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.

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>;
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 })),
// ..
)));

For more validation use cases and recipes, visit Validation chapter.

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 });