cake-rpc is a lightweight library for defining, implementing and consuming restful APIs using a fully structured interface with both static & runtime type safety. With cake-rpc you can easily:

• Define restful services using an easy js\ts lib 🎬
• Implement them in your express server (plugs right in as a router, no config needed!) 🚂
• Use from your client as if it was a class you imported 🌍
• Keeps you type safe: full typescript support, as well as runtime type validation 🎖

Getting Started in 3 Steps

Step 1: Define your service

Start by installing cake-rpc in your project:

npm install @cakery/cake-rpc

Now create a new file called service.ts, and define a service using createService:

import { createService } from '@cakery/cake-rpc';

export const echoService = createService({
  echo: {
    path: '/echo',
    method: 'POST',
    request: (z) => ({
      reqText: z.string().max(20),
    }),
    response: (z) => ({
      resText: z.string().max(20),
    }),
  },
});

We declared a service (called echoService), with one method called: echo:

• The path (url) to the method is /echo
• The http method to be used is POST
• The request body should contain a single string called reqText with up to 20 chars (more about schemas in the relevant chapter)
• The response body will contain a single string called reqText with up to 20 chars

Step 2: Implement using your Express server

cake-rpc is designed to be plugged into your express server with zero boilerplate or configuration. You don't need to change anything, just implement an express router!

Go to your express app and add the following:

import { createRouter } from '@cakery/cake-rpc/express';
import { echoService } from './service';

export const echoServiceRouter = createRouter(echoService, {
  echo: (req, res) => {
    res.send({ resText: req.body.reqText });
  },
});

app.use('/api', echoServiceRouter);

What we did is to create an express router from our service, where we implemented the echo method:

• The echo implementation is a simple express route
• No need to validate input! The request body is automatically checked for your before your route is even run
• If you are using typescript: req.body is fully typed for your convenience!
• If you are using typescript: res.json and res.send are fully typed for your convenience!
• The entire router is nested under /api. In theory, you can plug in as many cake-rpc service you'd like, and simply nest them under different routes!

We then took the router and utilized it by our express app!

Step 3: Use your service from the client

Now we want to actually use our echo service. Let's go to our client's code and add the following:

import { createClient } from '@cakery/cake-rpc/client';
import { echoService } from '../service/echo';

const echoClient = createClient(echoService, '/api');

echoClient.echo({ reqText: 'hello, world!' })
  .then(res => console.log(res.data.resText));

Here, we simply created an instance of our echo service's client, and used it to echo hello, world:

• We created the client with echoService as the service, and /api as base url. If your client is served from the same server you used in step 2, you can keep it that way. Otherwise, you need to input full url (e.g. http://localhost:1234/api). If you are serving your app from a different server, don't forget cors policy as well!
• The created client has all the methods from echoService. We can invoke any of them with the relevant body!
• The method resolves to an axios response, where we have status for http status code, and data for the body
• If you are using typescript: .echo({...}) is fully typed for your convenience!
• If you are using typescript: res.data is fully typed for your convenience!

Congratulations! You have successfully implemented your first cake-rpc service. You can go ahead and give it a spin in your existing express applications - no boilerplate, configurations or strings attached!

Usage

Installing cake-rpc

You can start by installing cake-rpc using your favorite package manager:

npm:

npm install cake-rpc

Or yarn:

yarn add cake-rpc

The cake-rpc actually has three entrypoints:

1. The first one is the default @cakery/cake-rpc import, which provides you with the service factory
2. The second one is @cakery/cake-rpc/express - this is where you import the server-side tools into your express application
3. The third one is @cakery/cake-rpc/client - this is where you import the client factory from, and should be used by your client application

Creating Service Schemas

At its core, cake-rpc operates with services. You can think of them as interfaces that define all the api methods that you want to expose.

In order to create a new service, you need to import the createService factory method from the main entrypoint:

import { createService } from '@cakery/cake-rpc';

You can then use it to create a service schema:

const guestListService = createService({
  listGuests: { ... },
  addGuest: { ... },
  removeGuest: { ... }
})

In this example, we created a service with three methods: listGuests, addGuest and removeGuest.

Every method has four parameters to describe:

1. The path (url) to it
2. The http method to use
3. The type of the request body (or query string, for GET \ DELETE requests)
4. The type of the response body

Take a look at the following example for addGuest:

const guestListService = createService({
  ...
  addGuest: {
    path: '/guests',
    method: 'POST',
    request: (z) => ({
      name: z.string().min(3).max(20),
      age: z.number().int().positive(),
      plusOne: z.boolean(),
    }),
    response: (z) => ({
      success: z.boolean(),
    }),
  },
  ...
})

The request is a POST to /guests, and should denote name, age, and plusOne fields. The response denotes success using a boolean value.

The schema builder for the request and the response actually uses zod, a light and powerful schema declaration library.

Once we're done defining our service, it's time to implement it!

Implementing Service in Express

cake-rpc wants to take as little of your attention as possible, unlike other terrific fullstack frameworks, such as next.js or meteor. As a matter of fact, we consider cake-rpc a library, and not a framework.

As such, cake-rpc plugs into your express application as a router.

You can start by importing the router factory:

import { createRouter } from '@cakery/cake-rpc/express';

Now, create an express router for your service:

const guestListRouter = createRouter(guestListService, {
  listGuests: (req, res) => { ... },
  addGuest: (req, res) => { ... },
  removeGuest: (req, res) => { ... },
})

For every method, you simply have to define an express handler that would handle it - as simple as that. All the requests made to your server are validated before they are passed to the handler, so you can rest assured that if a request made it to your code, it was already validated!

