FastifyAdapter can't take a FastifyInstance due to a type error

[toptal-dave]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

I am following some example code (that needed adapting) to deploy a Nest.js application using Fastify on AWS Lambda. The code is found in this issue and this PR.

When I adapt the code to be error free, I get a type error at the point where I create the FastifyAdapter using a FastifyInstance:

Argument of type 'FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>' is not assignable to parameter of type 'FastifyHttp2Options<any, FastifyBaseLogger> | FastifyHttp2SecureOptions<any, FastifyBaseLogger> | FastifyHttpsOptions<...> | FastifyInstance<...> | FastifyServerOptions<...>'.
  Type 'FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProviderDefault>' is not assignable to type 'FastifyInstance<any, any, any, FastifyBaseLogger, FastifyTypeProviderDefault>'.
    The types of 'withTypeProvider().decorate' are incompatible between these types.
      Type 'DecorationMethod<FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, Provider>, FastifyInstance<...>>' is not assignable to type 'DecorationMethod<FastifyInstance<any, any, any, FastifyBaseLogger, Provider>, FastifyInstance<any, any, any, FastifyBaseLogger, Provider>>'.
        Target signature provides too few arguments. Expected 2 or more, but got 1.

Minimum reproduction code

https://github.com/toptal-dave/fastify-adapter-type-error

Steps to reproduce

All I did was replace the original code with the following code in the main.ts:

import { NestFactory } from '@nestjs/core';
import {
  FastifyAdapter,
  NestFastifyApplication,
} from '@nestjs/platform-fastify';
import { AppModule } from './app.module';
import awsLambdaFastify, { PromiseHandler } from '@fastify/aws-lambda';
import fastify, { FastifyInstance, FastifyServerOptions } from 'fastify';
import { Context, APIGatewayProxyEvent } from 'aws-lambda';
import { Logger } from '@nestjs/common';

interface NestApp {
  app: NestFastifyApplication;
  instance: FastifyInstance;
}

let cachedNestApp;

async function bootstrap(): Promise<NestApp> {
  const serverOptions: FastifyServerOptions = {
    logger: (process.env.LOGGER || '0') == '1',
  };
  const instance: FastifyInstance = fastify(serverOptions);
  const app = await NestFactory.create<NestFastifyApplication>(
    AppModule,
    new FastifyAdapter(instance),
    {
      logger: !process.env.AWS_EXECUTION_ENV ? new Logger() : console,
    },
  );

  const CORS_OPTIONS = {
    origin: '*',
    allowedHeaders: '*',
    exposedHeaders: '*',
    credentials: false,
    methods: ['GET', 'PUT', 'OPTIONS', 'POST', 'DELETE'],
  };

  app.register(require('fastify-cors'), CORS_OPTIONS);

  app.setGlobalPrefix(process.env.API_PREFIX);

  await app.init();

  return {
    app,
    instance,
  };
}

export const handler = async (
  event: APIGatewayProxyEvent,
  context: Context,
): Promise<PromiseHandler> => {
  if (!cachedNestApp) {
    const nestApp: NestApp = await bootstrap();
    cachedNestApp = awsLambdaFastify(nestApp.instance, {
      decorateRequest: true,
    });
  }

  return cachedNestApp(event, context);
};

Expected behavior

It should be possible to pass a FastifyInstance into FastifyAdapter without causing a type error because it looks like FastifyAdapter takes either options or an instance by the typing:

Package

• I don't know. Or some 3rd-party package
• @nestjs/common
• @nestjs/core
• @nestjs/microservices
• @nestjs/platform-express
• @nestjs/platform-fastify
• @nestjs/platform-socket.io
• @nestjs/platform-ws
• @nestjs/testing
• @nestjs/websockets
• Other (see below)

