tyrann-io

Welcome to tyrann-io 👋

Yet another easy solution to keep your REST calls and data types in the same place (deprecating tyrann)

🏠 Homepage

Prerequisites

• ES6
• TypeScript >= 4.1

Install

yarn add axios tyrann-io

Usage

1. Describe your data

import { tyrann } from 'tyrann-io';
import * as t from 'io-ts';

const apis = tyrann({
  '/user/{id}': {
    get: {
      path: t.type({
        id: t.number,
      }),
      response: {
        200: t.type({
          name: t.string,
          address: t.string,
        }),
      },
    }
  },
  '/login': {
    post: {
      body: t.type({
        username: t.string,
        password: t.string,
      }),
      response: {
        200: t.type({
          successful: t.boolean,
        }),
        403: t.type({
          successful: t.boolean,
          reason: t.string,
        })
      },
    }
  },
};

2. Ask for what you want

const response = await apis.get(
  "/user/{id}",
  {
    path: {
      id: 1,
    }
  }
);

3. Get predictable results

console.log(response[200]);
{
  "name": "John Doe",
  "address": "Nowhere"
}

User Guide

tyrann-io works in tandem with io-ts. This means tyrann typically harnesses the power of io-ts to define interface and check runtime types to ensure a predictable behavior of REST calls.

API Definition

To define a set of REST calls, you first need to import tyrann-io.

import { tyrann } from 'tyrann-io';
import * as t from 'io-ts';

const apis = tyrann({});

To define an API, add an entry to the input, with the key as the (template) of path:

const apis = tyrann({
  '/user/{id}': {
    // `Path` object content
  },
});

In the Path object, you can define the HTTP Methods associated with that path /user/{id}. For example, this is how we define a get method:

const apis = tyrann({
  '/user/{id}': {
    get: {
      path: t.type({
        id: t.number,
      }),
      response: {
        200: t.type({
          name: t.string,
          address: t.string,
        }),
      },
    }
  },
});

Look at Path.path, it describe the values supplied to the path template. /user/{id}.

t.type({
  id: t.number,
})

This description describes exactly the type

interface T {
  id: number;
}

You can also supply parameters to the query string and the body.

const apis = tyrann({
  '/login': {
    post: {
      query: t.type({
        next: t.string,
      }),
      body: t.type({
        username: t.string,
        password: t.password,
      }),
      response: {
        200: t.type({
          successful: t.boolean,
        }),
        403: t.type({
          reason: t.string,
        })
      },
    }
  },
};

By default, the query is created with the default parameters with query-string. You can also supply your own options to queryString (take a look at the API Reference).

As you have already seen, the field response specifies different types with io-ts for diffrent status codes. We generally make it opinionated to define one type for each status code, but you can also use t.union when you have to handle different types. When the response is returned from the server, we first check if the type is defined for the returned status code. It'll raise StatusNotHandled if the status is not defined. Then, it checks the return body (parsed in JSON by default) against the associated type you just defined. It raises BadResponse if such type does not match.

API Invocation

To call the APIs right now, you can handily use apis.<method>.

const response = await apis.get(
  "/user/{id}",
  {
    path: {
      id: 1,
    }
  }
);

In this case, an request GET /user/1 is sent, according to what we supply to path.id. Then you can check the response object to get the result:

const {
  response,        // AxiosResponse<any>
  200: data,       // { name: string, address: string }
} = response;

Generally, response.response is the AxiosResponse object directly passed from the axios.request call. response[<status-code>] is the data returned when the response code is <status-code>.

Now, you have a typed result data and you can confidently believe it is matches the type you just defined!

API Reference

1. tyrann

   import { tyrann } from 'tyrann-io';
   const tyrann = <Apis extends TyrannApis>(apis: Apis, options: TyrannOptions = {}): Tyrann<Apis>;

   tyrann is used to define a set of API object. The result is used to perform API calls with strict type checkings against both the input and output. Check User Guide to have an overall understanding with it.

   You can also customise the behavior by specifying the optional options. options is a TyrannOptions that contains two fields:

   type TyrannOptions = {
     instance?: AxiosInstance;
     axiosRequestConfig?: AxiosRequestConfig | (() => AxiosRequestConfig);
   }

   instance is the AxiosInstance that is used to make API calls. If you don't specify one, we create one for you.

   axiosRequestConfig is passed to axios.request to configure the Axios call. The default is an empty config. If it is passed with an function, the function is called on every request, so you can pass changing headers like Authentication to the configuration. You can also pass baseURL in case that you need to specify the domain rather than the current origin. validateStatus: (s) => s < 500 is useful when you don't want to let axios through an error on 4XX responses. (This will skip io-ts check because axios check happens first. )

2. Tyrann<Apis>.(get|post|put|delete|options|patch)

   const get = async <Name extends Names, Path extends Apis[Name]>(
     name: Name,
     request: Request,
     localOptions: TyrannOptions = options, 
   ): Promise<Response>

   These are the methods of the object returned by tyrann.

   name is path name of the request, which must be one of the path given in the parameter apis when you called tyrann. request is an object that describes the parameters supplied to the request, statically checked against the API definition. The caller is required to fill in query, path, or body according to the definition. Here you can also supply a local TyrannOptions is shallowly merged into the options supplied to tyrann. The response object from the promise and errors that it raises are described in User Guide.

3. omittable

   import { omittable } from 'tyrann-io';
   const omittable = (a: t.Type): t.Type;

   omittable takes a type A and returns its nullable counterpart A | undefined | null.

4. defaultable

   import { defaultable } from 'tyrann-io';
   const defaultable = (a: t.Any, placeholder: P): t.Type

   The missing transformation for types with default values. The caller provides the original typing (with nullable fields), and a new type that encodes an input object with missing values to the object filled by placehoder, is returned.

   const t0 = t.type({
     x: omittable(t.number),
   });
   
   const dft0 = defaultable(
     t0,
     {
       x: 123,
     },
   );
   
   dft0.encode({});
   // { x: 123 }

5. string

   import { string } from 'tyrann-io';
   const minLengthString = h
       .string()
       .min(5, 'Too short. ');

   A string with chainable validations, useful in form validation. The input is string is first checked with 'isString', then checked by chained validators. Check the methods below.

   refine(refiner: (s: string) => boolean, message?: string)

   Chain a custom validator. This validator should return isValid.

   min(n: number, message?: string)

   Check the minimum length.

   max(n: number, message?: string)

   Check the maximum length.

   matches(regExp: RegExp, message?: string)

   Check the string against RegExp.test.

6. taggedUnion

   import { taggedUnion } from 'tyrann-io';
   const schema = taggedUnion([
     {
       tag: t.literal('LWH'),
       length: number().min(5, 'too small'),
       width: number().min(5, 'too small'),
       height: number().min(5, 'too small'),
     },
     {
       tag: t.literal('WV'),
       weight: number().min(5, 'too small'),
       volume: number().min(5, 'too small'),
     },
   ]);

   A special union type of structs tagged with constant strings. Useful if you have 'conditional form', e.g. the user can either input the length & width & height or weight & volume of the stuff, but for each situation all the fields are verified.

Author

👤 Chenyu Wang

• Website: https://blog.chenyu.pw
• Github: @hanayashiki

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