io-ts-koa-middleware

Validate requests with io-ts in your Koa middleware.

Runs provided middleware function only if validations against provided ReqType io-ts runtime type pass, otherwise responds with HTTP 400 and a validation error message.

If decoding succeeds, your middleware will be called with a decoded property set on the ctx parameter. The type signature of ctx.decoded is based on the provided ReqType, which means autocompletion will work and you can safely read from it in your middleware.

import * as t from 'io-ts';
import { decodeRequest } from 'io-ts-koa-middleware';

const ReqType = t.type({
  query: t.type({
    filter: t.string
  }),
});

export const searchMovie = decodeRequest(ReqType)(async (ctx, next) => {
  const { filter } = ctx.decoded.query;
  ...
});

ReqType supports the following properties:

t.type({
  body?: t.Type<any>;
  headers?: t.Type<any>;
  params?: t.Type<any>;
  query?: t.Type<any>;
})

Example

import * as t from 'io-ts';
import { decodeRequest } from 'io-ts-koa-middleware';

const ReqType = t.type({
  headers: t.type({
    authorization: t.refinement(
      t.string,
      apiKey => /^([a-z0-9]){8}$/.test(apiKey),
      'valid OMDB API key',
    ),
  }),
  query: t.type({
    filter: t.string,
  }),
});

export const searchMovie = decodeRequest(ReqType)(async (ctx, next) => {
  const { query, headers } = ctx.decoded;
  const result = await omdb.search(headers.authorization, query.filter);
  ctx.body = { result };
});

$ http localhost:3000/movie/search?filter=avatar "Authorization: apikey42"

HTTP/1.1 200 OK
Connection: keep-alive
Content-Length: 1037
Content-Type: application/json; charset=utf-8
Date: Sun, 18 Nov 2018 08:55:32 GMT

{
    "result": {
        "Actors": "Sam Worthington, Zoe Saldana, Sigourney Weaver, Stephen Lang",
        "Awards": "Won 3 Oscars. Another 85 wins & 128 nominations.",
        "BoxOffice": "$749,700,000",
        "Country": "UK, USA",
        "DVD": "22 Apr 2010",
        "Director": "James Cameron",
        "Genre": "Action, Adventure, Fantasy",
        ...

$ http localhost:3000/movie/search

HTTP/1.1 400 Bad Request
Connection: keep-alive
Content-Length: 142
Content-Type: text/plain; charset=utf-8
Date: Sun, 18 Nov 2018 08:53:47 GMT

Expecting valid OMDB API key at headers.authorization but instead got: undefined.
Expecting string at query.filter but instead got: undefined.