Fastify plugin to check environment variables

npm i @fastify/env

const fastify = require('fastify')()
const fastifyEnv = require('@fastify/env')

const schema = {
  type: 'object',
  required: [ 'PORT' ],
  properties: {
    PORT: {
      type: 'string',
      default: 3000
    }
  }
}

const options = {
  confKey: 'config', // optional, default: 'config'
  schema: schema,
  data: data // optional, default: process.env
}

fastify
  .register(fastifyEnv, options)
  .ready((err) => {
    if (err) console.error(err)

    console.log(fastify.config) // or fastify[options.confKey]
    console.log(fastify.getEnvs())
    // output: { PORT: 3000 }
  })

You can also use the function getEnvs() of the Request from within a handler function:

fastify.get('/', (request, reply) => {
    console.log(request.getEnvs())
    // output: { PORT: 3000 }
})

Note that the getEnvs decorators will not be added if they already exist.

This module is a wrapper around env-schema. To read an .env file you must set dotenv in the options:

const options = {
  dotenv: true // will read .env in root folder
}

// or, pass config options available on dotenv module
const options = {
  dotenv: {
    path: `${__dirname}/.env`,
    debug: true
  }
}

The @fastify/env plugin loads asynchronously. If you wish to use its values in a different plugin before the boot sequence, you need to make sure that:

1. @fastify/env is registered first.
2. Await the plugin registration or await after()

await fastify.register(fastifyEnv)
// fastify.config can be used in here

OR

fastify.register(fastifyEnv)
await fastify
// fastify.config can be used in here

NB Support for additional properties in the schema is disabled for this plugin, with the additionalProperties flag set to false internally.

In order to have typing for the fastify instance, you should either:

• use the declaration merging technique to enhance the FastifyInstance type with the property and its keys you have defined in the options:

declare module 'fastify' {
  interface FastifyInstance {
    config: { // this should be same as the confKey in options
      // specify your typing here
      FOO: string
    };
  }
}

const fastify = Fastify()
fastify.register(fastifyEnv)

fastify.config.FOO // will be a string
fastify.config.BAR // error: Property BAR does not exist on type { FOO: string }

• use the generic function getEnvs() to get the already typed object:

type Envs = {
  FOO: string
}

const fastify = Fastify()
await fastify.register(fastifyEnv)

const envs = fastify.getEnvs<Envs>() // envs will be of type Envs

envs.FOO // will be a string
envs.BAR // error: Property BAR does not exist on type Envs

If this is the case it is suggested to use json-schema-to-ts to have the type always synchronized with the actual schema.

Kindly sponsored by Mia Platform