Technical Guidelines

Technical Guidelines for developers

Lerna

Lerna is a popular tool for managing JavaScript projects with multiple packages, optimizing the workflow around managing multi-package repositories with git and your package manager.

Installation

Before you can use Lerna, you need to install it globally on your machine:

npm install --g lerna

Basic Usage

1. Bootstrap the project We use a thing called Workspaces to link any cross-dependencies. This allows us to install all node_modules for each package, and also hoist common dependencies to the root of your project. This was previously done by using lerna bootstrap but the bootstrap command got deprecated in favour of the NPM solution. This process is done by running:

npm install

2. Add a new package You can add a new package to the monorepo with the lerna create command:

lerna create package-name

3. Installing modules To install dependencies across all packages in a Lerna-managed monorepo, you can use the lerna add command. This command adds a package to the packages in the monorepo.

lerna add package-name --scope=some-package

Replace package-name with the name of the package you want to install, and some-package with the name of the specific package(s) you want to add the dependency to. If you want to add the dependency to all packages, you can omit the --scope flag:

lerna add package-name

This command will add the specified package as a dependency in all of your Lerna packages.

FAQ

If I add a module inside the package.json of the monorepo, will it be added to all packages?

No, adding a module to the package.json of the root of your monorepo will not automatically add it to all of your packages. The root package.json and the package.json files in each package are separate. If you add a module to the devDependencies or dependencies in the root package.json, it will only be installed at the root level. It will not be available to the individual packages unless you specifically import it in those packages.

Can I run all tests inside the project simultaneously?

Yes, you can use the lerna run test command or more specifically call one of the test-scripts defined in the root package.json of the monorepo.

"scripts": {
    "test:unit": "lerna run test:unit",
    "test:integration": "lerna run test:integration",
}