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middleware-io

A data validation middleware based on awesome io-ts library authored by gcanti.

Installation

$ npm i @marblejs/middleware-io

Requires @marblejs/core to be installed.

Importing

// HTTP
import { requestValidator$ } from '@marblejs/middleware-io';

// Events, eg. WebSockets
import { eventValidator$ } from '@marblejs/middleware-io';

Type declaration

requestValidator$ :: (RequestSchema, ValidatorOptions) -> Observable<HttpRequest> -> Observable<HttpRequest>
eventValidator$ :: (Schema, ValidatorOptions) -> Observable<Event> -> Observable<Event>

Parameters

requestValidator$

parameter definition
schema Partial<RequestSchema>(see io-ts docs)
options <optional> ValidatorOptions

eventValidator$

parameter definition
schema Schema (see io-ts docs)
options <optional> ValidatorOptions

ValidatorOptions

parameter definition
reporter <optional> Reporter
context <optional> string

Usage

Let's define a user schema that will be used for I/O validation.

{% code-tabs %} {% code-tabs-item title="user.schema.ts" %}

export const userSchema = t.type({
  id: t.string,
  firstName: t.string,
  lastName: t.string,
  roles: t.array(t.union([
    t.literal('ADMIN'),
    t.literal('GUEST'),
  ])),
});

export type User = t.TypeOf<typeof userSchema>;

{% endcode-tabs-item %} {% endcode-tabs %}

import { use, r } from '@marblejs/core';
import { requestValidator$, t } from '@marblejs/middleware-io';
import { userSchema } from './user.schema.ts';

const effect$ = r.pipe(
  r.matchPath('/'),
  r.matchType('POST'),
  r.useEffect(req$ => req$.pipe(
    use(requestValidator$({ body: userSchema })),
    // ..
  )));

{% hint style="info" %} For more validation use cases and recipes, visit Validation chapter. {% endhint %}

You can also reuse the same schema for Events validation if you want.

import { matchEvent, use } from '@marblejs/core';
import { WsEffect } from '@marblejs/websockets';
import { eventValidator$, t } from '@marblejs/middleware-io';
import { userSchema } from './user.schema.ts';

const postUser$: WsEffect = event$ =>
  event$.pipe(
    matchEvent('CREATE_USER'),
    use(eventValidator$(userSchema)),
    // ...
  );

The inferred req.body / event.payload type of provided schema, will be of the following form:

type User = {
  id: string;
  firstName: string;
  lastName: string;
  roles: ('ADMIN' | 'GUEST')[];
};

Validation errors

Lets take a look at the default reported validation error thrown by eventValidator$ . Let's assume that client passed wrong values for firstName and roles fields.

payload.lastName = false;
payload.roles = ['TEST'];

The reported error intercepted via default error effect will look like follows.

{
  type: 'CREATE_USER',
  error: {
    message: 'Validation error',
    data: [
      {
        path: 'lastName',
        expected: 'string',
        got: 'false'
      },
      {
        path: 'roles.0.0',
        got: '"TEST"',
        expected: '"ADMIN"'
      },
      {
        path: 'roles.0.1',
        got: '"TEST"',
        expected: '"GUEST"'
      }
    ]
  }
}

Reporters

You can create custom reporters by conforming to io-ts Reporter interface.

interface Reporter<A> {
  report: (validation: Validation<any>) => A
}

In order to use custom reporter you have to pass it with options object as a second argument.

requestValidator$(schema, { reporter: customReporter });
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