Mono TS

• Introduction
• Features
• Install
• Usage
• Monorepo Setup
  • Namespace
  • Packages
  • Apps
  • Services
• Firebase
  • Demo Project
  • Deploying
  • Running Emulators
    • Secrets

Introduction

This is a personal quest for the perfect Typescript monorepo setup.

There is an accompanying article "My quest for the perfect TS monorepo" that you might want to read for context.

It is the best I could come up with given the tooling that is available, so expect this repository to change over time as the ecosystem around Typescript evolves.

My current projects are based on Node.js, Next.js, and Firebase, so that is what I am focussing on primarily. If you use different a different stack, I believe this can still be a great reference, as the approach itself does not depend on it.

Contributions and suggestions are welcome within the scope of this example, but I doubt there ever will be a one-size-fits-all solution, so this code should be viewed as opinionated.

I ended up basing a lot of things on the Turborepo starter, and I recommend reading their monorepo handbook.

Features

• Turborepo to orchestrate the build process and dependencies, including the v2 watch task.
• Multiple isolated Firebase deployments, using firebase-tools-with-isolate
• Firebase emulators with hot reloading
• A web app based on Next.js with ShadCN and Tailwind CSS
• Working IDE go-to-definition and go-to-type-definition using .d.ts.map files
• ESM everything
• Path aliases
• Shared configurations for ESLint v9 with strict type-aware rules
• Simple standard configuration for TypeScript
• Vitest
• Clean, strongly-typed Firestore code for both React (using @typed-firestore/react) and Node.js (using @typed-firestore/server)

Install

In the main branch of this repo, packages are managed with PNPM.

There is also a branch for NPM

Originally, I included branches for Yarn classic (v1), and modern (v4), but I stopped updating them as Yarn is not that commonly used anymore.

I recommended using pnpm over npm or yarn. Apart from being fast and efficient, I believe PNPM has better support for monorepos.

You can install PNPM with corepack which is part of modern Node.js versions:

• corepack enable (if you have not used it before)
• corepack prepare pnpm@latest --activate

Then run pnpm install from the repository root.

Usage

To get started, execute the following 3 scripts with pnpm [script name] from the root of the monorepo:

Script	Description
watch	Continuously builds everything using the Turborepo watch task, except for the web app which has its own dev server
emulate	Starts the Firebase emulators.
dev	Starts the Next.js dev server to build the app on request.

The web app should become available on http://localhost:3000 and the emulators UI on http://localhost:4000.

You should now have a working local setup, in which code changes to any package are picked up.

Monorepo Setup

There is an accompanying article "My quest for the perfect TS monorepo" that you might want to read for context.

This monorepo used to showcase the "internal packages approach" for @repo/common, as described in the article. It lets you link to sources directly without a build step. I removed it because I ran into some issues, and I can not really recommend it anyway. With proper configuration of incremental builds, references, and build orchestration, modern build tools seem to work fast and smoothly anyway.

Namespace

Typically in a monorepo, you will never publish the packages to NPM, and because of that, the namespace you use to prefix your package names does not matter. You might as well pick a generic one that you can use in every private codebase.

At first I used @mono, and later I switched to @repo when I discovered that in the Turborepo examples. I like both, because they are equally short and clear, but I went with @repo because I expect it will become the standard.

Packages

• common Code that can shared across both front-end and back-end environments.
• core Code that is shared between server environments like cloud functions.

Apps

• web A Next.js based web application configured to use Tailwind CSS and ShadCN components.

Services

• fns Various Firebase functions that execute on document writes, pubsub events etc.
• api A 2nd gen Firebase function (based on Cloud Run) serving as an API endpoint. This package also illustrates how to use secrets.

Firebase

In their documentation for monorepos, Firebase recommends putting all configurations in the root of the monorepo. This makes it possible to deploy all packages at once, and easily start the emulators shared between all packages.

Demo Project

Throughout this repository, we use a Firebase demo project called demo-mono-ts A demo project allows you to run emulators for the different components like database without creating a Firebase projects with resources. To make this work you pass the --project flag when starting the emulator, and you need to use a name that starts with demo-.

When passing configuration to initializeApp you can use any non-empty string for the API keys as you can see in apps/web/.env.development.

Deploying

Firebase does not natively support monorepos where packages used shared code from other packages. The Firebase deploy pipeline wants to upload a self-contained package that can be treated similarly to an NPM package, so that it can run an install and execute the main entry from the manifest.

To support shared packages, this repo uses firestore-tools-with-isolate, which is a firebase-tools fork I created to integrate isolate-package. I wrote an article explaining what it does and why it is needed.

This demo can be run using only the emulators, but if you would like to see the deployment to Firebase working you can simply execute npx firebase deploy --project your-project-name the root of the monorepo.

You might notice @google-cloud/functions-framework as a dependency in the service package even though it is not being used in code imports. It is currently required for Firebase to be able to deploy a PNPM workspace. Without it you will get an error asking you to install the dependency. I don't quite understand how the two are related, but it works.

Running Emulators

With the firebase config in the root of the monorepo, you can configure and start the emulators for all packages at once with pnpm emulate.

I have stored these in .env files in the respective service packages. Normally you would want to store them in a file that is not part of the repository like .env.local but by placing them in .env I prevent having to give instructions for setting them up just for running the demo.

Secrets

The api service uses a secret for DEMO_API_KEY. To make secrets work with the emulator you currently have to add the secret to .secret.local and also a .env or .env.local file. See this issue for more info. I have placed it in .env which is part of the repo, so you don't have to set anything up, but .env.local is the proper location probably because that file is not checked into git.