A POC on monorepo to manage multi packages and sharable codebase
-
npm install
(installs lerna) -
lerna bootstrap
(connects all the packages) -
npm -C ./packages/usage run start
(console logs "alpha" and "beta" from combind use example module) -
Tree Structure
-
packages
alpha
(deps: []
)beta
(deps: []
)usage
(deps: ["alpha", "beta"]
)
First off, What is lerna
? lerna
is a tool that allows you to maintain multiple npm
packages within one repository.
There's a couple of benefits to this kind of approach, the paradigm is called a monorepo
, and more can be read about it from the source of babel
, and react
.
Here's the gist:
- Single lint, build, test and release process.
- Easy to coordinate changes across modules.
- Single place to report issues.
- Easier to setup a development environment.
- Tests across modules are ran together which finds bugs that touch multiple modules easier.
For this demo I'm going to be using [email protected]
. lerna
is a CLI (command line interface) tool. You're going to want to install it with the --global
(-g
) flag.
npm i [email protected] -g
Then once it's done installing your going to want to run the following
lerna init
This will do a couple of things.
- Creating packages folder.
- Updating package.json.
- Creating lerna.json.
The /packages
folder is where all of your packages belong. Let's go about making a new package alpha
.
cd packages
mkdir alpha
cd alpha
npm init -y
echo "module.exports = 'alpha'" > index.js
Lets go through the same steps for another package beta
.
First go up one directory:
cd ..
Now go about creating beta
.
mkdir beta
cd beta
npm init -y
echo "module.exports = 'beta'" > index.js
Now we're going to create a usage
package that uses both alpha
and beta
as dependencies.
First go up one directory:
cd ..
Now go about creating \usage
.
mkdir usage
cd usage
npm init -y
touch index.js
Open up /packages/usage/index.js
in a text editor and paste this in.
var alpha = require('alpha')
var beta = require('beta')
console.log(alpha + " " + beta)
We're almost there. At this point your whole project should look something like this:
.
├── README.md
├── lerna.json
├── package.json
└── packages
├── alpha
│ ├── index.js
│ └── package.json
├── beta
│ ├── index.js
│ └── package.json
└── usage
├── index.js
└── package.json
What you want to do now is go into /packages/usage/package.json
and add these lines under dependencies
.
{
"dependencies": {
"alpha": "1.0.0",
"beta": "1.0.0"
}
}
Now you need to wire everything up with this command.
lerna bootstrap
The output from this command should look something like this:
Lerna v2.0.0-beta.20
Linking all dependencies
Successfully bootstrapped 3 packages.
Now using the tree
command once more (brew install tree
) we can see the folder structure we can see what lerna
did.
.
├── README.md
├── lerna.json
├── package.json
└── packages
├── alpha
│ ├── index.js
│ ├── node_modules
│ └── package.json
├── beta
│ ├── index.js
│ ├── node_modules
│ └── package.json
└── usage
├── index.js
├── node_modules
│ ├── alpha
│ │ ├── index.js
│ │ └── package.json
│ └── beta
│ ├── index.js
│ └── package.json
└── package.json
It added two stubbed
(my term not lerna
's) modules. If you peak inside /packages/usage/node_modules/alpha/index.js
you can see what I mean.
contents of
./packages/usage/node_modules/alpha/index.js
module.exports = require("/Users/thomas/Desktop/lerna-tutorial/packages/alpha");
Note: This is an absolute path to the module. So if you ever move your lerna project you'll need to rerun
lerna bootstrap
.
And volia! When we run node ./packages/usage/index.js
we get our expected output!
alpha beta
[comment]: # Credit https://github.com/reggi/lerna-tutorial