@marblejs/middleware-io

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A data validation middleware based on awesome io-ts library authored by gcanti.
Installation
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yarn add @marblejs/middleware-io
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Requires @marblejs/core to be installed.
Importing
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// HTTP
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import { requestValidator$ } from '@marblejs/middleware-io';
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​
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// Events, eg. WebSockets
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import { eventValidator$ } from '@marblejs/middleware-io';
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Type declaration
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requestValidator$ :: (RequestSchema, ValidatorOptions) -> Observable<HttpRequest> -> Observable<HttpRequest>
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eventValidator$ :: (Schema, ValidatorOptions) -> Observable<Event> -> Observable<Event>
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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
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export const userSchema = t.type({
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  id: t.string,
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  firstName: t.string,
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  lastName: t.string,
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  roles: t.array(t.union([
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    t.literal('ADMIN'),
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    t.literal('GUEST'),
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  ])),
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});
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​
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export type User = t.TypeOf<typeof userSchema>;
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import { use, r } from '@marblejs/core';
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import { requestValidator$, t } from '@marblejs/middleware-io';
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import { userSchema } from './user.schema.ts';
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​
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const effect$ = r.pipe(
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  r.matchPath('/'),
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  r.matchType('POST'),
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  r.useEffect(req$ => req$.pipe(
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    requestValidator$({ body: userSchema }),
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    // ..
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  )));
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For more validation use cases and recipes, visit Validation chapter.
You can also reuse the same schema for Events validation if you want.
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import { matchEvent, act } from '@marblejs/core';
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import { WsEffect } from '@marblejs/websockets';
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import { eventValidator$, t } from '@marblejs/middleware-io';
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import { userSchema } from './user.schema.ts';
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​
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const postUser$: WsEffect = event$ =>
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  event$.pipe(
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    matchEvent('CREATE_USER'),
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    act(eventValidator$(userSchema)),
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    act(event => { ... }),
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  );
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The inferred req.body / event.payload type of provided schema, will be of the following form:
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type User = {
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  id: string;
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  firstName: string;
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  lastName: string;
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  roles: ('ADMIN' | 'GUEST')[];
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};
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Please note that each eventValidator$ must be applied inside act operator to prevent closing of the main observable stream.
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.
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payload.lastName = false;
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payload.roles = ['TEST'];
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The reported error intercepted via default error effect will look like follows.
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{
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  type: 'CREATE_USER',
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  error: {
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    message: 'Validation error',
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    data: [
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      {
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        path: 'lastName',
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        expected: 'string',
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        got: 'false'
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      },
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      {
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        path: 'roles.0.0',
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        got: '"TEST"',
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        expected: '"ADMIN"'
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      },
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      {
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        path: 'roles.0.1',
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        got: '"TEST"',
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        expected: '"GUEST"'
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      }
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    ]
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  }
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}
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Reporters
You can create custom reporters by conforming to io-ts Reporter interface.
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interface Reporter<A> {
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  report: (validation: Validation<any>) => A
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}
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In order to use custom reporter you have to pass it with options object as a second argument.
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requestValidator$(schema, { reporter: customReporter });
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