Other package

@fastify/aws-lambda

NestJS version

10.3.0

Packages versions

{
  "name": "@iluvcoffee/application",
  "version": "0.0.1",
  "description": "",
  "author": "",
  "private": true,
  "license": "UNLICENSED",
  "scripts": {
    "build": "nest build",
    "format": "prettier --write \"src/**/*.ts\" \"test/**/*.ts\"",
    "start": "nest start",
    "start:dev": "nest start --watch",
    "start:debug": "nest start --debug --watch",
    "start:prod": "node dist/main",
    "lint": "eslint \"{src,apps,libs,test}/**/*.ts\" --fix",
    "test": "jest",
    "test:watch": "jest --watch",
    "test:cov": "jest --coverage",
    "test:watch:cov": "jest --watch --coverage",
    "test:debug": "node --inspect-brk -r tsconfig-paths/register -r ts-node/register node_modules/.bin/jest --runInBand",
    "test:e2e": "jest --config ./test/jest-e2e.json"
  },
  "dependencies": {
    "@fastify/aws-lambda": "^3.5.0",
    "@nestjs/common": "^10.0.0",
    "@nestjs/core": "^10.0.0",
    "@nestjs/mapped-types": "^2.0.4",
    "@nestjs/platform-express": "^10.0.0",
    "@nestjs/platform-fastify": "^10.3.0",
    "@nestjs/typeorm": "^10.0.1",
    "aws-lambda": "^1.0.7",
    "class-transformer": "^0.5.1",
    "class-validator": "^0.14.0",
    "fastify": "^4.25.2",
    "fastify-cors": "^6.1.0",
    "pg": "^8.11.3",
    "reflect-metadata": "^0.1.13",
    "rxjs": "^7.8.1",
    "typeorm": "^0.3.17"
  },
  "devDependencies": {
    "@nestjs/cli": "^10.0.0",
    "@nestjs/schematics": "^10.0.0",
    "@nestjs/testing": "^10.0.0",
    "@types/express": "^4.17.17",
    "@types/jest": "^29.5.2",
    "@types/node": "^20.3.1",
    "@types/supertest": "^2.0.12",
    "@typescript-eslint/eslint-plugin": "^6.0.0",
    "@typescript-eslint/parser": "^6.0.0",
    "eslint": "^8.42.0",
    "eslint-config-prettier": "^9.0.0",
    "eslint-plugin-prettier": "^5.0.0",
    "jest": "^29.5.0",
    "prettier": "^3.0.0",
    "source-map-support": "^0.5.21",
    "supertest": "^6.3.3",
    "ts-jest": "^29.1.0",
    "ts-loader": "^9.4.3",
    "ts-node": "^10.9.1",
    "tsconfig-paths": "^4.2.0",
    "typescript": "^5.1.3"
  },
  "jest": {
    "moduleFileExtensions": [
      "js",
      "json",
      "ts"
    ],
    "rootDir": "src",
    "testRegex": ".*\\.spec\\.ts$",
    "transform": {
      "^.+\\.(t|j)s$": "ts-jest"
    },
    "collectCoverageFrom": [
      "**/*.(t|j)s"
    ],
    "coverageDirectory": "../coverage",
    "testEnvironment": "node"
  }
}

Also, the output of npx nest info:

 _   _             _      ___  _____  _____  _     _____
| \ | |           | |    |_  |/  ___|/  __ \| |   |_   _|
|  \| |  ___  ___ | |_     | |\ `--. | /  \/| |     | |
| . ` | / _ \/ __|| __|    | | `--. \| |    | |     | |
| |\  ||  __/\__ \| |_ /\__/ //\__/ /| \__/\| |_____| |_
\_| \_/ \___||___/ \__|\____/ \____/  \____/\_____/\___/


[System Information]
OS Version     : Linux 6.6
NodeJS Version : v18.19.0
NPM Version    : 10.2.3 

[Nest CLI]
Nest CLI Version : 10.2.1 

[Nest Platform Information]
platform-express version : 10.3.0
platform-fastify version : 10.3.0
mapped-types version     : 2.0.4
schematics version       : 10.0.3
typeorm version          : 10.0.1
testing version          : 10.3.0
common version           : 10.3.0
core version             : 10.3.0
cli version              : 10.2.1

Node.js version

18.19.0

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

No response

[toptal-dave]

Do you think a better approach would be to use the getHttpAdapter or getHttpServer or similar from the returned promise to get the Fastify server?