Few other neat quality of life features when implementing your router are:

1. The router supports async functions, including error handling
2. The request is fully typed - req.body will match the schema that you defined for the request
3. The response is fully typed - req.json and req.data will hint at the schema that you defined for the response

Finally, attach the router to your express app:

app.use(guestListRouter);

As we said, the router is a simple express router, so you can use it as any other middleware, for example:

app.use('/api/v1', [cors(), authenticateUser(), guestListRouter]);

Initializing your Client

Now that you've implemented your server, you can initialize your client.

Start by importing the createClient factory:

import { createClient } from '@cakery/cake-rpc/client';

The next thing to do is to create your client:

const guestListClient = createClient(guestListService, '/');

The createClient factory returns a full client that is based on the famous axios library. Think of it as a typed axios client: you can configure it as you would axios, and the response format is similar to axios, but instead of get post put (and other) methods, you get the service's methods (in our case, listGuests, addGuest and deleteGuest).

The createClient function receives up to three parameters:

1. The service definition (required) - the object we created using createService
2. The base url (required) - the base url under which the router can be found (can be relative if your app is served from the same server where the api can be found, otherwise it should be a full url)
3. Axios configuration (optional) - a configuration object that will be passed to the underlying axios client.

When invoking a method, all you need to do is pass the request payload:

guestListClient.addGuest({ name: 'Roy', age: 28, plusOne: true });

If you are using typescript, addGuest will be fully typed and hint at the correct request structure. In addition, all requests are validated on the client before being sent to the server for your convenience.

Additionally, you can pass an Axios config to the request as well, e.g.:

guestListClient.addGuest({ name: 'Roy', age: 28, plusOne: true }, { headers: { 'x-my-identity': 'super admin' } });

ℹ️ Regarding your bundle: if you are bundling your apps using webpack or parcel, fear not! cake-rpc only brings the essential code for your client-side application, since you import it from @cakery/cake-rpc/client. Nothing related to express will be imported.

Making API Changes (Backwards Compatibility)

APIs are dynamic beings - we change and we add to them all the time. Question being asked - how does cake-rpc handle API changes? Let's divide it into two parts: requests and responses.

Requests

If you are adding fields to your request schemas, you cant take one of two approaches:

1. Make it optional. That way, you can provide backwards compatibility for older clients:

addGuest: {
  request: (z) => ({
    name: z.string().min(3).max(20),
    age: z.number().int().positive(),
    plusOne: z.boolean(),
+   hasARide: z.boolean().optional()
  }),
}

2. Make the new field required. In that case, all clients using the older schema will be rejected by your new server.

One way or another, if you are making breaking changes to your api, we suggest that you follow api versioning best practices.

Responses

By default, you can always add new fields to the response. The cake-rpc client takes that into account, and simply ignores fields it is not familiar with.

That said, if you want to remove fields from the response, it will most definitely break the client, causing it to throw accordingly and tell you to check your compatibility with the server schema. Therefore, if you want to remove fields, consider this a breaking api change, and preferably follow through with api versioning.

Working in Multi-Package Workspaces

Of course, many projects tend to put the server and the client in separate packages. Are you using lerna or yarn workspaces? We got you covered!

You can basically create your services as packages within your workspace \ monorepo, and consume them both in your server and client projects:

The Easy Way

Cake comes with a straight-forward tool called create-cake-package. When run, it will generate a package with all the required setup, so you can go ahead and start implementing your service immediately. Use it by running the following command:

npx create-cake-package

The Custom Way

Alternatively, you can create such packages on your on, in a way that matches your workflow. The only dependency for said packages would be cake-rpc itself.

You can take a look at a minimal implementation here.

FAQ

Why cake-rpc?

I've been working on fullstack web projects for a long time now, and no matter where I worked and on which system, there was always a single most important concern: how do we manage integrations between multiple services, servers and clients and not lose our minds?

In one of my workplaces, I attempted to solve this exact problem, and came up with a system that I am proud to say is used by the entire company (and even our dev sdk) to this day. From it, I learned the following:

1. Most people want to write as little boilerplate as possible
2. But they almost never want to commit their entire codebase to a full framework

That is, people want things to work fast and simple, and not have to wrap their entire program around a specific framework that wraps around and abstracts away their simple express \ react apps.

That's why I came up with cake-rpc - inspired by my experience with said libraries, I wanted to create a library that is as simple to plug into as an express router, and which you don't have to commit to - if you don't feel like using it anymore, just uninstall it and you're done. In short: comprehensive, but non-intrusive.

What if I'm using Koa? Or Fastify? Or something else?

As you can see, the createRouter method from express is imported from @cakery/cake-rpc/express. In the future, and according to popular demand, adapters for koa, fastify and others might be added as well.

What if I don't want Axios?

I went with axios first as it is my own requests library of choice. I do intend to implement a client base on fetch as well, so if you don't want to include axios in your bundle and prefer to use fetch - you will be able to pretty soon!

What about other languages?

In order to keep it simple, cake-rpc is currently directed at a full js\ts stack. In the future, if demand arises, it is not out of the question to port cake to other languages as well!

Contribution

I've yet to set up a contribution guide per se, but feel free to open issues and pull requests! I promise to try and be attentive to your requests and contributions.

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