(() => {
path: "/api/author/{authorId}/posts/{id}",
method: Get,
variables: s => {
"authorId": s.param("authorId", S.string->S.uuid),
"id": s.param("id", S.int),
},
responses: [
s => s.data(postSchema),
],
})
let result = await client.call(
getPost,
{
"authorId": "d7fa3ac6-5bfa-4322-bb2b-317ca629f61c",
"id": 1
}
) // ℹ️ It'll do a GET request to http://localhost:3000/api/author/d7fa3ac6-5bfa-4322-bb2b-317ca629f61c/posts/1If you would like to run validations or transformations on the path parameters, you can use rescript-schema features for this. Note that the parameter names in the s.param must match the parameter names in the path string.
You can add query parameters to the request by using the s.query method in the variables definition.
let getPosts = Rest.route(() => {
path: "/posts",
method: Get,
variables: s => {
"skip": s.query("skip", S.int),
"take": s.query("take", S.int),
},
responses: [
s => s.data(S.array(postSchema)),
],
})
let result = await client.call(
getPosts,
{
"skip": 0,
"take": 10,
}
) // ℹ️ It'll do a GET request to http://localhost:3000/posts?skip=0&take=10You can also configure rescript-rest to encode/decode query parameters as JSON by using the jsonQuery option. This allows you to skip having to do type coercions, and allow you to use complex and typed JSON objects.
You can add headers to the request by using the s.header method in the variables definition.
let getPosts = Rest.route(() => {
path: "/posts",
method: Get,
variables: s => {
"authorization": s.header("authorization", S.string),
"pagination": s.header("pagination", S.option(S.int)),
},
responses: [
s => s.data(S.array(postSchema)),
],
})For some low-level APIs, you may need to send raw body without any additional processing. You can use s.rawBody method to define a raw body schema. The schema should be string-based, but you can apply transformations to it using s.variant or s.transform methods.
let getLogs = Rest.route(() => {
path: "/logs",
method: POST,
variables: s => s.rawBody(S.string->S.transform(s => {
// If you use the route on server side, you should also provide the parse function here,
// But for client side, you can omit it
serialize: logLevel => {
`{
"size": 20,
"query": {
"bool": {
"must": [{"terms": {"log.level": ${logLevels}}}]
}
}
}`
}
})),
responses: [
s => s.data(S.array(S.string)),
],
})
let result = await client.call(
getLogs,
"debug"
) // ℹ️ It'll do a POST request to http://localhost:3000/logs with the body `{"size": 20, "query": {"bool": {"must": [{"terms": {"log.level": ["debug"]}}]}}}` and the headers `{"content-type": "application/json"}`You can also use routes with rawBody on the server side with Fastify as any other route:
app->Fastify.route(getLogs, async variables => {
// Do something with variables and return response
})🧠 Currently Raw Body is sent with the application/json Content Type. If you need support for other Content Types, please open an issue or PR.
Responses are described as an array of response definitions. It's possible to assign the definition to a specific status using s.status method.
let createPost = Rest.route(() => {
path: "/posts",
method: Post,
variables: _ => (),
responses: [
s => {
s.status(#201)
Ok(s.data(postSchema))
},
s => {
s.status(#404)
Error(s.field("message", S.string))
},
],
})You can use s.status multiple times. To define a range of response statuses, you may use 1XX, 2XX, 3XX, 4XX and 5XX. If s.status is not used in a response definition, it'll be treated as a default case, accepting a response with any status code.
let createPost = Rest.route(() => {
path: "/posts",
method: Post,
variables: _ => (),
responses: [
s => {
s.status(#201)
Ok(s.data(postSchema))
},
s => {
s.status(#404)
Error(s.field("message", S.string))
},
s => {
s.status(#"5XX")
Error("Server Error")
},
s => Error("Unexpected Error"),
],
})Responses from an API can include custom headers to provide additional information on the result of an API call. For example, a rate-limited API may provide the rate limit status via response headers as follows:
HTTP 1/1 200 OK
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 99
X-RateLimit-Reset: 2016-10-12T11:00:00Z
{ ... }
You can define custom headers in a response as follows:
let ping = Rest.route(() => {
path: "/ping",
method: Get,
summary: "Checks if the server is alive",
variables: _ => (),
responses: [
s => {
s.status(#200)
s.description("OK")
{
"limit": s.header("X-RateLimit-Limit", S.int->S.description("Request limit per hour.")),
"remaining": s.header("X-RateLimit-Remaining", S.int->S.description("The number of requests left for the time window.")),
"reset": s.header("X-RateLimit-Reset", S.string->S.datetime->S.description("The UTC date/time at which the current rate limit window resets.")),
}
}
],
})Fastify is a fast and low overhead web framework, for Node.js. You can use it to implement your API server with rescript-rest.
To start, install rescript-rest and fastify:
npm install rescript-rest fastifyThen define your API contract:
let getPosts = Rest.route(() => {...})And implement it on the server side:
let app = Fastify.make()
app->Fastify.route(Contract.getPosts, async variables => {
// Implementation where return type is promise<'response>
})
let _ = app->Fastify.listen({port: 3000})🧠
rescript-restships with minimal bindings for Fastify to improve the integration experience. If you need more advanced configuration, please open an issue or PR.
- Currently supports routes only with a single response definition
- Doesn't support array/object-like query params
- Has issues with paths with
:
- Support query params
- Support headers
- Support path params
- Implement type-safe response
- Support custom fetch options
- Support non-json body
- Generate OpenAPI from Contract
- Generate Contract from OpenAPI
- Server implementation with Fastify
- NextJs integration
- Add TS/JS support