#Fastify

@dotpress/adapter-fastify runs your app on Fastify 5, on Node.js and AWS Lambda.

npm install @dotpress/core @dotpress/adapter-fastify fastify zod

yarn add @dotpress/core @dotpress/adapter-fastify fastify zod

pnpm add @dotpress/core @dotpress/adapter-fastify fastify zod

bun add @dotpress/core @dotpress/adapter-fastify fastify zod

deno add npm:@dotpress/core npm:@dotpress/adapter-fastify npm:fastify npm:zod

import { createApp, defineRoute } from '@dotpress/core'
import { fastifyAdapter } from '@dotpress/adapter-fastify'

defineRoute({ path: '/hello', handler: () => ({ message: 'Hello' }) })

const app = await createApp({ adapter: fastifyAdapter() })
await app.listen(3000)

#Options

#Fastify plugins and hooks

Register Fastify plugins and hooks in beforeRoutes, which can be async: they apply to the Dotpress routes too.

import helmet from '@fastify/helmet'

const app = await createApp({
  adapter: fastifyAdapter({
    beforeRoutes: async (app) => {
      await app.register(helmet)
    },
  }),
})

The instance is ready once createApp() resolves: register everything in beforeRoutes or afterRoutes.

#An existing instance

The app of the Fastify example mounts the Dotpress routes on an existing instance, next to a native route, with a Fastify hook applied to both:

import { fastifyAdapter } from '@dotpress/adapter-fastify'
import { createApp, type Logger } from '@dotpress/core'
import Fastify from 'fastify'
import { createNoteStore } from './notes.ts'
import { notesRouter } from './routes.ts'

/**
 * Mounts the Dotpress routes on a Fastify instance, next to its native
 * routes. Used by the server (`server.ts`) and the Lambda handler
 * (`lambda.ts`).
 */
export const createNotesApp = (options: { logger?: Logger } = {}) => {
  // An existing instance: its plugins, hooks and native routes stay.
  const fastify = Fastify()
  fastify.get('/health', async () => ({ status: 'ok' }))

  return createApp({
    adapter: fastifyAdapter({
      app: fastify,
      // Hooks and plugins registered here apply to the Dotpress routes too.
      beforeRoutes: (app) => {
        app.addHook('onRequest', async (request, reply) => {
          reply.header('x-request-id', request.id)
        })
      },
    }),
    ...(options.logger && { logger: options.logger }),
    routers: [notesRouter(createNoteStore())],
  })
}

#Behavior

• Each Dotpress route is a native Fastify route. Its path (request.routeOptions.url, /users/:id) shows in the Fastify logs, metrics and traces, and a native route with the same method and path fails at startup. Routing still follows the Dotpress rules: trailing slashes ignored, HEAD on GET routes, 405 with Allow.
• Bodies are read by Dotpress, with the same rules on every adapter: the Fastify body parsers only apply to native routes, and @fastify/multipart is not needed for uploads. preParsing hooks apply. Like Fastify, the adapter does not read the bodies of GET and HEAD requests.
• Errors with a 4xx statusCode raised by Fastify or its plugins (@fastify/rate-limit, @fastify/sensible…) use the Dotpress error format and keep their status and message. Other errors are unexpected (500). The adapter takes over the not-found and error handlers of the instance: they apply to native routes too.
• ctx.req.ip is request.ip: proxy headers are only used with the trustProxy option of Fastify, set when you create the instance.
• Streamed responses (stream(), sse()) are written directly to the Node.js response, so that their headers are sent at once: onSend hooks, such as @fastify/compress, do not apply to them.
• ctx.raw is the Fastify request.
• listen(port, host?) listens on every interface without host, like Node.js. close() closes the instance (its onClose hooks), waits for pending requests and closes the streamed responses.

#Testing with inject()

Besides the memory adapter, Fastify tests can use inject(), which goes through the Fastify hooks and plugins without opening a port:

const adapter = fastifyAdapter()
await createApp({ adapter, routers })
const res = await adapter.native().inject('/hello')

#On AWS Lambda

The same app runs on AWS Lambda with createLambdaHandler() of @dotpress/adapter-fastify/lambda: see AWS Lambda.