💉 Fastify inject tRPC

Plugin for Fastify that allows to use the Fastify inject API with the full power of tRPC types

Installation

Install with npm or yarn or pnpm

npm install fastify-inject-trpc
# or
yarn add fastify-inject-trpc
# or
pnpm add fastify-inject-trpc

Motivation

This library was created for testing tRPC procedures with Fastify as a server. This solution is better than tRPC caller, because this plugin allows to use Fastify ecosystem and don't create custom context for testing, it will be automatically generated by tRPC like in real request.

Features

• Allows to inject tRPC procedures calls with fastify inject API
• Fully type safe procedures calls
• Very similar API to Fastify's inject

Limitations

• Subscriptions are not supported at this time
• Custom serializers are not supported at this time

Usage

import fastify from 'fastify'
import { z } from 'zod'
import { initTRPC } from '@trpc/server'
import {
  fastifyTRPCPlugin,
  FastifyTRPCPluginOptions,
} from '@trpc/server/adapters/fastify'
import { fastifyInjectTRPCPlugin } from 'fastify-inject-trpc'

// 1. Init TRPC
const t = initTRPC.create()

// 2. Create router
const appRouter = t.router({
  greeting: t.procedure
    .input(z.object({ name: z.string() }))
    .query(({ input: { name } }) => {
      return `Hello, ${name}!`
    }),
})

type AppRouter = typeof appRouter

// 3. Create Fastify builder
async function buildFastify() {
  // 3.1. Create Fastify instance
  const app = fastify()

  // 3.2. Register fastifyTRPCPlugin
  app.register(fastifyTRPCPlugin, {
    prefix: '/trpc',
    trpcOptions: {
      router: appRouter,
    },
  })

  // 3.3. Register fastifyTRPCInjectorPlugin and await it (https://fastify.dev/docs/latest/Reference/Plugins/#asyncawait)
  await app.regester(fastifyTRPCInjectorPlugin, {
    router: appRouter,
    prefix: '/trpc',
  })

  return app.withTypedTRPCInjector<AppRouter>()
}

const app = await buildFastify()

// 4. Inject a tRPC procedure call
const response = await app.injectTRPC((router) =>
  router.greeting({ name: 'World' }),
)
const json = response.json()

// Before using it you should check that response didn't return any error
if ('result' in json) {
  const greetingStr = json.result.data
  // ^?
  // Type of greetingStr would be a string
}