The Joplin source code is hosted on a [monorepo](https://en.wikipedia.org/wiki/Monorepo) managed by Lerna. The usage of Lerna is mostly transparent as the needed commands have been moved to the root package.json and thus are invoked for example when running `npm install` or `npm run watch`. The main thing to know about Lerna is that it links the packages in the monorepo using `npm link`, so if you check the node_modules directory you will see links instead of actual directories for certain packages. This is something to keep in mind as these links can cause issues in some cases.
The list of the main sub-packages is below:
Package name | Description
--- | ---
app-cli | The CLI application
app-clipper | The web clipper
app-desktop | The desktop application
app-mobile | The mobile application
lib | The core library, shared by all applications. It deals with things like synchronisation, encryption, import/export, database and pretty much all the app business logic
renderer | The Joplin Markdown and HTML renderer
tools | Tools used to build the apps and other tasks
There are also a few forks of existing packages under the "fork-*" name.
You can also run it under WSL 2. To do so, [follow these instructions](https://www.beekeeperstudio.io/blog/building-electron-windows-ubuntu-wsl2) to setup your environment.
First you need to setup React Native to build projects with native code. For this, follow the instructions on the [Get Started](https://facebook.github.io/react-native/docs/getting-started.html) tutorial, in the "React Native CLI Quickstart" tab.
To test the extension please refer to the relevant pages for each browser: [Firefox](https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Your_first_WebExtension#Trying_it_out) / [Chrome](https://developer.chrome.com/extensions/faq#faq-dev-01). Please note that the extension in dev mode will only connect to a dev instance of the desktop app (and vice-versa).
To make changes to the application, you'll need to rebuild any TypeScript file you've changed. The simplest way to do this is to watch for changes from the root of the project. Simply run this command, and it should take care of the rest:
You can specify additional parameters when running the desktop or CLI application. To do so, add `--` to the `npm start` command, followed by your flags. For example:
Since Joplin uses Lerna, adding a new dependency should not be done using `npm i -s ...`. Instead you should use the `lerna add` command, which will take care of adding the package while handling the linked packages correctly. For example, to add the package "leftpad" to the "app-desktop" sub-package, you would run:
Note that you should most likely always specify a scope because otherwise it will add the package to all the sub-packages.
## TypeScript
The application was originally written JavaScript, however it has slowly been migrated to [TypeScript](https://www.typescriptlang.org/). New classes and files should be written in TypeScript. All compiled files are generated next to the .ts or .tsx file. So for example, if there's a file "lib/MyClass.ts", there will be a generated "lib/MyClass.js" next to it. It is implemented that way as it requires minimal changes to integrate TypeScript in the existing JavaScript code base.
If you'd like to auto-reload the desktop app on changes rather than having to quit and restart it manually each time, you can use [watchman-make](https://facebook.github.io/watchman/docs/watchman-make.html):
It still requires you to quit the application each time you want it to rebuild, but at least you don't have to re-run `"npm start"` each time. Here's what the workflow loop looks like in practice:
Please read for the [Build Troubleshooting Document](https://github.com/laurent22/joplin/blob/dev/readme/build_troubleshooting.md) for various tips on how to get the build working.