[toptal-dave]

I was able to fix the code myself using the nestApp.getHttpAdapter().getHttpServer() to get the instance:

import { NestFactory } from '@nestjs/core';
import {
  FastifyAdapter,
  NestFastifyApplication,
} from '@nestjs/platform-fastify';
import { AppModule } from './app.module';
import awsLambdaFastify, { PromiseHandler } from '@fastify/aws-lambda';
import { Context, APIGatewayProxyEvent } from 'aws-lambda';
import { Logger } from '@nestjs/common';

let cachedNestApp;

async function bootstrap(): Promise<NestFastifyApplication> {
  // Create the app
  const app = await NestFactory.create<NestFastifyApplication>(
    AppModule,
    // Use an env var to set the logger to nest or console
    new FastifyAdapter({ logger: (process.env.LOGGER || '0') == '1' }),
    {
      logger: !process.env.AWS_EXECUTION_ENV ? new Logger() : console,
    },
  );

  // Enable cors
  app.enableCors({
    origin: '*',
    allowedHeaders: '*',
    exposedHeaders: '*',
    credentials: false,
    methods: ['GET', 'PUT', 'OPTIONS', 'POST', 'DELETE'],
  });

  // Set the prefix as necessary
  app.setGlobalPrefix(process.env.API_PREFIX);

  await app.init();

  return app;
}

export const handler = async (
  event: APIGatewayProxyEvent,
  context: Context,
): Promise<PromiseHandler> => {
  // If there's no cached app
  if (!cachedNestApp) {
    // Bootstrap
    const nestApp: NestFastifyApplication = await bootstrap();
    // Create an AWS Lambda Fastify cached app from the Nest app
    cachedNestApp = awsLambdaFastify(nestApp.getHttpAdapter().getHttpServer(), {
      decorateRequest: true,
    });
  }

  return cachedNestApp(event, context);
};

I know it's a separate issue but it would be pretty cool to get the serverless documentation updated with a proper example of how to run a Fastify-based Nest.js application in a Lambda. I'm trying this specific solution to reach a balance of speed (which lowers cost in Lambdas) & avoiding running an instance anywhere (as a container or an EC2) to demonstrate and MVP for a project with Nest.js. It's pretty cool to think that you could start a project this way and when traffic increases, with a few small tweaks, you could probably migrate to EKS or Kubernetes.

[toptal-dave]

Actually I don't think that fixes it entirely because when I try to run the code as a containerized Lambda created by SST, I get the following error:

2023-12-31T23:36:48.020Z	5f37cec7-815e-4f51-a59d-7a20e93c69cf	ERROR	Invoke Error 	{
    "errorType": "TypeError",
    "errorMessage": "app.decorateRequest is not a function",
    "stack": [
        "TypeError: app.decorateRequest is not a function",
        "    at module.exports (/var/task/node_modules/@fastify/aws-lambda/index.js:23:9)",
        "    at Runtime.handler (/var/task/dist/main.js:28:50)",
        "    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)"
    ]
}

There's a demo repo here. Perhaps using getHttpAdapter().getHttpServer() isn't the way to get an instance after all...

[kamilmysliwiec]

Your local fastify dependency version must match the one installed by the @nestjs/platform-fastify package

[toptal-dave]

@kamilmysliwiec thanks for the response! I'm going through the fundamentals course now so it feels like I'm replying to a celebrity!

Anyway, I took your advice and locked the version to 4.25.1; however, I'm still getting the decorate response error:

The error is as follows:

2024-01-05T11:53:49.911Z	3c1d2db4-a768-4e91-ba05-44c73b9982e2	ERROR	Invoke Error 	{
    "errorType": "TypeError",
    "errorMessage": "app.decorateRequest is not a function",
    "stack": [
        "TypeError: app.decorateRequest is not a function",
        "    at module.exports (/var/task/node_modules/@fastify/aws-lambda/index.js:23:9)",
        "    at Runtime.handler (/var/task/dist/main.js:28:50)",
        "    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)"
    ]
}

I think my next step is actually going to be to abandon the serverless Fastify adapter and see if I can get it working without. I was able to recently deploy to AWS via an ECS+EC2+ASG+ALB setup but for demo-ing and early growth, Lambda would be extremely awesome.

[toptal-dave]

Actually, @kamilmysliwiec , when I restored the code to a prior version that declared the instance separately instead of trying to reference it (here), I was able to get it working. Thanks for the help!