When utilizing internal packages in a Turborepo project, frontend projects like Next.js function smoothly and can utilize internal packages without issues thanks to the `transpilePackages` configuration option.

However, backend projects like NestJS encounter errors when attempting to import internal packages directly.

e.g. error  

```bash
"C:\Program Files\nodejs\npm.cmd" run start

> nest@0.0.1 start
> nest start               

Error: Cannot find module '@repo/database'
Require stack:
```

This issue can be circumvented by compiling internal packages to JavaScript before importing.

## Solution

### 1. Install `tsup` in the Internal Package

```bash
npm i -D tsup -w <workspace>
```

e.g. For an internal package named `data-access-db` (assuming it uses PrismaClient):

```bash
npm i -D tsup -w packages/data-access-db
```

### 2. Modify the Internal Package's `package.json`

Configure the build command to export JavaScript files to the `dist` folder.

`package.json`

```json
  "main": "./dist/index.js",
  "module": "./dist/index.mjs",
  "types": "./dist/index.d.ts",
  "scripts": {
    "build": "tsup src/index.ts --format cjs,esm --dts",
    "dev": "npm run build -- --watch"
  },
```

### 3. Build & Install the Internal Package Before Starting NestJS Project

```bash
npm run build -w <workspace>
npm i
```

e.g.  

```bash
npm run build -w packages/data-access-db
```

As rebuilding the internal package every time you start NestJS is cumbersome, it's advisable to prepare a script in the top-level `package.json` to build and install internal packages before starting the NestJS project.