TypeScript in a monorepo

You can use TypeScript in a monorepo in one of two ways - as a linter, or as a build tool.

In this section, we'll discuss TypeScript's role as a linter. This is when you prevent TypeScript emitting files (with noEmit) and instead use it only to check your source code's types.

Sharing tsconfig.json

We can share TypeScript config files across our repository with a clever solution. We can put our base tsconfig.json files in a single workspace, and extend them from the tsconfig.json files in our apps.

Let's imagine a workspace like this:

apps
├─ docs
│  ├─ package.json
│  ├─ tsconfig.json
├─ web
│  ├─ package.json
│  ├─ tsconfig.json
packages
├─ tsconfig
│  ├─ base.json
│  ├─ nextjs.json
│  ├─ package.json
│  ├─ react-library.json

Our tsconfig package

Inside packages/tsconfig, we have a few json files which represent different ways you might want to configure TypeScript. They each look like this:

packages/tsconfig/base.json
{
  "$schema": "https://json.schemastore.org/tsconfig",
  "display": "Default",
  "compilerOptions": {
    "composite": false,
    "declaration": true,
    "declarationMap": true,
    "esModuleInterop": true,
    "forceConsistentCasingInFileNames": true,
    "inlineSources": false,
    "isolatedModules": true,
    "moduleResolution": "node",
    "noUnusedLocals": false,
    "noUnusedParameters": false,
    "preserveWatchOutput": true,
    "skipLibCheck": true,
    "strict": true
  },
  "exclude": ["node_modules"]
}

Inside package.json, we simply name our package:

packages/tsconfig/package.json
{
  "name": "tsconfig"
}

The other json files in the repository can be accessed via a simple import:

import baseJson from "tsconfig/base.json";
import nextjsJson from "tsconfig/nextjs.json";
import reactLibraryJson from "tsconfig/react-library.json";

This lets us export different config settings for different types of projects.

How to use the tsconfig package

Each app/package which uses our shared tsconfig must first specify it as a dependency:

apps/web/package.json
{
  "dependencies": {
    "tsconfig": "*"
  }
}

Then, they can extend it inside their own tsconfig.json:

apps/web/tsconfig.json
{
  // We extend it from here!
  "extends": "tsconfig/nextjs.json",
 
  // You can specify your own include/exclude
  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx"],
  "exclude": ["node_modules"]
}

Summary

This setup ships by default when you create a new monorepo with npx create-turbo@latest. You can also look at our basic example to see a working version.

Running tasks

We recommend following the setup in the basics section.

Last updated on 2022-10-25T06:38:28.000Z