Core JavaScript development now requires Corepack and Yarn 4

Drupal core uses the Yarn package manager for JavaScript dependency management. Since 2017 Drupal has always used Yarn 1, which is now considered "Yarn classic". Drupal has now upgraded to use Yarn 4.

To start using Yarn 4 locally you need to enable Corepack on the command line, which will allow you to use Yarn 1 and Yarn 4 side-by-side. The packageManager key in package.json determines which version will be used (and falls back to Yarn 1 if not specified).

Corepack ships with all versions of NodeJS supported by Drupal core.

Enabling corepack

Corepack only needs to be enabled once per environment, by running the following command on the command line:

$ corepack enable

Permissions errors

On some systems you may need to run:

sudo corepack enable

Old Yarn versions from other package managers

If Yarn 1 was previously installed by a different package manager, you may receive an error about a Yarn 1 and Yarn 4 mismatch, or a "command not found" error when attempting to enable corepack.

1. First, remove the globally installed version of Yarn 1. For example, for Homebrew:

   brew uninstall
   

2. Then, follow Yarn's instructions for installing corepack:

   npm install -g corepack
   corepack enable