yarnpkg - Should I commit the yarn.lock file and what is it for?

Question

Yarn creates a yarn.lock file after you perform a yarn install.

Should this be committed to the repository or ignored? What is it for?

Answer 1

Yes, you should check it in, see Migrating from npm

Why is it for?
The npm client installs dependencies into the node_modules directory non-deterministically. This means that based on the order dependencies are installed, the structure of a node_modules directory could be different from one person to another. These differences can cause works on my machine bugs that take a long time to hunt down.

Yarn resolves these issues around versioning and non-determinism by using lock files and an install algorithm that is deterministic and reliable. These lock files lock the installed dependencies to a specific version and ensure that every install results in the exact same file structure in node_modules across all machines.