Minimal usage of Lerna in independent mode

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Lerna is powerful package which allow develop multiple module in one repository, this approach named monorepo. There are many cool things which can do Lerna, but in this post I describe only minimal usage.

I use Packagist for PHP packages and it has great feature where I can mark module as dev-master in composer.json and Composer will upload code directly from Github with .git directory, but unfortunately npm does not have this feature. That is why I started to use Lerna for NodeJS packages. Now I can develop absolutely independent packages in one project and Lerna help me to organize it.

Getting started

lerna is a CLI package. You’re going to want to install it with the --global (-g) flag.

$ npm i lerna -g

Now, I’m going to create new directory where independent packages will be placed.

$ mkdir my-project
$ cd my-project
$ lerna init --independent

This will do a couple of things:

  • Creating packages folder.
  • Updating package.json.
  • Creating lerna.json.

The packages/ directory is where all your packages belong. Let’s go about cloning your package from Github.

$ cd packages/
$ git clone https://github/popovserhii/scrapoo

Now go about creating usage/. You can imagine it as your project where another packages will be used.

$ mkdir usage
$ cd usage
$ npm init -y
$ touch index.js

What you want to do now is go into packages/usage/package.json and add these lines under dependencies.

  "dependencies": {
    "scrapoo": "0.1.0",

Here is important moment you must take real package version from packages/scrapoo/package.json and append it to a package which relies on your package.

Now you need to wire everything up with this command. Go to root directory of my-project and run

$ lerna bootstrap

The output from this command should look something like this:

Lerna v3.1.0
Linking all dependencies
Successfully bootstrapped 2 packages.

After that scrapoo will be append as dependency to node_packages of usage/ and it will be linked with scrapoo from packages/ directory. You can develop packages independent, make commits and push to Github and in the same time use this packages together. You can add any number of packages to packages/ and use them as dependencies in another packages and Lerna help you with correct linking between them.

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