Understanding Kotlin Yarn Lock in KMM Projects

As a Kotlin Multiplatform Mobile (KMM) developer, working with JavaScript (JS) targets is a crucial aspect when building truly cross-platform applications. In this post, we’ll dive into the importance of the yarn.lock file in KMM projects, how it functions, and where it fits within your project structure.

What is yarn.lock?

The yarn.lock file is a critical component in any KMM project that targets JavaScript, whether it's jsBrowser or jsNode. When managing JavaScript dependencies with Yarn, the yarn.lock file locks down the versions of all installed packages, ensuring that every developer and every environment running your project uses the exact same versions. This consistency is vital for avoiding the dreaded "it works on my machine" problem.

Why is yarn.lock Important in KMM?

When building a KMM project, you might need to interact with JavaScript libraries or packages, especially when targeting the web or Node.js. The yarn.lock file ensures that your JS dependencies remain consistent, which is crucial for stable and reliable builds across different environments and teams.

How yarn.lock Fits into Your KMM Project

When working with the JS target in your KMM project, you manage dependencies using Yarn. Here’s how it works:

1. Adding Dependencies:

   Use the command yarn add <package-name> to add new JavaScript dependencies. For example:

   yarn add axios

   This command adds Axios (a popular HTTP client) to your project.

2. Installing Dependencies:

   Running yarn install will install all dependencies listed in package.json, adhering strictly to the versions locked in yarn.lock:

   yarn install

3. Committing to Version Control:

   Ensure both package.json and yarn.lock are committed to your version control system:

   git add package.json yarn.lock
   git commit -m "Added Axios for JS target"
   git push

File Location in Your KMM Project

Typically, you’ll find the yarn.lock file in the root directory of your KMM project, alongside your package.json file. Here’s a sample file structure for clarity:

MyKMMProject/
│
├── package.json
├── yarn.lock
├── build.gradle.kts
├── settings.gradle.kts
├── androidApp/
├── iosApp/
├── shared/
└── jsApp/
    ├── src/
    └── webpack.config.d/

The yarn.lock file is automatically generated and maintained by Yarn, so you don’t need to manually edit it. However, understanding its role and ensuring it’s properly committed is crucial.

Guide: How to Manage yarn.lock in KMM

To give you a practical guide, here’s how you can manage your yarn.lock file in a typical KMM project:

1. Add a New JavaScript Dependency

   Run yarn add <package-name>. For example:

   yarn add axios

   This command adds Axios (a popular HTTP client) to your project.

2. Install Dependencies

   Run yarn install to install all dependencies listed in package.json while ensuring versions locked in yarn.lock are used:

   yarn install

3. Commit Changes

   Ensure both package.json and yarn.lock are committed to your version control system:

   git add package.json yarn.lock
   git commit -m "Added Axios for JS target"
   git push

Reference

• Yarn Documentation: For a deeper understanding of how Yarn works.
• Kotlin Multiplatform Documentation: Official Kotlin documentation on setting up and managing KMM projects.

Visual Guide

Here’s an image illustrating where the yarn.lock file fits within your project structure:

This visual guide will help you quickly locate the yarn.lock file and understand its role within your project.

Conclusion

Understanding and correctly managing the yarn.lock file in your Kotlin Multiplatform Mobile projects is key to maintaining consistent builds and avoiding dependency-related issues. By ensuring this file is correctly maintained and committed, you can ensure that your JS target runs smoothly across all environments.

For more tutorials and guides on KMM development, stay tuned to KMM Programming Nest!