@fastify/response-validation


A simple plugin that enables response validation for Fastify.
The use of this plugin will slow down your overall performance, so we suggest using it only during development.

Install

``
npm i @fastify/response-validation
`

Usage

You just need to register the plugin and you will have response validation enabled:
`js
import fastify from 'fastify'

const app = fastify()

await app.register(require('@fastify/response-validation'))

app.route({
method: 'GET',
path: '/',
schema: {
response: {
'2xx': {
type: 'object',
properties: {
answer: { type: 'number' }
}
}
}
},
handler: async (req, reply) => {
return { answer: '42' }
}
})

app.inject({
method: 'GET',
path: '/'
}, (err, res) => {
if (err) throw err
console.log(res.payload)
})
`

Different content types responses are supported by @fastify/response-validation, @fastify/swagger, and fastify. Please use content for the response otherwise Fastify itself will fail to compile the schema:
`js
{
response: {
200: {
description: 'Description and all status-code based properties are working',
content: {
'application/json': {
schema: {
name: { type: 'string' },
image: { type: 'string' },
address: { type: 'string' }
}
},
'application/vnd.v1+json': {
schema: {
fullName: { type: 'string' },
phone: { type: 'string' }
}
}
}
}
}
}
`

If you want to override the default ajv configuration, you can do that by using the ajv option:
`js
// Default configuration:
// coerceTypes: false
// useDefaults: true
// removeAdditional: true
// allErrors: true

import responseValidator from '@fastify/response-validation'

// ... App setup

await fastify.register(responseValidator, {
ajv: {
coerceTypes: true
}
})
`

You can also pass in an instance of ajv
`js
// Default configuration:
// coerceTypes: false
// useDefaults: true
// removeAdditional: true
// allErrors: true

import responseValidator from '@fastify/response-validation'
import Ajv from 'ajv'

// ... App setup

const ajv = new Ajv()
await fastify.register(responseValidator, { ajv })
`

By default, the response validation is enabled on every route that has a response schema defined. If needed you can disable it all together with responseValidation: false:
`js
import responseValidator from '@fastify/response-validation'

// ... App setup
await fastify.register(responseValidator, {
responseValidation: false
})
`

Alternatively, you can disable a specific route with the same option:
`js
fastify.route({
method: 'GET',
path: '/',
responseValidation: false,
schema: {
response: {
'2xx': {
type: 'object',
properties: {
answer: { type: 'number' }
}
}
}
},
handler: async (req, reply) => {
return { answer: '42' }
}
})
`

Plugins

You can also extend the functionalities of the ajv instance embedded in this validator by adding new ajv plugins.

`js
fastify.register(require('fastify-response-validation'), {
ajv: {
plugins: [
require('ajv-formats'),
[require('ajv-errors'), { singleError: false }]
// Usage: [plugin, pluginOptions] - Plugin with options
// Usage: plugin - Plugin without options
]
}
})
`

Errors

The errors emitted by this plugin are:

- FST_RESPONSE_VALIDATION_FAILED_VALIDATION: This error is emitted when a response does not conform to the provided schema.

- FST_RESPONSE_VALIDATION_SCHEMA_NOT_DEFINED`: This error is emitted when there is no JSON schema available to validate the response.

License

MIT